Weil-McLain boiler troubleshooting

If you can hardly find operating manual from a Weil boiler received during a purchase, just visit our site. Here you will always find the necessary information on Weil McClain boiler troubleshooting. It is essential for diagnostics and repairs of your device. Just look into the table below.

Weil-McLain Ultra Commercial boiler troubleshooting

The Weil-McLain Ultra lineup comprises several gas-fired water boilers varying in capacities and design. Commercial models from the Ultra range are intended for use in a restaurant, hotel, or other commercial institution. If anything goes wrong with the appliance (for instance, it won’t start or won’t heat the water properly), refer to the table below for quick troubleshooting help.

Problems	Cause	Solutions
Message displayed	Condition causing automatic reset	Reset action
Display fault	Display communications out for 30 seconds	Resets automatically when communication is re-established
Automatic reset limit open	Set if auto reset limit open	Reset after auto reset is closed for 2.5 minutes Reset with manual reset on display
Supply water temperature high	Set if the supply water temperature is higher than 200 °F	Reset after heat exchanger oudet temperature is less than burner on temperature Reset with manual reset on display
Return water temperature high (heat exchanger input)	Set if the return water temperature is higher than 200 °F	Reset after heat exchanger inlet temperature is less than burner on temperature Reset with manual reset on display
Return water temperature greater than supply water temperature	Set if heat exchanger inlet temperature is higher than the heat exchanger outlet temperature +10 F	Reset when return temperature minus 9 °F is less than supply temperature or Reset with manual reset on display
Supply water rising too fast	Set if supply water temperature rises faster than 2 °F per second	Reset after 1 minute delay Reset with manual reset on display
Supply greater than return by 58 °F	Set if current heat exchanger outlet temperature is greater than the heat exchanger inlet temperature + 58 T	Reset after 0.5 minute delay Reset with manual reset on display
Temperature sensors	Supply sensor open or shorted Return sensor open or shorted Set if flue sensor not balanced (more than 10 °F difference between sensors) Set if heat exchanger outlet sensor not balanced (more than 10 °F difference between sensors)	Reset if sensors balance
Flue temperature high	Set if flue temperature over 210 °F	Reset after 1.5 minute delay
LWCO fault	Set if UVCO open goes to manual reset lockout if open more than 1 second	Reset when closed

Weil-McLain SlimFit boiler troubleshooting

Boilers that belong to Weil-McLain SlimFit range vary greatly, yet they have one feature in common: all of these appliances are comparatively small. Due to this, they occupy less space, and, therefore, can be used when free space is a problem. High efficiency condensing boilers are intended for commercial and institutional settings.

Display	Condition	Diagnostics	Corrective actions
Nothing shown on display screen and blower running at full speed	Control is not receiving 24V power	Check wiring for short circuit or incorrect wiring.	• Correct wiring per wiring diagram including connection of transformer.
		Check 2-amp low voltage fuse on transformer	• Replace fuse with proper part found in replacement part section of this manual. If fuse blows again recheck wiring per diagram.
Nothing is shown in display screen and no other boiler components are operating	Control is not receiving 120V power	Check sen/ice switch and/or circuit breaker to boiler turned is on.	• Turn on service switch to power boiler.
		Is there 120 Volts at the service switch?	• Troubleshoot and correct the power supply to the service switch.
		Is the SlimFit ON/OFF POWER SWITCH located on top of the boiler turned on?	• Turn the SlimFit power switch on top of the boiler to ON.
		Check for 120 volts at the line voltage terminal block located inside the control pod.	• Correct wiring inside the control pod using the wiring diagram in this manual.
Nothing is shown on display screen, but boiler is operating	Occurs when power is lost from the Sola module to the display.	Check for loose connections and proper pin alignment/engagement in the main harness and the back of the display circuit board.	• Check for continuity on the wire harness from the display to the SlimFit. See repair parts section for proper replacement part.
		Cycle power off and on using boiler power switch and check for operation.	• Replace with new display module. See repair parts section for proper replacement part.
Boiler Icon not shown on display	Occurs when the communication is lost from the Sola to the display.	Display has been disconnected from Sola Control	• Reconnect and perform synchronization process
		Check for loose connections and proper pin alignment/engagement in the main harness and the back of the display circuit board.	• Check for continuity on the wire harness from the display to the SlimFit. See repair parts section for proper replacement part.
Boiler Icon Black on display	Occurs when the communication is lost from the Sola to the display.	Display has been disconnected from Sola Control	• Reconnect and perform synchronization process
		Check for loose connections and proper pin alignment/engagement in the main harness and the back of the display circuit board.	• Check for continuity on the wire harness from the display to the SlimFit. See repair parts section for proper replacement part.
