Hot A/c wall thermostat

The friendliest place on the web for anyone with an RV or an interest in RVing!
If you have answers, please help by responding to the unanswered posts.
See posts with no answers
Art In Mobile

Art In Mobile

Well-known member
Joined
Jan 5, 2009
Posts
372
True Air Coleman-Mach thermostat has always read about 7 degrees hotter than the room temp. I put my hand on the cover & where the big word (Air) is, it is warm. Warm enough to make the sensor read high as it is high inside that cover. I removed the cover & with an IR no contact thermometer found the 2 capacitors at the 3 o'clock position reading 104 degrees. There is just no way for that heat to disperse with that cover on so it radiates to the temp sensor reading hot all the time. This is without the heat or A/C on. Anyone else had this problem?  Battery voltage is where it should be so not over powering the thing. Sure wish the temp sensor was well away from the heat source. Art
 
Could be "dirty" 12 vdc.  Excessive ripple on the DC could cause overheating of electrolytic capacitors.  First, measure the 12 vdc at the thermostat and make sure it is in the ballpark - not over about 13.6 vdc.  Then, assuming you have a good well charged battery, try on battery power only (not plugged in).  If they run cooler, your convertor might be faulty.  That said, some convertors don't provide very clean DC if the house battery is not good.  The battery provides filtering.  And then that said, it could be the capacitors if an excessively high voltage has been applied for any length of time.
 
Molaker, thanks for the reply. Volts are 11.17 at the thermostat, with the small gauge wire & long run seems about right. Two new battery's installed  to absorb shaky DC voltage from converter. I think if they had the temp sensor away from the electronics this would help as most 12 volt mother boards produce some heat. You could be right about the caps having a problem. Thanks Art
 
You might trace the 12V wires from the panel and install a filter capacitor across them in a location well away from the caps.

Ernie
 
Art In Mobile said:
Molaker, thanks for the reply. Volts are 11.17 at the thermostat, with the small gauge wire & long run seems about right. Two new battery's installed  to absorb shaky DC voltage from converter. I think if they had the temp sensor away from the electronics this would help as most 12 volt mother boards produce some heat. You could be right about the caps having a problem. Thanks Art
Click to expand...

That voltage is way too low. Can you measre the current going to thermostat?
 
John Hilly, thanks also for your reply. I will try to measure the current later but the thing seems to get hot when even the A/c or heat is not on. As you have the same basic system next time you are in your unit could you please put your finger on the two caps at the 3 o-clock position & see if they are slightly warm. I notice with the cover off the room temperature on the display seems about right. That cover seems to keep in just enough heat to be a nuisance. Thanks Art
 
John, thanks for the (not even warm reply) as mine must have a problem.
  catblaster, thanks for your reply & I have worked with anticipator's before but the heat is positively coming from the caps. I will do some more investigating. Thanks for all the suggestions Art
 
I'm not sure the Coleman t-stat would have a heat anticipator, but I don't have that one in my current coach. My Atwood Comfort Control doesn't have one, though, and I think that is common in digital thermostats. Perhaps because they react quickly to temp changes and don't need to anticipate? That's just a guess...
 
Gary RV Roamer said:
I'm not sure the Coleman t-stat would have a heat anticipator, ..
Click to expand...
I don't think it does either, I'm pretty certain anticipators are only present in mechanical t-stats.  Art - why not replace the Coleman-Mach t-stat for a programmable one?  We are totally happy campers with our Ecobee but you could get by with a less fancy programmable Honeywell model.
 
You must log in or register to reply here.

Latest posts

Members online

Total: 891 (members: 37, guests: 854)

Forum statistics

Threads
131,917
Posts
1,387,446
Members
137,672
Latest member
Davestic
Back
Top Bottom