Comfort Control Thermostat - how does it work??

[Darryl]

My '97 Endeavor has the 4 button Dometic Comfort Control thermostat system, with two A/C units on the roof. I'm trying to figure out the logic of this thermostat. If you set the front & rear unit to the same degree setting, the rear will kick of several degrees before the front does. I can understand this happening, if they had different "thermisters" (one in the back and one in the front), but they don't. There is no sensing unit in the rear and the best I can tell, only one in the front (inside the thermostat). At least, if there is one in the back, it must have the Klingon cloaking device around it ---- I can't find one anywhere.

So this leaves me with one conclusion. There must be logic in the control that turns off the rear unit X degrees before the front. Both A/C's are plumbed into the same distribution ducting. Air comes out into the motorhome front-to-rear when either are on. Adding the second unit only increases the volume. By the way, I installed a new Comfort Control thermostat this week and it does the same thing as the orginal.

If anyone has any knowledge of how these work, your reply would be most appreciated.

[Darryl]

My '97 Endeavor has the 4 button Dometic Comfort Control thermostat system, with two A/C units on the roof. I'm trying to figure out the logic of this thermostat. If you set the front & rear unit to the same degree setting, the rear will kick of several degrees before the front does. I can understand this happening, if they had different "thermisters" (one in the back and one in the front), but they don't. There is no sensing unit in the rear and the best I can tell, only one in the front (inside the thermostat). At least, if there is one in the back, it must have the Klingon cloaking device around it ---- I can't find one anywhere.

So this leaves me with one conclusion. There must be logic in the control that turns off the rear unit X degrees before the front. Both A/C's are plumbed into the same distribution ducting. Air comes out into the motorhome front-to-rear when either are on. Adding the second unit only increases the volume. By the way, I installed a new Comfort Control thermostat this week and it does the same thing as the orginal.

If anyone has any knowledge of how these work, your reply would be most appreciated.

[RV Wizard]

Darryl, there are two thermistors used on the two zone setups. One is in the t'stat and one is located in the zone two area. It can be on the underside of a cabinet, on a wall or may even be near or in the return air. I suspect that you have a vent directing airflow directly onto the zone two thermistor to cause it to cycle the unit off sooner. Call Monaco and ask for tech support to reveal location if you don't find it.

[Darryl]

Thanks Mike for the reply. I have hunted everywhere for that rear thermister and can't find it anywhere! H.R. really hide this one. Unless it's in the intake of the A/C, I can't imagine where it is. (The guy that hide these must be the same guy that hide the Easter Eggs when I was a kid ----- I never could find the darn things!!!) Tomorrow I will call H.R.

[footdoc]

Mike...on my coach, I just found a second thermistor...there is one in the bedroom and I assumed the other was up front over the windshield in the tstat body...a bad/hot place to be...My one for the front zone was just found under a kitchen cabinet...a much more logical place for it

[Glen M]

I have the same ac type of unit. I have a rear temperature sensor – it is not a thermostat. Mine looks like a plastic vent that is about the size of a silver dollar. I removed the cover and it is just a resistor (or some electrical component that senses the temperature). Mine is on the side of a cabinet by the head of the bed (all the way in the rear of the RV). I hope this helps.

[Darryl]

Guys, I found it. It was located inside the air intake for the rear A/C. It resembles a telephone cord, about 10 feet long, with a heat sensor at the end. Very thin/small sensor with heat shrink around it, except for the tip.

I'd really like to put it in a remote area, out of the air intake, but that isn't really possible without running the wire across the ceiling. Probably the next best thing would to be to mount it on the bottom side of the A/C panel, at the opposite end of the air intake. This would get it out into the ambient air more. Does anyone know if they make a surface mount "holder" for the sensor?

[teddyu]

The attachment can be anything of your choosing. Do not place the sensor (tip) in contact with anything - allow air to freely circulate around the tip. The clamping/mounting device should not crush the wiring. Do not bend anything under the shrink tubing. Drilling a small hole in a panel and slipping the tip through the opening should suffice for that sensor if you wish to hide it.