Outlet T-Rise Limit	Occurs when supply water temperature in heat exchanger rises faster than 2°F per second.	Automatically resets after 5 minute delay or using manual reset on display.	• Verify water piping is installed correctly using primary/secondary connection to the boiler loop. Verify that piping methods and sizes comply with the instructions in this manual. • Verify proper pump sizing for boiler size and system require- ments. • Verify boiler pump is energized • See message displayed Inlet sensor fault or outlet sensor fault and follow procedure for loose connections.
Delta-T inlet/outlet limit	Boiler Out temperature has exceeded the Boiler In temperature by more than 58°F	Automatically resets after 15 second delay or using manual reset on display.	• Verify water piping is installed correctly using primary/secondary connection to the boiler loop. Verify that piping methods and sizes comply with the instructions in this manual.
		After 20 automatic resets occur in the same heat demand the boiler will need a manual reset.	• Verify proper pump sizing for boiler size and system require- ments. • Verify boiler pump is energized • See message displayed Inlet sensor fault or outlet sensor fault and follow procedure for loose connections.
Inlet/outlet inversion limit	Occurs when a return water temperature is greater than the corresponding supply temperature for 5 minutes during run.	Manual reset required.	• Verify proper flow direction of the boiler pump. This pump should be installed to push water through the boiler's return pipe as shown in Figure x Verify proper placement of system sensors for single or multiple boiler systems. System sensors should be on system piping not on the boiler loop. System sensors may need to be located further away from boiler loop connection to the system if proximity to the boiler loop is causing sensors to be heated inaccurately.
Inlet Sensor fault; Outlet Sensor fault; Header Sensor fault; Stack Sensor fault; Outdoor sensor fault	Occurs when a temperature sensor has electrically shorted or has become disconnected.	Automatically resets if sensors begin reading temperatures.	• Check all the temperature readings of the boiler on the Boiler Icon-Diagnostics-Analog I/O and determine if any sensors are currently displayed as SHORT or OPEN. • Determine which sensors are suspect and measure their resis- tance value and compare it to the values shown If the resistance values are incorrect, replace the temperature sensor. • OUTDOOR/HEADER are the optional outdoor air temperature and system water temperature sensors. If these are not being used they will always be shown as OPEN. This is normal unless the sensors were installed. • Check wire harness for loose connections and pin engagement at sensor connection, chassis mount connection through sheet metal cabinet, and Sola Control module. Unplug connection at sensor and at Sola control and check continuity between ends. • If problem persists after checking items above replace Sola Control.
	Occurs when dual temperature sensors values have spread by more that 6°F	Automatically resets when sensors are within 6°F.	• Follow procedure for above for SHORT and OPEN sensor condi- tions to properly diagnose sensor. If measured resistance values of sensors convert to temperatures separated by more than 6°F replace the sensor.
Stack Limit	Occurs when flue temperature sensor exceeds 216®F	Automatically resets after 5 minute delay.	• Follow procedure for above for SHORT and OPEN sensor condi- tions to properly diagnose sensor. In addition inspect heat exchanger combustion chamber and flue ways for abnormal wear or buildup. • Inspect vent system for abnormal wear or damage. • Contact Weil-McLain Technical Support.
Outlet High Limit	Boiler outlet temperature sensor reached 200°F	Reset with manual reset on display	• Verify all isolation valves are open and pumps are programmed into the Sola Control properly. • Verify water piping is installed correctly using primary/secondary connection to the boiler loop. Verify that piping methods and sizes comply with the instructions in this manual. • Verify proper pump sizing for boiler size and system reguire- ments. • Verify boiler pump is energized
Flame detected out of sequence	Occurs when flame is detected when there should be no flame	Reset with manual reset on display	• See message displayed Inlet sensor fault or outlet sensor fault and follow procedure for loose connections. • Verify FLAME value on the (Boiler Icon) screen guickly goes to zero when the gas valve closes. • Check for flame at burner via flame current with burner off. Turn boiler off and watch flame through observation port. If flame continues after shutdown replace gas valve and venturi.
