Want To Replace My HVAC Thermostat

[ManWonder]

I have a Honeywell digital thermostat that I want to use in place of my Dometic analog one in my 2004 Roadtrek 190 Popular. Has anyone on the forum done this? I have replaced several in my homes but in this case I am unsure about the wiring. The new thermostat has a setting for emergency heat which I hope to use for the heat pump heat my RV has. Also, I am aware I will need another switch for the 2-speed fan setting though for now using the low setting only is fine for me. Any help would be appreciated.

[markopolo]

I've done similar to that. You should be able to find Dometic to Honeywell wiring guide on a forum. Look for Dometic to Supco wiring if you can't find it for Honeywell. Mine was Coleman to Supco.

The positives of this mod:
1. Low cost
2. Precise temperature control
3. Digital temperature display

The negatives of this mod:
1. The Freeze Protection feature typically found in household type thermostats will use up your propane supply quickly in Fall & Winter. Remove thermostat from wall plate and remove thermostat batteries in the off season to avoid that.
2. Those type of thermostats require batteries (AA or AAA) for power.

The positives outweighed the negatives for me as I was replacing a failed thermostat.

[hbn7hj]

The Cool Cat of 2004 uses an analog thermostat with 13 (guess) wires. I have heard of a person replacing the old control board in the Cool Cat with a new one (2013+?) that uses the Dometic digital three wire thermostat. Trying this will require removing the A/C from the roof. We could never get more info on this mod 'cause the owner didn't do it, a service shop did. First you would have to acquire the new control board and thermostat. Maybe Dometic would tell you if it is possible.

Myself, I replaced a 2003 Cool Cat with the digital model in 2015 which has the digital thermostat with 1 degree hysterisis. The one thing you can do is take the two green furnace wires and tie them to a digital thermostat. The analog thermostat runs the A/C and the digital runs the furnace. The digital thermostat is a great improvement.

I don't know of a cheap way to digitally control a Cool Cat A/C unit. I paid $1100 for a new one. Should you be successful with the control board route we all want to hear about it.
Harry 2003 C190P Roadtrek

[peteco]

Originally Posted by hbn7hj

The Cool Cat of 2004 uses an analog thermostat with 13 (guess) wires. I have heard of a person replacing the old control board in the Cool Cat with a new one (2013+?) that uses the Dometic digital three wire thermostat. Trying this will require removing the A/C from the roof. We could never get more info on this mod 'cause the owner didn't do it, a service shop did. First you would have to acquire the new control board and thermostat. Maybe Dometic would tell you if it is possible.

Myself, I replaced a 2003 Cool Cat with the digital model in 2015 which has the digital thermostat with 1 degree hysterisis. The one thing you can do is take the two green furnace wires and tie them to a digital thermostat. The analog thermostat runs the A/C and the digital runs the furnace. The digital thermostat is a great improvement.

I don't know of a cheap way to digitally control a Cool Cat A/C unit. I paid $1100 for a new one. Should you be successful with the control board route we all want to hear about it.
Harry 2003 C190P Roadtrek

Harry,
What failed on your original CoolCat? Where did you get the new CoolCat? Mine acts flaky at times but I think it is the reversing valve solenoid. I am not real happy about the thermostat either and would replace it for a better one if possible.
Pete
2006 RT 210P

[hbn7hj]

"What failed on your original CoolCat? Where did you get the new CoolCat? Mine acts flaky at times but I think it is the reversing valve solenoid. I am not real happy about the thermostat either and would replace it for a better one if possible.
Pete
2006 RT 210P"

Nothing failed. It was full of corrosion having lived in Florida so rather than upgrade it I replaced it.

The reversing valve solenoid can be replaced cheaply but a digital thermostat is so much better that replacing the unit is a good option. Any Dometic dealer will sell you one. I bought mine from PPL. The thermostat does not come with it. Ordering the Thermostat from PPL they sent one with a control board I couldn't use for an extra $150. The Dometic three wire thermostat is available on EBay for $50. Maybe you will get a better phone order person. You want the thermostat, not a thermostat upgrade kit which they don't make for the Cool Cat.

