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I have the subject furnace and recently replaced the pressure switch. Now when I turn on the furnace it will cycle 3 times and shut down. The control module light now flashes 4 times. Do know what the problem may be now?

Thanks

The board in your furnace is a 903429. Below are the codes for that board:

Red light:
Steady on - OK
Rapid Flash - False flame or internal control fault.
1 Flash - Limit switch open.
2 Flash - Pressure switch open w/ inducer on.
3 Flash - Pressure switch closed w/ inducer off.
4 Flash - Lockout due to failed ignition.
5 Flash - Reversed polarity.

Yellow Light:
Steady On - Good flame signal.
Blinking - Weak flame signal.
Steady Off - No flame signal.

What can be the causes of failed ignition?

Hi,

3 most common are the Hot Surface Ignitor, Remote Flame Sensor or the Gas Valve.


I believe your furnace HSI is also the flame sensor, would have to look to be sure .


Thanks,
Robert

my furnace will run its heat cycle like its supposed to then when it shuts off the fresh air fan stays on for 10
seconds then the blower will kick on with no fault lights ever

Hi,

Please start a new thread and then delete this post. We keep threads to original poster for ease of following.


Thanks,
Robert