Flame lost early in run or Flame lost in run. Light off rate proving failed; Purge rate proving failed; Fan speed failed during prepurge; Fan Speed failed during preignition; Fan speed failed during ignition; Fan Speed failed during run; Fan movement detected during standby	Flame lost after ignition	Automatically resets after 5 minute delay.	• Check gas supply pressure Inspect flame sense electrode and wiring
	Blower unable to reach required speed or does not reach 0 RPM when turned off.	Reguires a manual reset.	• Check wire harness for loose connections and pin engagement at blower connections, chassis mount connection through sheet metal cabinet, and Sola module. Unplug connection at sensor and at Sola and check continuity between ends. Blower is con- nected to both low voltage and line voltage harness. • Check FAN Boiler Icon-Diagnostics-Analog I/O screen with boiler in standby mode and blower not running. If BLOWER SPEED is not 0 RPM then replace blower. • If blower does not rotate during ignition sequence check for 120V power at blower connection. If 120Vac power at blower motor and it doesn't start replace blower. Check power at Blower relay. If 120Vac is not present at Relay when boiler is powered replace Relay.
Ignition Failed	Boiler went through 2 ignition attempts and never detected flame A fault has occurred in the control hardware	Reguires a manual reset.	• Fouled, worn, bent, or faulty igniter or flame sense rod. Fouled igniters and flame sensors can be cleaned for additional use with fine grit sand paper or steel wool. Worn or badly fouled igniters and flame sense rods should be replaced with the proper repair part. Igniter rods should be parallel with a 3.0mm (0.118in) spark gap. • Dirty burner and/or heat exchanger will cause high back pressure and poor ignition. Follow procedure in maintenance section of this manual to clean burner and heat exchanger using flue cleaning tool and rinse method. • Visual inspection of flue ways will often will not be able to diagnose conditioa
			• Check combustion settings on high and low fire and adjust per setup instructions if necessary.
			• Check incoming gas pressure with boiler off. at high fire, and at low fire. Adjust within limits on rating label.
			• Verify high altitude settings have been changed for installations 5,500 ft above sea level.
			• Check ignition cable resistance. Should measure 1000 Ohms (+/- 50 Ohms)
			• Check continuity of flame sense cable.
			• Check ignition transformer is plugged in. If no spark present dur- ing ignition replace spark transformer
			• Check for flue pipe and intake pipe restrictions or blockage
			• Check burner fasteners and gaskets
			• Check venturi gaskets
			• Check condensate trap for blockage allowing condensate to accumulate inside heat exchanger
Internal Fault		Reguires a manual reset.	• Reset control. If fault returns replace Sola control
ILK OFF (Flue Pressure)	Flue pressure switch is opened during run	Reguires manual reset.	• Check for flue pipe and intake pipe restrictions or blockage
			• Check continuity of flue pressure switch and flue pressure switch wiring
ILK OFF (Block Temperature)	Block temperature switch reached 203°F	Reguires manual reset	• Verify water piping is installed correctly using primary/secondary connection to the boiler loop. Verify that piping methods and sizes comply with the instructions in this manual.
			• Verify proper pump sizing for boiler size and system reguire- ments.
			• Verify boiler pump is energized
			• See message displayed Inlet sensor fault or outlet sensor fault and follow procedure for loose connections.
ILK OFF (Gas Pressure Low)	Low gas pressure switch is open	Requires manual reset of low gas pressure switch and Sola Control	• Check gas supply pressure, adjust regulator to specification
ILK OFF (Gas Pressure High)	High gas pressure switch is open	Requires manual reset of high gas pressure switch and Sola Control	• Check gas supply pressure, adjust regulator to specification 100% Lockup regulator required
ILK OFF (Low Water Level)	Occurs when Low Water Cutoff Device detects Low water condition	Requires manual reset of low water cutoff and Sola control.	• Check for low water condition in system.
			• If low water condition does not exist check Low water level Boiler Icon-Diagnostics-Digital I/O screen to view status of Low Water Cutoff. If shown as OFF check wiring between LWCO and Sola.
			• Probe may be checked by grounding the tip of the probe to the heat exchanger. If fault continues after reset, replace LWCO probe
ILK OFF (External Limit)	Occurs when external limit opens (ILK).	Requires manual reset	• Is there an external safety device connected? If yes, trouble shoot the external limit to determine and correct the cause that opened the limit. Also check for loose wiring connections.
			• If no external safety devices are installed, remove the top cover and ensure a jumper is installed between ILK terminals on terminal block
LCI OFF (Min Air Flow Switch)	Min air flow switch is opened during run	Automatically resets.	• Check for flue pipe and intake pipe restrictions or blockage
			Check continuity of flue pressure switch, normally open switch (no air flow) Check minimum air flow switch relay in control tray.Terminals 4 and 5 should be normally closed, when gas valve energizes terminals 4 and 5 should open Check continuity of minimum air flow switch relay wiring
LCI OFF (Load Control Input)	Occurs when external limit opens (LCI).	Automatically resets. Boiler will not enter prepurge until LCI is closed	• Is there an external safety device connected? If yes, trouble shoot the external limit to determine and correct the cause that opened the limit. Also check for loose wiring connections.
