Dometic Thermostat

Chippendale said:

I am down by Corpus Christi, and last night almost froze to death, no electricity and dead batteries and then about noon today power is turned back on and the heater started right up. Only problem is the thermostat is set at 75 degrees, it won't change up or down nor can you cut it off. But it is recycling on and off about every 4.5 to 5 minutes. I called a mobile repair guy and he had me remove the unit from the wall and remove the phone jack plug for a couple of minutes and put it back. No improvement, but in trying to get something to happen it showed an E1 error code which the book says "is a loss of communication between the CCC 2 Dometic thermostat and an individual system power module board". It doesn't say if the problem is in the thermostat or the module board. I only have one zone for this thermostat so it is Zone 1. The repair guy said he would get two white thermostats, one for AC and one for Heat which doesn't excite me. In looking at Amazon, I find they have what looks like the same thing. Has anyone had a similar problem and plugged the phone jack into a new thermostat and it worked? Also, does anyone know if there is a way to clear the error code? A friend said that if you could do that it might work. Thanks for any suggestions.

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George, an E1 code is often a bad/dirty/corroded connection at the air condition - on top of the rig. It's pretty rare to have a bad thermostat.

danemayer said:

George, an E1 code is often a bad/dirty/corroded connection at the air condition - on top of the rig. It's pretty rare to have a bad thermostat.

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Dan, this thermostat is handling both the AC and Heat, and I think the problem right now might be with the "heat mode", but I guess the problem could be with either unit. Should I suggest he check the heater first and if it is OK then the AC on the roof. And if that doesn't work, I guess I can try and get a new thermostat. Thanks, George

George - I know you're without heat right now and this is the only reason I would say this...

You can wire the furnace out of the thermostat / AC circuit and get the furnace going but it's a bit involved and something you may want a pal to come over to do it.

There are two wires at the furnace that when shorted together, makes the furnace run. This circuit closure is performed by a control board up in that one AC unit.

Look at the image below. The Blue and the Blue-White wires are coming from the furnace. When those two wires are removed from the wires they're hooked to now, and then shorted together (the blue and blue-white), the furnace will run.

In fact, if you wanted to go out and buy (in-stock product link to a Walmart near you) a battery powered (double A batteries) household thermostat, these 2 wires connect to the relay of the thermostat. In this manner, you'd have a thermostat dedicated to just the furnace. I did this in a previous coach when I lost the entire AC and its control board - the one that controlled my furnace. I had no heat as the AC control board could not tell the furnace to turn on.

Here again, this mod isn't for everyone as it's electrical and involved. Just tossing it out there if you get desperate and/or want other options. Wish I was there to help you in person.

Chippendale said:

Dan, this thermostat is handling both the AC and Heat, and I think the problem right now might be with the "heat mode", but I guess the problem could be with either unit. Should I suggest he check the heater first and if it is OK then the AC on the roof. And if that doesn't work, I guess I can try and get a new thermostat. Thanks, George

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George,

If you have the Whisper Quiet type air conditioner, the thermostat talks to the A/C control board on the roof. The older style A/C has a control box inside, just above the air return. The lack of communication is preventing the furnace control board from getting power. So I don't know that checking the furnace will be helpful.

While it could be the thermostat, based on reading posts here for 10 years, I'd say the likelihood is pretty low compared to having a bad connection between the thermostat and control board. Occam's Razor applied to this would say check the A/C control board first.

But actually, even though the symptoms don't really match well, you should check the 12V DC fuse box and make sure you have a good fuse. If your rig's fuse box has LED lights that illuminate when a fuse is blown, keep in mind that the LED only lights up when there's a load; i.e. the system is switched on.

jbeletti said:

George - I know you're without heat right now and this is the only reason I would say this...

You can wire the furnace out of the thermostat / AC circuit and get the furnace going but it's a bit involved and something you may want a pal to come over to do it.

There are two wires at the furnace that when shorted together, makes the furnace run. This circuit closure is performed by a control board up in that one AC unit.

Look at the image below. The Blue and the Blue-White wires are coming from the furnace. When those two wires are removed from the wires they're hooked to now, and then shorted together (the blue and blue-white), the furnace will run.

In fact, if you wanted to go out and buy (in-stock product link to a Walmart near you) a battery powered (double A batteries) household thermostat, these 2 wires connect to the relay of the thermostat. In this manner, you'd have a thermostat dedicated to just the furnace. I did this in a previous coach when I lost the entire AC and its control board - the one that controlled my furnace. I had no heat as the AC control board could not tell the furnace to turn on.

Here again, this mod isn't for everyone as it's electrical and involved. Just tossing it out there if you get desperate and/or want other options. Wish I was there to help you in person.

Click to expand...

