Furnace Thermostat issue - I think

[Boozecamp]

My furnace works fine, but here recently, it only kicks on if you move the digital read out up beyond room temperature, then it kicks on. For example, if you set the thermostat to say......62 and the inside temp falls below 62, even if it gets down to low 50's or 40's inside (overnight), it will not kick on. But if I manually raise the thermostat temp up a few degrees, it will kick on. I assume its a faulty thermostat!?!?!
Has anyone experienced this? Any suggestions? If I need to replace it, I'd like to get a programmable one from wally world or other big box hardware store.

 

[danemayer]

I'm assuming you have the Single Zone LCD thermostat shown below. At one of those times when the furnace doesn't start, cycle the thermostat to OFF and press the + or - key to see what temperature the thermostat is reading. Ours reads accurately, but the temp in the hallway is usually at least 5 degrees higher than at the rear of the coach.

If you have a heat source in the basement, the hot air rising behind the wall could be causing the thermostat to think the interior temp is higher than it actually is.

Also, to start the furnace, are you ONLY raising the set point temp, or are you recycling the mode OFF and back ON? If you're recycling, you might be clearing a lockout condition caused by another failure.

 

[Boozecamp]

I'm assuming you have the Single Zone LCD thermostat shown below. At one of those times when the furnace doesn't start, cycle the thermostat to OFF and press the + or - key to see what temperature the thermostat is reading. Ours reads accurately, but the temp in the hallway is usually at least 5 degrees higher than at the rear of the coach.

If you have a heat source in the basement, the hot air rising behind the wall could be causing the thermostat to think the interior temp is higher than it actually is.

Also, to start the furnace, are you ONLY raising the set point temp, or are you recycling the mode OFF and back ON? If you're recycling, you might be clearing a lockout condition caused by another failure.

Yes, that is my thermostat. I don't cycle the thermostat with on/off mode. But I did remove the duct from the bedroom floor vent and left it in the basement area behind the removable wall where all the utilities are so it would add more heat to the belly to prevent freezing. Is it potable that is causing my problem? I didn't want to plug the duct as it might creat a back pressure issue for the sail switch. The heat sensor for thermostat is not in the wall. I might just have temp differential issue. I will try your suggestion on the thermostat.

 

[danemayer]

Yes, that is my thermostat. I don't cycle the thermostat with on/off mode. But I did remove the duct from the bedroom floor vent and left it in the basement area behind the removable wall where all the utilities are so it would add more heat to the belly to prevent freezing. Is it potable that is causing my problem? I didn't want to plug the duct as it might creat a back pressure issue for the sail switch. The heat sensor for thermostat is not in the wall. I might just have temp differential issue. I will try your suggestion on the thermostat.

Yes, it's possible that the heat from the bedroom duct is rising behind the thermostat, confusing it. You can tell by cycling the thermostat to OFF and pressing the + or - key to see what temperature it thinks the room is at.

 

[Boozecamp]

Yes, it's possible that the heat from the bedroom duct is rising behind the thermostat, confusing it. You can tell by cycling the thermostat to OFF and pressing the + or - key to see what temperature it thinks the room is at.

You nailed it! I Checked temp at thermostat and it registered 70. However, the actual temp in living area on the couch is 65. So the thermostat was not coming on until it was very chilly. so to test it, I sat the thermostat to 69 and when thermostat temp read 68, it fired up. Thanks. Now I just need to set the thermostat about 5 deg hotter so it will be in sync with our temp in living.

 

[rxbristol]

If you have a heat source in the basement, the hot air rising behind the wall could be causing the thermostat to think the interior temp is higher than it actually is.

Awesome troubleshooting, Dan.

 

[whp4262]

Good job danemayer

I'm usually pretty good at troubleshooting but I think I probably would have missed that one.


Sent from my iPhone using Tapatalk

 

[simsfmly]

Did not know you could "read its mind" by turning off then toggling the + / -. Nice tip, Dan.