			• If no external safety devices are installed, remove the top cover and ensure a jumper is installed between LCI terminals on terminal block
Pll OFF (Pre- Ignition ILK)	Occurs when external limit opens (Pll).	Requires manual reset. Ignored during run	• Is there an external safety device connected? If yes, trouble shoot the external limit to determine and correct the cause that opened the limit. Also check for loose wiring connections.
			• If no external safety devices are installed, remove the top cover and ensure a jumper is installed between Pll terminals on terminal block

Weil-McLain ULTRA ULTRA-105 Control Supplement boiler troubleshooting

Weil-McLain ULTRA ULTRA-105 is a gas-ﬁred water boiler with a summer/winter switch feature. If desired, you may disable the space heating circulator during the warmer time of the year. It is equipped with the Ultra control module, due to which the target outlet water temperature is increased without your intrusion in case a call for heat lasts longer than 10 minutes.

Boiler not firing and:	Check for:	Corrective actions:
Display first digit shows a number from 1 to 8. Last digits show 2 or 3-digit number (boiler outlet water temperature).	This is normal operation.	Boiler is in normal operating mode.
Display first digit shows the number 6; other 2 or 3 digits show boiler water temperature	Boiler water temperature may have exceeded limit — the boiler will restart after the water temperature has dropped below limit setting (parameter 4) minus the differential.	If boiler water temperature is above parameter 4, the boiler shut down on limit.
	The control module may have lost flame signal — if so, boiler should restart.	If the boiler water temperature is NOT above parameter 4, the control may have lost flame signal. Flame signal (DC volts from low voltage terminal strip terminal 9 to ground) should be at least 4 VDC.
		Verify adequate gas flow — check incoming gas pressure. If ac- ceptable, check gas line size, gas regulator or any possible cause of reduced pressure.
		A lower flame signal may indicate a fouled ignitor or damaged ignitor insulation. Follow procedure in Ultra Boiler manual to check igni- tion electrode wiring and inspect and clean the ignition electrode. Replace the ignition electrode and wiring if necessary.
		If problem persists, obtain a maintenance kit for the boiler
Display flashes 9, then b. Last two digits show code number.	Display is showing a lockout code.
Control display is blank	Is 120 vac present at terminals 1 and 2 of line voltage terminal strip?	If not, check external line switch and fuse or breaker.
	Blower running on high, and F1 fuse blown?	Turn power off to boiler. Remove power wiring to circulator(s) at boiler terminal strip. Replace the Fl fuse. Then turn power on to boiler. If blower stops running and display works properly, replace defective circulator(s) and retry.
		If the blower continues to run after checking step 2, above, turn power off to the boiler. Inspect wiring and high voltage terminal strip for defects. Replace if necessary. Then retry.
		If the problem persists after above steps, replace the control mod- ule.
Display shows U124 or U125	Display stays on U124 or U125	Check transformer. If good: • Turn off power to the boiler. • Disconnect thermostat wires at boiler. • Replace F3 fuse. • Determine cause of fuse failure on 24-volt system. • Replace defective part and retry.
		If problems persists, check low voltage terminal strip and wire har- ness. Replace if necessary. Retry.
		If problem persists, replace control module.
Display first digit shows 0 and last digits show 2 or 3-digit number (boiler outlet water temperature).	Are room thermostat and DHW aquastat satisfied?	If yes, then boiler should be off — there is no call for heat. Turn up thermostat or aquastat. Boiler should start.
	Is room thermostat or DHW aquastat calling for heat?	Check parameters 2 and 3. • To change to Parameter mode, press the MODE button one time when in Standby mode. • Parameter 2 must be ON for DHW operation — (2 01] on display. • Parameter 3 must be ON for central heating operation — [3 01J on display.
	Does display intermittently show 0 for outlet water temperature?	Check parameters 1 and 3. • To change to Parameter mode, press the MODE button one time when in Standby mode. If parameter 1 shows 68: • Press “+” until display returns to 140. • Then press “Store.” • Display will blink when setting is accepted and stored. If parameter 3 shows 00: • Press “+” and display will return to “01 ” • Then press “Store.” • Display will blink when setting is accepted and stored. If problem persists, replace the control module.
