Coleman Mach basement heat pump problem

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JoelP

Well-known member
Joined
Nov 2, 2016
Posts
704
Location
San Jose, CA
My Coleman Mach Model 7535D871 basement heat pump furnace combo just stopped providing heat on a very cold night in Elko,NV. This will not heat on electric or propane. The thermostat calls for heat and a blower turns on. For propane the burner fires up. In both cases after 2-3 minutes it shuts down entirely.

When it starts up the green LED on the control PWB flashes its normal pattern. When it shuts down the same pattern continues, saying that the logic doesn?t detect an error. It behaves as though the 2nd stage is not firing up.

I would love to get my hands on a shop manual, but maybe one of the experts on this forum has experienced this kind of issue. My guess is that a relay may have failed on the PWB, but one would think this would produce an error code. Any idea where I can order a replacement PWB?

Any input on this would be appreciated.






 

Wizard46

Well-known member
Joined
Mar 12, 2009
Posts
2,093
Not sure about your particular model number but most the electric and propane heat it two separate units although the same thermostat controls both. The heat pump will not work below about 40 degrees. Would need to know the model of the furnace to talk about it. Could not find that Coleman model number
 

JoelP

Well-known member
Joined
Nov 2, 2016
Posts
704
Location
San Jose, CA
It seems my problem is with the furnace and not the heat pump.  They are both controlled by the same thermostat, but are separate units.  My furnace is the Suburban SHD-2542.  I think I see a shop manual on line so I will look at that and see what I can figure out.  I was told that it is possibly a high temp limit switch or another interlock to check for airflow that may be stuck.  I pulled the cover and these items didn't exactly jump out at me.
 
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