Ducane Furnace Error Codes

Here you can find detailed description of Ducane furnace error codes. The errors are mostly signalized by LED flashes and signals, and the tables contain the numbers and frequency of the flashes to understand what is wrong with Ducane furnace.

Each error signal is described with details or status related to this. There are separate tables made for different modifications because the meaning will be different in each case. For example, with Ducane FITS-ALL 92V the 8 flashes will mean lockout due to too many flame dropouts. Depending on Ducane furnace LED fault codes you can make your decision or conclusion on the nature of the issue.

Ducane CMPB075C3B Furnace Error Codes


LED Cause / Solution
Steady OFF Internal control fault or no power
Steady ON Normal operation, no call for heat
Fast Flash Normal operation, call for heat present
1 flash Pressure switch does not close within 30 seconds of inducer energized.
Pre-Purge – The control energizes the induced draft motor and waits for the pressure switch to close. If the pressure switch does not close within 30 seconds of the inducer energizing, the control will flash “1″ on the LED. The control will leave the inducer energized indefinitely as long as the call for heat remains and the pressure switch is open.
2 flashes Pressure switch is closed before inducer is energized.
Call for Heat – The control checks to see if the pressure switch is open. If the pressure switch is closed, the control will flash “2” on the LED and wait indefinitely for the pressure switch to open.
3 flashes Limit switch is open
Limit Operation – The limit switch is ignored unless a call for heat is present (W energized). If the limit switch is open and a call for heat is present, the control de-energizes the gas valve and runs the indoor blower motor on heat speed, and runs the induced draft motor. The control will flash “3″ on the LED until the limit switch closes. When the switch re-closes or the call for heat is lost, the control runs the induced draft motor through post-purge and runs the indoor blower through the selected fan off delay. The control will return to normal operation after the blower off delay is completed.
4 flashes In lockout from failed ignitions or flame losses
Ignition Retry – If flame is not established on the fifth trial for ignition (initial try + 4 re-tries), the control de-energizes the gas valve and goes into lockout. The control flashes a “4” on the LED to indicate ignition failure lockout.
5 flashes Twin communications fault
A Twin Communications Fault will occur if the 24 VAC supply to the twins are not in phase with each other, or power is removed from one of the twins. While a Twin Fault exists, the control does not respond to thermostat commands and flashes “5” on the status LED. Open limit and undesired flame response are still operational. The control continually tries to establish communication and automatically resumes normal operation when communication is re-established. If a twin fault occurs during a heat cycle, both furnaces terminate the call for heat immediately. The only chance for blower mis-synchronization is if the blower off delays are set differently on the twins. If a twin fault occurs during high speed fan or continuous fan, both controls shut blowers off immediately.
6 flashes Limit Switch tripped 5 times during heat cycle
Limit Operation – If the limit switch has 5 trips per call for heat, the control will go into a hard lockout and the LED will flash “6″. Lockout may be manually reset by removing power from the control for more than 1 second or removing the thermostat call for heat for more than 1 and less than 20 seconds
7 flashes 5 flames losses during one heat cycle.
Ignition Re-Cycle – The control will re-cycle up to 5 flame losses (4 re-cycles) within a single call for heat before going to lockout. The LED will flash “7“ during this lockout.

Ducane FITS-ALL 92V Furnace Error Codes

LED Status Fault Description
LED Off No power to control or control hardware fault detected
LED On Normal operation
1 Flash Flame Present with gas valve off
2 Flashes Pressure switch closed with inducer off
3 Flashes Low-fire pressure, rollout, or aux limit switch open
4 Flashes High limit switch open
5 Flashes Not used
6 Flashes Pressure switch cycle lockout
7 Flashes Lockout due to no ignition
8 Flashes Lockout due to too many flame dropouts
9 Flashes Incorrect polarity and phasing

Ducane MPGAV100B4 Furnace Error Codes

LED Status Description
LED Off No demand for high heat
LED On High heat demand, operating normally
LED Flashing High heat demand, high pressure switch not closed