	Is blower running on low?	From Standby mode, press “Mode” twice and display will change to “Info” • Press “Step” until display shows #6. • If #6 value displays as 32, replace the blower assembly.
	Is room thermostat or DHW calling for heat, but boiler is not firing?	Check thermostat or aquastat: • Turn off power to the boiler. • Install a temporary jumper on low voltage terminal strip termi- nals 5 and 6 for central and terminals 3 and 4 for DHW. • Retry. If boiler operates, check the thermostat or aquastat and connect wiring. Replace if necessary. • Remove jumper and retry.
		Check boiler wiring: • Turn off power to the boiler. • Check wiring against wiring diagram. Verify all wiring is in good condition and securely fastened. • Replace harness if necessary and retry.
		If boiler still does not fire, replace the control module.
	Check information mode, #4 — does display show 4.230?	The outdoor sensor has failed or the wires are shorted. Replace the outdoor sensor if wiring is ok. Also, remove the outdoor sensor wires and check operation to ensure no other problem is occurring.

Code	Reason for soft lockout	Corrective actions (pressing RESET should restart boiler immediately)
18	High limit operation — burner off until outlet water temp drops below 203 °F minus the ON differential	This should only happen when the heat demand is lower than the lowest firing rate of the boiler, such as operation of a single, small zone. Check system for:
		Verify boiler and system are full of water
		Make sure system does not have trapped air preventing proper flow
		Inspect and verify system piping and components (including pipe size and circulator capacity)
		Verify piping agrees with boiler manual recommendations.
		Verify proper circulator(s) operation
		Possible loose connector on boiler outlet sensor. Tighten connector
		Possible bad boiler supply outlet sensor
19	Return water temperature higher than 203 °F. — burner off until return water temp drops below 203 °F minus the ON differential	Verify proper direction of water flow through boiler
		Verify boiler and system are full of water
		Make sure system does not have trapped air preventing proper flow
		Inspect and verify system piping and components
		Verify piping agrees with boiler manual recommendations.
		Verify proper circulator(s) operation
		Possible loose connector on boiler outlet sensor. Tighten connector
		Possible bad boiler supply outlet sensor
24	Return temp higher than supply temp — Burner off waiting for supply temp to rise above return temp	Verify proper direction of water flow through boiler
		Verify boiler and system are full of water
		Make sure system does not have trapped air preventing proper flow
		Inspect and verify system piping and components
		Verify piping agrees with boiler manual recommendations.
		Verify proper circulator(s) operation
		Possible loose connector on boiler outlet sensor. Tighten connector
		Possible bad boiler supply outlet sensor
25	Outlet water temp rose too quickly — burner off for 10 minute wait (burner recycles, increasing wait 1 minute each attempt, to a max of 15 minutes)	Possible hot water return from DHW tank.
		Make sure system does not have trapped air preventing proper flow.
		Inspect and verify system piping and components.
		Verify piping agrees with boiler manual recommendations.
		Verify proper circulator(s) operation.
		Possible loose connector on boiler outlet sensor. Tighten connector.
		Possible bad boiler supply outlet sensor.
26	External limit open on limit wired in soft lockout circuit (auto reset). Low voltage terminals 6 and 7. Burner off for 150 seconds	If no external limit connected to 6 & 7, verify green jumper ware making good electrical contact with screw* terminals.
		If external limit connected, verify proper limit operation.
29	Blower signal not zero when it should be — Burner off until signal condition corrected	Change display to Information mode — if INFO #6 shows 6._32, the blower has failed.
		Possible strong wind blowing against vent turning blowrer wheel, correct venting.
		Defective blowrer.
		Defective control module.
30	Temperature rise across boiler more than 45°F. — Burner off for 150 second wait (plus 1 additional minute for each failed attempt, up to 20 times, then hard lockout occurs	Flow problem through boiler — Temperature rise through boiler should be less than 35°F.
		Make sure system does not have trapped air preventing proper flow'.
		Inspect and verify system piping and components (including pipe size and circulator capacity).
		Verify piping agrees with boiler manual recommendations.
		Verify proper circulator(s) operation.
		Possible loose connector on boiler supply/return sensor(s). Tighten connector.
		Possible bad supply/return sensor — replace sensor.
35	Short circuit across flue temperature sensor terminals — Burner off until corrected	Shorted wiring to flue sensor— correct the wiring.
		Defective flue sensor — replace sensor.
40	Open circuit across flue temperature sensor terminals — Burner off until corrected	Shorted wiring to flue sensor— correct the wiring.
		Defective flue sensor — replace sensor.
