My Goodman GMPN080 furnace has been acting strangely for several years now.
After a concerted effort, I have determined that the stack over temp switch
is opening at 140 degrees F, and not closing until it gets down to about
110 degrees F. This causes the gas valve to shut off. The controller
tries three times to relight it, then shuts everything off for an hour,
with a single LED flash code on the controller card.
My question is: is this switch malfunctioning, or is 140F an unusually high
If your Goodman is acting strangely, tell it to stop.
Who all was involved in this "concerted" effort?
I checked the parts break down sheet of the GMPN080. No "stack over
temp switch" is listed. Maybe you are really just looking at your
If the gas valve is shutting off, tell it to stop that.
Id change the thermostat and wiring. That should take care of it.
Ha ha! You guys crack me up. It's nice to see that you extremely
experienced HVAC professionals still know how to have fun.
The concerted effort I mentioned was performed by me, myself and I.
For those of you who have never heard of a stack over temp switch, there
is one on this list of Gas Furnace Repair Parts from Goodman
Manufacturing Company. Check out Item 19.
There are a few of them for sale on this page:
This one is mine:
If there is anything else you extremely experienced HVAC professionals
would like to learn from a total clueless fucking amateur, let me know.
By the way, my fridge did have the same problem, but I slapped that
bitch upside the icemaker and it came around. The furnace don't respond
Your best friend,
Did your buddies at "Arnolds" have any other advice for you regarding the
potential hazards of the Goodman??
Did you inquire as to why your "stack over temperature" switch was tripping
in the first place??
Are your life insurance premiums up to date?
That's kind of what I was asking here. What I got was a whole lot of
superior attitude and not much intelligence.
I'm not talking about jumpering out the switch or anything rash like that.
I'm going to replace it and see if it fixes the problem. I was hoping that
some experienced person would tell me whether the situation I described
You know, it's a furnace. It's a bunch of switches, valves, and sensors,
no less understandable than a computer or a car. Some of it takes
specialized knowledge and tools, but some of it is within the reach of an
intelligent logical homeowner.
I have found countless cracked heat exchangers on the Goodman GMPN furnace.
93-95 are the worst. Cracks are hard to find, almost impossible to see. Take
it out, look at the back on the formed part of the s bend in the clamshell
tube portion. It's non welded, a lock fitting. They have a 20 year warranty,
but I would buy a new furnace. Chances are its sucking air and causing stack
temp to increase. 140F is high for a high efficiency.
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Most of the guys in here get paid to answer questions like yours. You
think replacing a part will fix it? Only temporary my boy. Very
temporary. Then that one will do the same thing. The magic is not how
to replace the part..........its WHY?
After you've thrown a few parts at it, you"ll begin to grasp why it is
cheaper and easier to call someone who knows what they are doing.
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