furnace won't shut off

h2ok9

Member
Woke up this morning to a 81 degree unit. Furnace apparently came on and didn't ever shut off. Checked t-stat---set @ 68 deg. Lowered t-stat to 50 and still wouldn't shut off.
Did get it to shut down by turning unit off. Then thought maybe t-stat bad so switched t-stat in hall with t-stat in b/room (ac only). Furnace came on and wouldn't shut off. Then thought I'd try the heat pump. Heat pump wouldn't shut down either. Do i have a t-stat problem? or is it furnace? or heat pump? or all of the above. No prior HVAC problems. Oops---- unit is a suburban sf-42 in a 2011 rushmore w/dometic duo therm control center.
FYI--can't find any info in my packet regards air conditioners. Any help appreciated.
 

GOTTOYS

Well-known member
2011 should be under warranty. Any dealer with a qualified tech can fix it. A heating/A/C company could work on it also. Possibly a pinched wire, stuck relay or control. Don't mess with it if you aren't sure. The problem shouldn't be hard tofind if you know what to look for....Don
 

h2ok9

Member
Thanks for reply

Went home at lunch and turned furnace on for the heck of it and the dang thing worked fine--go figure--is this like the sqeaky, grinding noise thing that the DW hears on her car but won't replicate for me or shop???? Guess we will see how things work tonite.
 

caissiel

Senior Member
During our traval south the furnace fan would come on but the furnace would not put out any heat. It was caused by a low voltage problem during a cold night without electric power and the furnace killed the batteries.

After 3 days of trying the problem wet away. Its a great feeling when things fixes itself.

All that I could conclude was that the battery voltage was never high enough to reset the controls and after higher voltage with a new battery it seam to reset itself.
 

GOTTOYS

Well-known member
Now the question is do you trust it? I would still have someone look at. Having the furnace run constantly and overheating could have serious consequences...Don
 

danemayer

Well-known member
The furnace thermostat controls a relay box that is located (strangely enough) in the main A/C unit that's over the kitchen island in your Rushmore. If you drop the filter cover and filter, you'll see the square box with about 4 connectors plugged in. You might want to just see if the connectors are all seated properly.
 

hoefler

Well-known member
Since the heat pump and the furnace are two separate appliances, it has to be in the thermostat or wiring close to the stat. The thermostat is the only thing in common with the two units. Low voltage can really screw up anything electronic, that is the first place to look. Check your residual voltage with the furnace running and any light you might have on, it needs to be close to 12 volts with it running. Make sure your battery connections are wrench tight, not just hand tight.
 
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