52	Flue Temperature exceeded 216 °F. but did not exceed 225 °F (hard lockout occurs above 225 °F — Burner off for 150 second wait	Verify flue temperature with thermometer. If actual temperature does not correlate with Information mode #5 replace flue sensor.
		Heat exchanger may need to be cleaned.
		Burner problem — verify gas pressure, burner firing rate and combustion per Ultra Boiler manual procedures — correct any problems. If combustion is not acceptable
65	Waiting for blower to start	Change display to Information mode — if INFO #6 shows 6._32, the blower has failed.
		Verify blow'er wiring, 120 VAC on high voltage connector, if no 120V AC, inspect/replace wire harness, or control module.
		Defective blowrer.
		Defective control module.
0	Flame detected on startup	Igniter may be cracked. Moisture gets in crack and may cause E-00.
		Burner may be operating too hot due to incorrect combustion. Inspect flame during operation following the procedure in Ultra Boiler Manual. If flame is acceptable at both high and low fire, go to step 3, below. If flame is not acceptable: • For propane boilers, verify propane orifice is correct and properly installed. See Ultra Boiler Manual for procedure. Obtain and install propane orifice if necessary. • For correctly-orificed propane boiler or natural gas boiler, replace gas valve if burner glows excessively.
		Look into the burner inspection window after the boiler shuts down. If flame is still present, gas valve may be leaking. Replace gas valve. BEFORE replacing valve check gas line pressure coming to boiler. Pressure must not exceed 13 inches w.c. or valve damage could occur.
2	Ignition failed through 5 attempts: NO spark occurs:	Check ignition electrode cable, electrode connector, spade connection at MCBA and other connections. • Inspect ignition electrode cable and electrode for insulation damage. • Resistance of igniter wire should be 1000 ohms +/- 50 ohms. If resistance is more or less, replace igniter wire. • Check ground lead from ground terminal strip to heat exchanger access cover.
2	Ignition failed through 5 attempts: Spark occurs, but no flame:	Verify manual gas valve in boiler is open.
		(Models 80 or 105 only) — Verify plastic line from gas valve to air inlet elbow is con- nected to gas valve and elbow, and line is unobstructed, with no kinks
		Check incoming gas pressure per Ultra Boiler Manual. If gas pressure is too high, the gas valve regulator will lock up.
		Verify gas lines are free of obstruction.
		Purge gas lines of air if necessary.
		Verify flue gas vent and air supply piping are correctly installed, in good condition and there are no obstructions.
		Check voltage to gas valve. It should be approximately 19 to 21 vdc during ignition attempt.
		Check gas meter to verify gas flows when gas valve is activated.
		Remove and inspect/clean ignition electrode per Ultra Boiler Manual. Clean white oxides if necessary. Replace ignition electrode if in poor condition or cannot be cleaned.
		Ensure vent is clear. Restricted vent will not allow boiler to light.
2	Ignition failed through 5 attempts: Spark occurs, but no flame:
		Remove condensate drain and check drain fitting on bottom of heat exchanger and condensate trap for restriction. • If restricted, clean and let condensate water out. • Re-connect and fire boiler.
		Clean the heat exchanger
		See Ultra Boiler manual or the instructions in this guide for procedure to disconnect gas valve from venturi. • Inspect venturi gas line to verify there are no obstructions. • Reinstall gas valve.
		Check for possible flue gas recirculation at vent/air terminations or inside boiler hous- ing. Look for signs of moisture, corrosion in the venturi or water dripping from the burner.
		If gas valve is powered, gas flows when activated, and above have been verified, replace the gas valve and retry.
2	Ignition failed through 5 attempts: Flame occurs, but flame signal strength is low (less than 4 vdc between low voltage terminal strip terminal 9 and ground):	Inspect flame per procedure in Ultra Boiler manual, at low fire and high fire rates. Remove and inspect/clean ignition electrode per Ultra Boiler Manual. Clean white oxides if necessary. Replace ignition electrode if in poor condition or cannot be cleaned. Inspect and clean burner if necessary • Replace burner if not in good condition. Check gas flow rate at gas meter with boiler at high fire (see Ultra Boiler manual for procedure to force boiler to high fire). If input is not within about 10% of boiler rating, replace gas valve. • Note that the length of the vent/air piping will affect boiler firing rate, with longer piping causing lower inputs. Check ground wire and connections from ground terminal strip to heat exchanger access cover and from ground terminal strip to XI-6 terminal on the wiring harness. • Use ground continuity meter to verify good ground path. Follow procedure in Ultra Boiler manual to inspect and clean ignition electrode. • Replace ignition electrode if necessary. If above does not correct problem, replace control module.
