| Burner Motor won’t Run – T-stat Calls for Heat | 1. Check the electrical supply to the furnace. |
| 2. Verify the furnace furnace On-Off switch is in the ON position. |
| 3. Defective thermostat circuit – white and red thermostat low voltage leads (M1/M5M, M1/M5B models). If the burner motor or combustion fan runs, check: |
| • Thermostat connections |
| • Thermostat |
| 4. No voltage to control module – determine if 24 volts (or 120 volts) is available to the control module. If voltage is not available check for: |
| • Blown fuse, defective transformer, circuit breaker, no electrical supply. |
| • Limit switch open. |
| • Loose connections |
| Combustion Blower Runs – No Flame | 1. Defective centrifugal switch (M1B Model). |
| • Check the operation of centrifugal switch by removing end bell of the burner motor. |
| • Clean contacts of motor. |
| • Ifthe contacts are closed, replace the motor. |
| 2. Defective pressure switch (M1M – 077 & 090 Models) – check air tube and electrical connections. |
| 3. Burner in purge mode – allow 75 seconds for flame establishing period. |
| 4. Check for proper electrical connections at purge timer, control box, or gas valve. |
| 5. Check for gas supply – gas line valve on, control lever on |
| 120 VAC Is Available At AMP Plua – lanitor Does Not Heat Up | 1. Disconnect power to the furnace. |
| 2. Disconnect AMP plug to the ignitor, and check ignitor resistance with an ohm meter. Set on RX1 scale. |
| • Normal reading should be 40 – 75 ohms. |
| • If above or below this rating at room temperature change ignitor. |
| 3. Check for continuity from ignitor receptacle to burner |
| Control Module is Powered – lanitor won’t Heat Up | 1. Disconnect ignitor leads at AMP receptacle and check for 120 volts at the plug during ignition sequence. |
| 2. Replace ignition control if 120 volts is not available at AMP plug during ignition sequence. |
| Main Flame Ionites – Burner Locks Out | • Ignition control is not properly grounded. |
| • Defective ignition control. |
| • Improper polarity of 120 volt power supply. |
| • Ignitor has hairline crack. |
| • Improper gas pressure or burner air adjustment is not allowing flame to contact ignitor tip for flame rectification. |
| • Misaligned ignitor does not allow flame to contact ignitor tip for flame rectification |
| Burner Short Cvclino – Thermostat Calls for Heat. Limit Switches Closed | • Check for polarity. |
| • Check ground. |
| • Check flue. |
| • Check combustion air. |
| • Check gas pressure. |
| • Check orifice. |
| • Check the position of ignitor, a normal reading should be 40-75 ohms |
| 24 Volts Supplied To Gas Valve Durina lanition – No Main Gas Flow | • Gas valve may be defective. Replace if necessary. |
| • Gas piping may be plugged. Check for adequate gas supply to gas valve at union |
| Burner Operates – Insufficient Heat | • Check thermostat for proper setting and location. Thermostat should not be located where it will be affected by another heat source. |
| • Check for clean filter and proper air flow. |
| • Check burner for proper gas firing rate. |
| • Be sure unit is not undersized for its thermal load. |
| • Check thermostat anticipator. The nominal setting is 0.4. |
| Circulation Air Blower Will Not Operate Even Thouoh The Burner Does Operate | • Check thermostat G connection. |
| • Check wiring to motor. |
| • Check for a defective motor |
| Burner Flame Without Motor Runnina | • Gas valve stuck open, check gas valve for proper operation (replace if necessary) and inspect heat exchanger. |
| • Check for 115 volts to the combustion blower motor; replace if necessary. |
| • If no power to combustion blower then check wiring and control module; replace if necessary. |