Jim, I guess I didn't make myself clear. From about 7:30 AM Monday till about noon today we were without electricity and running the heater kept me warm until about dark when the batteries drained out. A friend loaned me a generator and I hooked a small electric heater to it and made it through the night. My problem is when I turned on the heat at noon today to warm the trailer, the thermostat was set at 75 degrees and would not go down to 70. Then I tried to cut it off and I could not get it to cut off nor would it change modes to Cool. I was like it was locked. It would recycle every 4.5 to 5 minutes, but it was stuck on 75 and blowing hot air. You know how it is in Texas, Feast or Famine. I called an RV repair guy and he suggested over the phone replacing my Dometic with two manual thermostats, one for the heat and one for the AC. If it gets too hot, I can turn off the heat by manually removing the telephone jack like plug from the rear of the thermostat and then put it back in when I want it on. I am comfortable now, I have my fireplace on and a small electric heater. I just wanted to know if I purchase another thermostat and plugged the phone jack into it would it work. Dan suggested it might be a corroded connection at the air conditioner on the roof. I guess since I don't want the two individual thermostats, I may need to purchase a new one and if it doesn't work have the RV repair guy check the AC on the roof. If that fixes it and the old one then works, I can send the new one back to Amazon or wherever. Thanks for your suggestion about jump starting the furnace, but that is way over my pay grade. George

danemayer said:

George,

If you have the Whisper Quiet type air conditioner, the thermostat talks to the A/C control board on the roof. The older style A/C has a control box inside, just above the air return. The lack of communication is preventing the furnace control board from getting power. So I don't know that checking the furnace will be helpful.

While it could be the thermostat, based on reading posts here for 10 years, I'd say the likelihood is pretty low compared to having a bad connection between the thermostat and control board. Occam's Razor applied to this would say check the A/C control board first.

But actually, even though the symptoms don't really match well, you should check the 12V DC fuse box and make sure you have a good fuse. If your rig's fuse box has LED lights that illuminate when a fuse is blown, keep in mind that the LED only lights up when there's a load; i.e. the system is switched on.

Click to expand...

Dan, I don't know if I have the Whisper Quiet AC or not. My Grand Canyon is a 2015 and was built in early April of 2014, so I guess the AC's are whatever they put on the roof at that time. As for the fuses, I checked them and I couldn't see anything wrong. I will get the RV repair guy to check them in the morning too. Thanks for your input, I now have an idea of what I am going to do since I don't want the two manual thermostats he suggested. George

I purchased an RV thermostat from Dometic when the factory one in my RV started going out. It replaced my old one perfectly and has been functioning very well for a month now. I love that this thermostat connects to both the air conditioner and the furnace. As you probably know, some models only link to the furnace, which isn’t ideal for someone like me who values convenience.

Hi everyone,

I have been reading through all of these posts and wanted to chime in.

In a couple of words, the new Dometic T-Stat/AC controllers are JUNK. I just purchased a 2011 Sundance CLT that had the older analog system replaced with the new “Digital” system. The T-Stat capacitive buttons stopped working….actually had to take the faceplate off and touch the metal posts in order to make any adjustments.

This new system is all-digital. The 3 wires are +12V, -12V and Communication. The T-Stat sends digital pulses to the controller that is installed in the AC return air chamber….There is no longer R, RC, W, G, Y, B wiring. This makes this system completely proprietary, with no option to use a battery operated household thermostat.

Hopefully there will still be enough wires installed between the AC controller and T-Stat. If there are, there is one set of YouTube videos that shows the conversion of the Dometic proprietary controller to a Coleman Mach system controller (8330-752) This Coleman system goes back to the old multi-wire configuration, and allows for use of household battery powered T-Stat.

YouTube video:

I do not have access to a Coleman Mach controller so I was able to improvise using 2 automotive 12V relays and a non-programmable Honeywell T-Stat (RTH111B). Total cost of approximately $50CAD.

New Dometic T-Stat locally: $120CAD.
“Used” Dometic Analog control kit locally: $250CAD
New Coleman 8330-752 controller Amazon: $115CAD.

Limitations of my setup:
1. I only used 2 relays (one for AC and one for FAN HI) so no ability to use AC FAN LO.
2. No connection of Freeze sensor to cut out AC in event of freeze up. (This logic would be from the Control Board).

Here is another replacement option that has good reviews

Treysmith9 said:

How hard would it be to switch from Dometic 3316250.012 to a Dometic 3314082000? I have a 2018 Heartland Big Country and the absolute hate the most is the thermostats in this thing. I have 2 A/C and they have their own thermostats. One in the master and the other for the living room and big furnace. The thermostats that are installed have three wires going in it, while the other has a plug in that looks like a phone plug in.

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I have a Dometic 3314082.000 in the bedroom of our 2012 Heartland Big Country 3595RE. We have a Dometic 3316155.000 in the living area. I hate the one in the bedroom, it does what it wants to and requires a book to set it. Each thermostat controls one AC unit (Without heating in it). Have you changed out your thermostats? If so what did you install and how did it go? I want a simpler thermostat in the bedroom, without zones and programs on it.

During winter, set the temperature to 5 degrees higher than the temperature outside. Conversely, set the thermostat to 5 degrees lower than the outside temperature when it’s summertime. These adjustments should help keep your RV at the most efficient temperature.