3	Ignition failure or gas valve electrical problem	If error occurs before boiler tries for ignition, problem may be gas valve connection or harness. Measure continuity of gas valve harness through outer 2 pins of connector. Measure resistance between outer two pins on gas valve — should be approximately 50 ohms. Resistance from each pin to ground must be infinity. If error occurs after 5 ignition retries, Replace control module.
4	Voltage lost after lockout occurred or AC voltage fluctuations on incoming power	"Control module will only restart with manual reset, even after power loss. • Code 04 occurs if power is interrupted while another error is present or due to power input fluctuations. " Incoming power fluctuations may cause MCBA module to go into E-04 hard error code. • This can occur due to power failure, brown-out or poor electrical input from a back- up generator. • To reduce shutdowns due to poor power conditions, install Weil-McLain part number 383-500-021, Time Delay Relay (3 minute incoming power time delay) to give incom- ing power time to stabilize before powering boiler. In severe cases of power fluctuations, Time Delay Relay may not solve E-04. • If so, very good incoming power line filter or Uninterruptible Power Source (UPS) may correct.
5	Internal Control or Display error	Replace display and display ribbon cable.
		Replace control module.
6	Internal Control Failure	Reset control and retry. If problem persists, replace control module.
7	Gas valve relay error	Gas valve wiring may be shorted to ground. Check continuity to ground Defective gas valve. Measure resistance between outer two pins on gas valve — should be approximately 50 ohms. Resistance from each pin to ground must be infinity.
8	Internal Control Failure	Reset control and retry. If problem persists, replace control module.
9	Internal Control Failure	Reset control and retry. If problem persists, replace control module.
11	EEPROM Error	Ignition interference. Replace control module.
12	External limit open (between terminal 6 and 8)	Check low water cut-off, limit controls, etc. wired between terminals 6 and 8.
13	Usually indicates a sensor problem	Measure the resistance of each of the sensors
14	Supply water sensor problem	Measure the resistance of each of the supply sensor.
15 16 17	Internal control failure	Reset control and retry. If problem persists, replace control module.
18	Thermal overrun condition - Outlet water temperature above 210 °F.	This should only happen when the heat demand is lower than the lowest firing rate of the boiler, such as operation of a single, small zone. Check system for:
		Verify boiler and system are full of water.
		Make sure system does not have trapped air preventing proper flow.
		Inspect and verify system piping and components.
		Verify piping agrees with boiler manual recommendations.
		Verify proper circulator(s) operation.
		Possible loose connector on boiler outlet sensor. Tighten connector.
		Possible bad boiler supply outlet sensor.
		Use a contact thermometer to check outlet water temperature.
		• Compare to temperature shown with display in Info mode
		• Replace return temperature sensor if results are not close.
		• Replace control module if sensor replacement doesn’t solve problem.
19	Thermal overrun condition - Return	Verify boiler and system are full of water
	water temperature above 210 °F.	Make sure system does not have trapped air preventing proper flow'
		Inspect and verify system piping and components
		Verify piping agrees with boiler manual recommendations.
		Verify proper circulator(s) operation and direction
		Possible loose connector on boiler outlet sensor. Tighten connector
		Possible bad boiler return boiler inlet sensor
25	Temperature rise > 58°F	Check flow.
		Check pipe size and circulator capacity. Follow suggestions for hard lockout code 18.
28	Blower not running	Change display to Information mode — if INFO #6 shows 6._32, the blower has failed.
		Verify 120 volts at blower connection — If no 120 VAC, inspect wiring. Replace control module if wiring is correct and in good condition.
		If 120VAC is present, remove low voltage wiring harness.
		If blowrer does not run, replace the blower. If blower runs, replace the control module.
29	Blower signal not zero when it should be	Change display to Information mode — if INFO #6 shows 6._32, the blower has failed.
		This might happen if the vent is facing a very windy side of the building. If the blowrer is turning because of the wind wrhen a call for heat initiates on the Ultra, an E-29 might occur. Move the vent to a less windy location
		Check the wiring. Replace blower.
		Replace control module.
30	Temperature rise across boiler over 58 °F, and occurred 20 times.	Flow problem through boiler — Temperature rise through boiler should be less than 35 °F.
		Make sure system does not have trapped air preventing proper flow.
		Inspect and verify system piping and components.
		Verify piping agrees with boiler manual recommendations.
		Verify proper circulator(s) operation.
