Digital Thermostat

[Tim295]

One of the things I noticed when using the AC (and also the heat) is that the trailer often would be too hot or too cool. I researched and found a popular fix was to swap the mechanical slide type thermostat with a digital one.

Here is my version of that mod:

The original Thermostat has a High/Low Fan speed for the Air Conditioner. That feature is not found on most home type thermostats, and I ended up buying the Honeywell RTH2310 programmable digital thermostat. I initially installed it and just omitted the low speed wire.

After using the AC on my last weekend campout, I realized the low speed would be nice as it runs a little quieter and it would cycle on and off less in order to maintain the temperature better inside. I used a SPDT switch that takes the fan command from the thermostat and simply routes it through the contacts to either the high or low speed circuit. It was small enough to fit inside the case and only required a ¼” mounting hole.

I soldered short lengths of 18 gauge wire to the connections.

And then I covered them with heatshrink tubing.

 

[Tim295]

Due to a limit to number of images, here is the next part of the digital thermostat modification:

The high (green wire) and low speed (light green wire) pigtails are tied in with wire caps and pushed back into the wall.

The center common of the switch is tied to the Fan output terminal (GL)
The Red wire goes to the AC Compressor turn on signal terminal (Y)
The White wire goes to the Heater terminal (W)
The Red/White wire goes to the Heater terminal (Rc) which is has a jumper to (Rh)

Here is a diagram of the wiring before with the old thermostat:

And here is the new thermostat wiring diagram:

 

[Tim295]

And here is another pic of the high low switch:

 

[coal]

Very good info and schematic too, this is a mod that I want to do.

 

[Terry-JAY]

Great Mod Tim!

Do you have a ducted AC system and can you hear/feel much difference from high/low?

I was not able to tell any discernible difference in my AC from high to low so I omitted that switch....so now I am wondering if maybe the high/low on mine is broken and it is stuck on high.

 

[SmokerBill]

This is definitely a mod I need to do. I was going to try setting mine up so "Fan Only" used the furnace fan, not the AC fan, so I could use it anytime (no shore or generator power needed). But, looking at the furnace schematics, it's just not possible. There's no option for fan only with the furnace.

Dang it!

Still need the digital thermostat upgrade, though.

 

[Tim295]

Great Mod Tim!

Do you have a ducted AC system and can you hear/feel much difference from high/low?

I was not able to tell any discernible difference in my AC from high to low so I omitted that switch....so now I am wondering if maybe the high/low on mine is broken and it is stuck on high.

Thanks for the comments.

I do have ducted AC. There is a definite difference in fan pitch/speed when the switch is moved from high to low, although there is only slightly less noise.

If you changed out the original thermostat with the high/low fan feature and put in a digital home type thermostat, you are only going to have it "stuck" on high or low. It depends on if you wired the thermostat fan output to the high circuit (green wire on mine) or the low circuit (white wire). I think I remember reading a post where someone wired it to both. I'm not sure what the results would be with that.

 

[Terry-JAY]

Thanks Tim - yeah I was referring to when I had the stock thermostat. I could not tell any difference between high and low so when I put in a digital, I just wired to high and left low disconnected.

My guess is my control board may not be working properly. I tried to remove the wires up in the AC unit at the control board to check them, but they were connected so tightly I was afraid I was going to damage the connectors trying to get them off so I stopped. Have not had more time to experiment, but not sure it is really worth the time and effort since I like a lot of air flow anyway. I generally leave the fan set to on all night so I get a nice breeze.

 

[kcconawa]

Following the modification, did you test the heat cycle to also make sure that works?

FYI - my thermostat went out in Florida and was replaced by RV mechanic. Everything was fine all summer but when got to winter in North Carolina hills , found out the replacement thermostat would not run the 2 speed furnace on my Designer. Had to pay another service call buy another new thermostat etc. .....

 

[Tim295]

I did the mod a few months ago and only recently added the hi/lo switch. The heater was the only thing I used for the first three weekend campouts. I only got to use the AC on this last weekend. Both heat and AC work great.

 

[norty1]

Great mod and even better instructions. I don't know they they are still using the old thermostats but I plan to do this one also soon.

 

[edatlanta]

The high/low fan only is functional with my a/c. It does not work when in heat mode. This was the case before I changed my thermostats from the original to digital. I decided on the Coleman Mach for my replacements because I didn't want to do anything to potentially cause a problem with my warranty if something comes up. I agree the other replacement brands are a lot cheaper than the Coleman, but I used the Coleman for the reason above.
They do work much better than the original. Most of the time the temp never changes where before the change it would change as much as 3-5 degrees.

 

[Wiscampsin]

One of the best mods I did on all 3 of our campers. Thanks Tim for a great tutorial and pics. It'll help others who haven't yet done this inexpensive, easy and beneficial mod.

 

[Rustic Eagle]

snip.......I could not tell any difference between high and low so when I put in a digital, I just wired to high and left low disconnected.....snip

There was a little difference in low/high with my A/C fan, but wired to high as well on my digital upgrade. I'll save this mod thread in the event I decide to add a switch in the future.

Tim, nice write-up on adding the switch!

Bob

 

[Big Jim-JAY]

Just installed mine today!!
Bought the Honeywell, didn't do the hi/low switch mod.

 

[yddad45]

I just wanted to thank 22FB2010Tim for his post on how to wire a digital thermostat. I installed two Universal Digital Non-Programmable Model: 42122 thermostats in my Rv today. At first I was a little puzzled how to wire them but after looking on JOF and finding 22FB2010Tim post it was a simple install.
Thanks again 22FB2010Tim it helped me out alot.:hihi::hihi::hihi:

 

[Jrmay25]

Can't wait until my digital thermostat's arrive and I am able to install them. I ended up finding a place online (rvplus.com) that has the actual Coleman specific thermostats for $66.00. I ordered 2 and they should be here within the next day or 2 so I will let everyone know how the install goes.
FWIW I found a Honeywell digital thermostat at HD for around $20 but it didn't have room inside the case for the HI/LO switch so I took it back. Figured for a few $$ more I would save myself the headache and replace them with ones I should be able to hook right up.

 

[Lady Fitzgerald]

Can't wait until my digital thermostat's arrive and I am able to install them. I ended up finding a place online (rvplus.com) that has the actual Coleman specific thermostats for $66.00...

How did you figure out which one to get? Their details are rather sketchy.

 

[edatlanta]

X2 Jrmay25. I used the Coleman replacements as well. I didn't want any warranty issues if something came up during the warranty period.

My dealer gave me the Coleman digital numbers to order. They said they could do the exchange, but since it is wire for wire and two screws.......I did the labor myself. It takes about 10 minutes each to do the exchange and that includes getting out the screw driver and putting it back up.

 

[Big Jim-JAY]

WOW!!! What a difference!! Cycles more often, but keeps it nice and cool!!
It was 106 yesterday!!!
I will do the hi/low fan mod.