You can email me at hbn7hj at aol dot com if you really want to do this. You need a second person to get the unit out of the Roadtrek and on the ground.

You will take three of the original 13 wires and connect them to the new thermostat. I assume you can use solder and heat shrink.

The end result is great. The furnace kicks on before you get chilled and kicks off before you fry. Same with A/C. For me the $1100 was worth it.
Harry 2003 C190P Roadtrek

[markopolo]

Replacing the analog t stat with a Dometic branded digital one seems to be complicated and or expensive.

Maybe I'm missing something here but the t stat wiring shown staring on page 50 or so in this doc: http://bryantrv.com/docs2/docs/acservice.pdf - does not look unusual.

[hbn7hj]

All I can say is try it with the Cool Cat which is different, tho using the same analog thermostat. I purchased the Dometic digital upgrade kit for the roof mount units ($200). I can tell you it does not apply to the Cool Cat even tho the lady on the phone said it did.

The connectors are different as are the instructions. Also there is no room in the Cool Cat for the extra control box even if you could figure out how to hook it up.

If you want to upgrade the Cool Cat ask Dometic if they will sell you the digital control board to replace the analog control board of the earlier model. The unit must be removed to do this.

As an aside the new Cool Cat is 10000 BTU, the old one is 12000 BTU. This is due to using the new environmentally friendly refrigerant. There are no mechanical changes.
Harry

[hbn7hj]

This is what the digital Cool Cat thermostat looks like.

https://www.ebay.com/itm/RV-DOMETIC-...-/352112775212

[hbn7hj]

After thinking about it: Go to a Dometic dealer, (Camping World is one) Order the control board, cable, and thermostat for a late model Cool Cat and install the parts. You are at some risk here because no one can tell you the new board will install in the old unit. (It should. I have seen the two boards and they are the same size.) If it works you have a digital Cool Cat for $200 or so. If it doesn't you are out $200. You could limit your purchase to the control board then if it installs you could purchase the cable and thermostat.

You could also take out the original board and compare it to the new one before paying for it. It all depends how bad you want the one degree hysterisis as it is a lot of work.

In any case the unit has to come off the roof for the install. In my case I blew $200 for the wrong control board then paid $1100 for a new unit. Pleased I got the results, not too happy about the cost.

I spent a night in a Kansas truck stop this past summer with the generator running and the A/C compressor switching on and off all night. Never woke up once. Same thing on shore power for four days waiting for the eclipse in Beatrice, Nebraska.

The temperature swing with the analog thermostat is around 10F. Wakes you up all night long. Freeze-Fry-Freeze or in the furnace mode fry-freeze-fry.

It may be possible to put the Honeywell thermostat on a Cool Cat. Nobody has reported it done. Certainly you can do it on the furnace side.
Harry

[ManWonder]

So here's what I did (spoiler alert: it didn't work): I got a Honeywell non-programmable heat pump thermostat and tried running just my furnace with it. I could get the furnace fan to run but never could get it to light no matter what wires I connected or left disconnected. So, for now, i think i'm done with this project.

[hbn7hj]

It should work! Forget the thermostat and short the two green furnace wires together and see what happens. If that works then there should be a way for the thermostat to short them together.

If the fan runs then something else is wrong. There is a delay from the fan turning on and propane valve opening with the ignitor sparking. The fan starting is the beginning of the ignition sequence which includes delay switches.

Was the propane valve open at the tank? Could you hear the ignitor or see it through the window?

[ManWonder]

Originally Posted by hbn7hj

It should work! Forget the thermostat and short the two green furnace wires together and see what happens. If that works then there should be a way for the thermostat to short them together.

If the fan runs then something else is wrong. There is a delay from the fan turning on and propane valve opening with the ignitor sparking. The fan starting is the beginning of the ignition sequence which includes delay switches.

Was the propane valve open at the tank? Could you hear the ignitor or see it through the window?

I know what you mean; I thought the same thing. But I went back and forth between the old and new thermostats and the thing fired up just fie with the old but with the new one only the fan would run (and then of course it would time out and stop after sensing no flame).