		Possible loose connector on boiler supply/return sensor(s). Tighten connector.
		Possible bad supply/return sensor.
31	Outlet water temperature sensor short circuit.	Inspect outlet water temperature sensor and wiring. Replace sensor if wiring correct and in good condition. Replace low voltage wiring harness if problem persists. Replace control module if harness replacement doesn’t resolve.
32	Return water temperature sensor short circuit.	Inspect return water temperature sensor and wiring. Replace sensor if wiring correct and in good condition. Replace low voltage wiring harness if problem persists. Replace control module if harness replacement doesn’t resolve.
36	Outlet water temperature sensor open circuit.	Inspect outlet water temperature sensor and wiring.
		• Replace sensor if wiring correct and in good condition.
		• Replace low voltage wiring harness if problem persists.
		• Replace control module if harness replacement doesn’t resolve.
37	Return water temperature sensor open circuit.	Inspect return water temperature sensor and waring.
		• Replace sensor if wiring correct and in good condition.
		• Replace low voltage wiring harness if problem persists.
		• Replace control module if harness replacement doesn’t resolve.
44	Internal control failure	Reset control and retry. If problem persists, replace control module.
52	Flue temperature exceeded 225 °F.	Verify flue temperature wath thermometer.
		• If actual temperature does not correlate with Information mode #5, replace flue sensor
		Heat exchanger may need to be cleaned
		Burner problem — verify gas pressure, burner firing rate, combustion. Correct prob- lems.
60	Internal control failure	Reset control and retry. If problem persists, replace control module.
61	Internal control failure	Reset control and retry. If problem persists, replace control module.
65	Blower signal too low (not enough driving force)	Inspect wiring and connections.
		• If wiring is correct, replace blower assembly.
		• If blower assembly replacement is unsuccessful, replace control module.

Weil-McLain WGO boiler troubleshooting

WGO is a series of oil-fired water boilers produced by Weil-McLain, which is a division of the Marley-Wylain Company specializing in hydronic heating systems. The WGO lineup includes dedicated water-only oil boilers with cast iron sections. Some of the features include quick open top and swing-away burner door, two flue outlets, and recessed target wall.

Common Problems	Common Causes	Possible Corrections
Rapid cycling — burner turns on and off frequently.	Thermostat installed where drafts or heat affect reading.	Locate thermostat on inner wall away from heat sources or cool drafts.
	Heat anticipator in thermo- stat adjusted incorrectly.	Adjust heat anticipator to match current draw.
	Incorrect limit setting.	Have qualified service technician increase limit setting to decrease cycling. Maximum setting 220° F.
Need to frequently add makeup water.	Leaks in boiler or piping.	Have qualified service technician repair leaks at once to avoid constant use of makeup water.
Popping or percolating noise heard in boiler.	Mineral deposits in sections due to constant use of make- up water, or incorrect pH.	Have qualified service technician de-lime boiler, repair leaks at once to avoid constant use of makeup water and check pH (between 7.0 and 8.5).
Black water condition.	Oxygen corrosion due to leaks in piping.	Have qualified service technician repair leaks at once to avoid constant use of makeup water and check pH (between 7.0 and 8.5).
Frequent release of water through relief valve.	Expansion tank sized too small or water-logged.	Have qualified service technician check expansion tank operation.
Metal flakes found in flueway.	Contaminated combustion air supply.	Remove sources of hydrocarbons in or near boiler area. (Bleaches, cleaners, chemicals, sprays, fabric softeners, paint remover, etc.)
	Condensation of combustion gases.	Have qualified service technician check boiler operation.
Some radiators or baseboard units do not	Air in system.	Bleed air from system through air vents in radiators or baseboard units.
heat or are noisy.	Low system pressure.	Have qualified service technician check for leaks in boiler or piping at once.
	High limit set too low.	Have qualified service technician adjust limit to higher setting.
Domestic water from tankless heater is hot then suddenly turns cold. OR Domestic water from tankless heater is always lukewarm.	Mineral deposits insulate internal waterways of heater.	Have qualified service technician delime or replace coil.
	Boiler stop-leak compound has been added to boiler wa- ter and is insulating outside of coil.	Have qualified service technician remove and clean coil and drain, and flush boiler to remove stop-leak.
	Incorrect mixing valve setting for tankless heater.	Have qualified service technician adjust mixing valve setting.
	Domestic flow rate too high.	Have qualified service technician install flow check valve set to rating of tankless heater.
	Incorrect setting on tankless heater control.	Have qualified service technician raise tankless control setting. Adjust differential on tankless control to lower setting.