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-   -   installing new t-stat (http://www.forestriverforums.com/forums/f16/installing-new-t-stat-54931.html)

ramair 02-20-2014 03:12 PM

installing new t-stat
 
ok guys need some help here, I am wanting to change out our t-stat in our bedroom to a programmable one. having issues with the dometic one but looking at the stock one it only has 3 wires. When I changed the one in our 5th wheel it was 5 wires, need assistance as to which programmable t-stat will work and the wiring for the 3 wire. Thanks in advance I have a 2012 378XL with dometic ac and surburban heaters, no heat strips or heat pumps.

alparmer 02-20-2014 03:46 PM

I've been wanting to install nicer stats on ours too, but haven't gotten around to removing them to see how many wires are behind them. Three wires seems odd. Not sure how they work, but I would think two for power, one for AC/compressor signal, one for heater signal, and one for fan. Like I said, I really don't know how they work so I'm assuming here.

ramair 02-20-2014 04:00 PM

there is a red=12v+, white=12v- and a orange= common. That is what is throwing me off. talked to someone and there is a circuit board in the ac unit which controls other things. all the programmable t-stats I have seen work off of 4-5 wires.

canmannc 02-20-2014 04:11 PM

T stat wiring
 
Quote:

Originally Posted by ramair (Post 546126)
there is a red=12v+, white=12v- and a orange= common. That is what is throwing me off. talked to someone and there is a circuit board in the ac unit which controls other things. all the programmable t-stats I have seen work off of 4-5 wires.

ramair, Just got mine working. Installed a Honeywell RTHL111. Not programmable but the other programmable Honeywell should wire up the same. I removed my Duotherm T-stat and the new one wires as follows:
Camper=Honeywell T-stat
Red = not used (tape it off-the Honeywell uses 2 AAA batteries)
Green = RcRh Jumper together
White = White (furnace-Heat)
Yellow = Yellow (AC Cool)
Orange and Blue = G terminal (Fan)

Note: Wiring this way you will only be able to use "Hi" fan...no low fan setting

Hope this helps! Good Luck!!

ramair 02-20-2014 04:19 PM

canmannc, thanks for the info but I only have 3 wires, according to your diagram you have a 5 wire setup, if I did not use the red then I would only have 2 wires used. That's the confusion part. I did my 5th wheel when I owned it and you setup is correct for that. Thanks

David 01 02-20-2014 05:57 PM

Great question, as a seasonal camper, I would like to replace my thermostat with a programmable model to set my thermostat to turn on the A/C about 1 hour before I arrive every Friday afternoon to get things cool. I saw some of these mods on another forum and there were so many jumpers and extra switches added I just said Forget about it! I don't think it should be that complicated. Actually you would think Dometic would sell one as an aftermarket replacement or upgrade.

awwall 02-20-2014 06:13 PM

Folks, it can't be done. The Dometic uses a communication bus to talk to the main board located at A/C unit. From there it controls the A/C, Fans, Heat, and heater strips if you have them. Unless you change out both the control board and thermostat, it can not be changed. Believe me, I have researched this thoroughly. I keep hoping that Dometic comes out with a programmable. :crying:

ramair 02-20-2014 10:08 PM

awwall, thanks for the information I was afraid of that, well least we all know the answer, to that question.

cjd10 02-21-2014 06:05 AM

Quote:

Originally Posted by awwall (Post 546187)
Folks, it can't be done. The Dometic uses a communication bus to talk to the main board located at A/C unit. From there it controls the A/C, Fans, Heat, and heater strips if you have them. Unless you change out both the control board and thermostat, it can not be changed. Believe me, I have researched this thoroughly. I keep hoping that Dometic comes out with a programmable. :crying:

I wonder if this is the reason the AC unit in my bedroom does not blow as hard or loud as the one in the front. They are both 13.5's but the one in the rear is just not as powerful. Works fine in the smaller area though, actually is usually cooler than the one up front. A circuit board controlling fan speeds would explain this.

alparmer 02-21-2014 07:29 AM

Quote:

Originally Posted by awwall (Post 546187)
Folks, it can't be done. The Dometic uses a communication bus to talk to the main board located at A/C unit. From there it controls the A/C, Fans, Heat, and heater strips if you have them. Unless you change out both the control board and thermostat, it can not be changed. Believe me, I have researched this thoroughly. I keep hoping that Dometic comes out with a programmable. :crying:

That's what I was afraid of. I guess it would make sense to only have three wires. Two to power the stat and one for communication. I wonder why Dometic hasn't come up with a programmable unit. Wouldn't take much.


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