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?
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Hi, on the board you will have a 3 to 5 amp fuse, plug in type just like your auto fuses. It probably blew it which shuts power down on the furnace. It kill power to the thermostat also. If the furnace would try and start and shut back off, you will have what is called a flame sensor that runs along side of the pilot. It is white porcelein, round about about 5" long with a metal tip coming out the end. The other end plugs on the board. The metal tip is in the pilot flame and when they get dirty they will shut the unit off very fast. You can use steel wool to clean the tip or real fine grade sanding cloth. After cleaning this flame sensor it continues to cycle on and off, you should have a led light on the board that will flash. It may have a number of flashes, for instance 4 flashes long and 2 short ones what ever the amount. On the inside of the panel, you will have a code chart and it will point you to the problem according to how many times it flashes. They almost trouble-shoot them selves. If you remove the panel, most have a kill switch on them for safety. So, when you take it off and you have no power to anything and the fuse is good, this door panel switch is around the perimeter that opens the contacts just like your home refrigerator does for the light but works backward the that. Tape it down and it will restore power so you can leave the panel off when checking this out. This will be a easy fix for you. Please keep me posted and be kind when rating me as I know you will. Let me know the outcome as I keep all of your information on hand. Sincerely, Shastalaker7 A/C, Heating, & Refrigeration Contractor PS Be sure to remove tape if you have a switch and make sure the panel is installed right so it closes the switch. Best to you.
Check if your thermostat is set on 'o fan' setting.
If it is, trey to set it on 'Auto-fan' instead.
since it seem as if the heating does go off,only the fan may be running continuously.
this is possible if the thermostat is incorrectly set or installed.
had similar problems with same furnace. I think the 3 blinks is high limit event. either way with the power off to the furnace remove the board from the 4 clips holding it on one at a time then turn it over and look at it you will be able to tell if the board is bad because it will appear scortched and the resin will be bubbled up where it went bad. replace board and you will be fine. went through 2 in 2 years all of a sudden they are being made by a different company from the original and the 1st replacement. now all is fine. Take a good picture of the board close up so you can reconnect all the wires properly. Friend of mine got it from a wholesaler for $55.00
Goodman's control boards are very sensitive as well as the connections to the gas valves. Check the wires and make sure they are snug and tight. With it being only 2 months old, I doubt the board is bad or the flame sensor(unless it is a used system). So I would just snug and wiggle the wires on the board and the gas valve and try that.
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.