Thermostat thinks it's 90 - actually 62 degrees

danemayer

Well-known member
The Dometic Single Zone LCD Thermostat in our 2011 Rushmore is way off on the temperature. It thinks the temp is already at 90 degrees even though it's actually 62.
Because of this, the furnace isn't keeping the basement very warm.

Earlier today, it seemed to be off by about 15 degrees (75 vs 60). Now it's off by 28 (90 vs 62).

I checked the manual, but I don't see any way to deal with this. The manual shows how to display the current temp (as opposed to the desired temp) and I confirmed it thinks the interior temp is 90.

Anyone have any experience with this? Any ideas?
 

Willym

Well-known member
I don't have one of these, (my 2011 came with an analog unit) but I did a search and found an operating manual (OM). Has the unit been initialized per the OM? Another search found a query regarding operation of a DIP switch in the unit. I'm not sure if your unit has a DIP switch, but you could look and try changing it's position if it has one.
 

hoefler

Well-known member
There is a temperature differential adjustment it it, it could be out of whack. Another thing to check, make sure the rig is level side to side and front to rear, place a small level on the thermostat and make sure it is level to the rig.
 

Rickhansen

Well-known member
The differential setting mentioned previously is to adjust the cycle rate, not for sensor calibration. Do not adjust this in attempt to calibrate your device. I'd suggest that you are getting warm air from the furnace blowing onto the thermostat, or duct leakage blowing warm air through the wall that the thermostat is mounted on. Remove the thermostat and mounting plate and seal the hole that the wiring penetrates the wall. Direct any nearby vents as far away from the thermostat as possible.

Your thermostat is a digital model, and is not affected by leveling of your rig or mounting.

If the problem is indeed calibration, replace the thermostat. I'd recommend a Hunter digital T-stat from Wal-Mart. Wiring details can be found on this forum with a simple search.
 

danemayer

Well-known member
The thermostat thinks it's 84 even with the furnace off for hours and the inside temp in the 50s, so I think it's the thermostat.
Heartland Customer Service helped coordinate with Dometic and a new thermostat and relay box will arrive tomorrow.
 

Rickhansen

Well-known member
Danemayer,
That's seems to be good diagnosis and resolution. I had recommended an "off the shelf" programmable because they are cheap and work well.
I had, and didn't like, the Dometic T-stat as it was not programmable and was difficult to operate. I replace both of our thermostats with Hunters so that they operated consistently, and I could program them based on our occupancy. I also could set them up to lead-lag based on time of day, so that the noise and airflow was in the desired area.
 

Tom of Ypsi

Well-known member
Just had the same thing happen Solution: Pull the furnace fuse, 20A, and wait for a couple of minutes, reinsert fuse and problem was solved. Seems like the brain needs to be reset. This my second time with the last time being a coouple of years ago.
 

danemayer

Well-known member
Pulling the fuse for 20 minutes didn't help. New thermostat from Dometic did the trick. Also taped over the rather large hole in the wall behind the thermostat to make sure no heat from below was influencing the thermostat. Furnace is operating correctly now.

Btw, I'm surprised to find that 2 other digital thermometers that I have both disagree with the Dometic and with each other. Variance is only a couple of degrees, but now I don't trust any of them to be accurate.
 

Ray LeTourneau

Senior Member - Past Moderator
Btw, I'm surprised to find that 2 other digital thermometers that I have both disagree with the Dometic and with each other. Variance is only a couple of degrees, but now I don't trust any of them to be accurate.
We have 2 thermometers and 2 t'stats. None of them agree on the temperature. Probably cause it might be a couple degrees difference in the different areas of the rig.
 
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