Furnace starts properly, then shuts down, led flashes 8 times
Goodman GMH95 natural gas furnace appears as though the integrated curcuit board is not detecting the flame, and is shutting off the gas valve at the same moment the circulator fan starts. I suspect the timing is the same because both are set to occur 30 seconds after startup. Unit will cycle again of it's own accord, but never burns over 30 seconds. Any ideas?
- If you need clarification, ask it in the comment box above.
- Better answers use proper spelling and grammar.
- Provide details, support with references or personal experience.
Tell us some more! Your answer needs to include more details to help people.You can't post answers that contain an email address.Please enter a valid email address.The email address entered is already associated to an account.Login to postPlease use English characters only.
Tip: The max point reward for answering a question is 15.
You are on the right track. I would suggest you change the sensor though as if it has failed it would be one of the reasons why it is shutting down the way it is as it cannot detect the flame and is closing the solenoid.
Fan purge for 30-45 seconds. During this time, a pressure switch is actuated by the running of the purge fan, proving the control board the purge fan is running.
After purge and purge prove, the hot surface ignition and or spark begins. After a few second delay, the gas valve will open. The control board then monitors for flame prove through another sensor located near the burners. If there is no flame within 3-5 seconds, the gas valve closes. It will repeat this process, usually 3 times, before it shuts the system down, which requires a power down of the system to reset.
I have seen trash get into the hose between the purge blower and the purge switch. But you could be having other problems.
No, the board isnt out. The board has a code telling you that its out. Its your flame sensor. You wouldn't have gotten any heat if the gas valve was out. check if that flame sensor goes to another sensor on the same circuit , if it does check that. If it just a one wire sensor make sure its in the right position. If its a one rod flame senor with one wire I would sand it down with sandpaper. if its a two wire senor ohm it out to see if you ger current going through it.
you either need an ignitor...even though it gets red it may not get hot enough...just repaired one doing the samething yours is doing same model number as yours. If that is not the problem the only other thing it could be is the circuit board
Furnace fails to operate.
• Integrated control module
diagnostic LED is
flashing ONE (1) flash.
• Furnace lockout due
to an excessive
number of ignition
“retries” (3 total)1.
• Failure to establish flame.
Cause may be no gas to
burners, front cover
pressure switch stuck open,
bad igniter or igniter
alignment, improper orifices,
or coated/oxidized or
improperly connected flame
• Loss of flame after establishment.
Cause may be
interrupted gas supply, lazy
burner flames (improper gas
pressure or restriction in flue
and/or combustion air
piping), front cover pressure
switch opening, or improper
induced draft blower
• Locate and correct gas
• Check front cover
operation (hose, wiring,
Correct if necessary.
• Replace or realign
• Check flame sense
signal. Sand sensor if
coated and/or oxidized.
• Check flue piping for
length, elbows, and
• Verify proper induced
draft blower performance.
The unit uses "flame rectification" (basically it is sensing a pulsing dc current) to sense the flame and is very sensitive to bad/poor ground and also to a dirty flame sensor. The gas ignition does not shut off the valve ...the board is not sensing the current thru the flame so its reading a "no Fire" fault and shutting down.
Clean the flame sensor with sandpaper till its brite and shiny and check all connections to make sure they are tight and very clean, especially the ground to the board and also to the furnace itself (sometimes we have to actually drive a ground rod near the furnace itself or use some other means to make sure that a proper gorund is achieved).
If still have a problem; I would try another board, the flame sensor is just a piece of solid stainless alloy wire so its really not necessary to change it unless the ceramic insulator is cracked.
Before you buy another board, I would suggest that you have a pro look at it.
If your igniter comes on but no ignition, that eliminates the possibility of a bad or clogged pressure switch, high limit or flame rollout switch. Sounds to me like you have a control board, or a gas valve going bad. Could even be some loose, corroded, or faulty wiring. Before the igniter comes on the furnace does a self diagnostics to ensure everything is working, or the furnace will not make it to the igniter sequence. Inducer motor, pressure switch/s, limit controls are closed…then comes on the ignitier, gas valve opens, pilot runners and burners ignite, flame sensor detects the flame, blower comes on and all operations are working.