# Goodman furnace "open high limit"



## frenchelectrican (Mar 15, 2007)

If that main fan motor do have PSC ( perament split circuit ) one of the winding is getting weak it may cause hard starting on that. that is more noticeable on unit with very high running hours .,,

but some case you may have DC blower motor in there.,, if that is the case maybe a brush or brushless motor but somewhere along the line when ya turn it by hand it may reset where you dont have weak spot on the DC motor in there.


Check the return air filter to make sure it is not clogged up that is most common curpit for causing high limit to trip out.


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## Switched (Dec 23, 2012)

frenchelectrican said:


> If that main fan motor do have PSC ( perament split circuit ) one of the winding is getting weak it may cause hard starting on that. that is more noticeable on unit with very high running hours .,,
> 
> but some case you may have DC blower motor in there.,, if that is the case maybe a brush or brushless motor but somewhere along the line when ya turn it by hand it may reset where you dont have weak spot on the DC motor in there.
> 
> ...


This is also the cause to most capacitor failures on central AC units.


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## MechanicalDVR (Dec 29, 2007)

As Frenchy said check the filter before anything else, lack of air flow across an air over motor will over heat it, also if there is an a/c coil on the furnace check the face of the coil for dust/crud build up from the unit running without a filter or a clogged filter collapsing and passing dirt to the coil face.

If there is a 'spill' limit stat in the same circuit check the flue to make sure there is nothing clogging it or slowing the venting process. Could be a birds nest or even ice up there by you.


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## RePhase277 (Feb 5, 2008)

After all the routine stuff, you can get deeper. We may have had the same Goodman furnace you do. Same failure. I put 120 volts straight to the fan, and it worked fine. I measured the duct temp while it worked. Fine. Checked the supposed open limit, fine. Bypassed all the limits, still went out on open high limit.... bad board. New board was several hundred bucks because the unit was obsolete. Now the unit is sitting at the scrap yard.


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## MechanicalDVR (Dec 29, 2007)

RePhase277 said:


> After all the routine stuff, you can get deeper. We may have had the same Goodman furnace you do. Same failure. I put 120 volts straight to the fan, and it worked fine. I measured the duct temp while it worked. Fine. Checked the supposed open limit, fine. Bypassed all the limits, still went out on open high limit.... bad board. New board was several hundred bucks because the unit was obsolete. Now the unit is sitting at the scrap yard.


Get an aftermarket control board in that instance they run around $35-$70 at places like United Refrigeration and Johnstone Supply.


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## PlugsAndLights (Jan 19, 2016)

It stopped working again. Blower motor was really hot so that was one more 
sign it was cooked. Changed the motor and cap. Started up and ran fine. Hope
it stays that way. 
P&L


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## Navyguy (Mar 15, 2010)

I had the same problem also; took the cover off, went through the starting sequence, etc. Finally realized that when the cover was off and the switch bypassed, there was tons of air across the motor which kept it cool to run indefinitely. Once I put it all back together it would fail.

Scratched my head on that for quite awhile! Glad you figured it out faster then I did!

Cheers
John


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## RePhase277 (Feb 5, 2008)

MechanicalDVR said:


> Get an aftermarket control board in that instance they run around $35-$70 at places like United Refrigeration and Johnstone Supply.


Those jokers dont sell to anyone without a state HVAC license around here. I found a board online, but that system was on his last leg in other places too. It had to go. I only use the A/C now. Wood heats the place in the winter.


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## MechanicalDVR (Dec 29, 2007)

RePhase277 said:


> Those jokers dont sell to anyone without a state HVAC license around here. I found a board online, but that system was on his last leg in other places too. It had to go. I only use the A/C now. Wood heats the place in the winter.


I had a license for HVAC/R and a Freon Certification.


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