installing new t-stat

[ramair]

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]

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]

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]

Originally Posted by ramair

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]

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]

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]

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.

[ramair]

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

[cjd10]

Originally Posted by awwall

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.

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]

Originally Posted by awwall

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.

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.

[Krazymace]

My rig has a thermostat in the bedroom, which is where the AC unit is located. Problem is, they are too close together. Bedroom quickly cools down and AC shuts off. Can only run the front AC on a more continuous basis. Wish FR would have put both thermostats in the same location to even out the workload of the two units. I have no idea how to relocate it.

[Iwannacamp]

how bout this...

http://www.primetimerv.com/download/...structions.pdf

or search GOOGLE Dometic programmable

[ramair]

Well I just found out that you can reset the the t-stat, which resets the computer board in the ac unit. Turn the tstat off once off push and hold the mode and + at the same time for approx 4/5 seconds and - -(dash dash) will appear. That will reset everything. Then you can turn it back on. Problem I was having was the furnace was not turning on but if you turned it off and then back on it would work fine. I think this solved my issue.

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[alparmer]

Originally Posted by ramair

Well I just found out that you can reset the the t-stat, which resets the computer board in the ac unit. Turn the tstat off once off push and hold the mode and + at the same time for approx 4/5 seconds and - -(dash dash) will appear. That will reset everything. Then you can turn it back on. Problem I was having was the furnace was not turning on but if you turned it off and then back on it would work fine. I think this solved my issue.

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That's good to know. BTW, I sent an email to Dometic asking if our units can be upgraded to the programmable Tstat. We'll see what they say.

[cjd10]

Originally Posted by Iwannacamp

how bout this...

http://www.primetimerv.com/download/...structions.pdf

or search GOOGLE Dometic programmable

Camping World shows those on sale for $108. They should know if it would replace the stock ones

[awwall]

Originally Posted by alparmmer

That's good to know. BTW, I sent an email to Dometic asking if our units can be upgraded to the programmable Tstat. We'll see what they say.

I thought I could do something with their 4 zone programmable, but it also is different. The use a special Cat5 interface and totally different control board.

I am anxious to see what they tell you....

[David 01]

here is my response from Dometic received today...

" Unfortunately at this time we don't have a t-stat that would replace the single zone and be programmable short of doing some rewiring in the wall. You are correct the multi zone system can be programmed and be set up for the way you would use it. Although it would require rewiring. Thank you and have a Great Day!!! "

So it can be done in a single zone system, but only if you are willing to rewire the whole thing. That sounds like a PIA to me, so I will just forget about it....for now....

[Iggy]

Originally Posted by ramair

Well I just found out that you can reset the the t-stat, which resets the computer board in the ac unit. Turn the tstat off once off push and hold the mode and + at the same time for approx 4/5 seconds and - -(dash dash) will appear. That will reset everything. Then you can turn it back on. Problem I was having was the furnace was not turning on but if you turned it off and then back on it would work fine. I think this solved my issue.

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Lots of information in the thread.
ramir what actually does this do when you reset the AC units computer board?
Thanks

[ramair]

Iggy

If your having issue with one off your units like I was resetting clears any memory and restores factory defaults. Hope this helps clear things up

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