Hunter thermostsat conversion problem

[DeansDad]

I decided to do the Hunter 42999B conversion on my TT as the Duo-Therm thermostat was like all the others.
I have a Dometic Duo-Therm 13,500 roof air, and I THINK an Attwood furnace (if need be I can remove cover to check).

Here's what I did:

red wire was on Duo-Therm +7.5 terminal, I didn't use it

yellow wire was on Duo-Therm cool terminal, to Y on Hunter

white wire was on Duo-Therm furnace terminal, to W on Hunter

blue wire was on Duo-Therm hi fan terminal, temp not used

orange wire was on Duo-Therm fan terminal, to G on Hunter

green wire was on Duo-Therm gnd terminal, to RC on Hunter

I left the jumper from RC to RW in the Hunter

Also, the small switch is set for HG

I have the furnace working properly, but when trying A/C all I get is the compressor running, no blower fan. Also, there is no fan when the manual fan position is switched on, either.

This seems so simple a conversion, can't believe it's not working right.

[DeansDad]

Update on my conversion:

Chris was correct - I had to have BOTH the blue & orange wires (fan wires) on G to make the cooling fan come on..... I haven't added the switch, as my dealer in Texas said the low speed would sometimes allow a freeze-up to occur.

I totally missed the switch wiring showing the switch adds the 2nd wire to the circuit.

Additionally I believe the pins were not making contact between the thermostat & mounting base properly - I remounted the base as I had an over-sized hole for one screw. After The solid mount it clicked together like it should have.

The only thing is that the A/C fan (not compressor) turns on when the heat is on (furnace fan also works then). But I guess it just circulates the heat better as there is no cooling, just air movement.

This mod keeps the A/C w/in 1 degree, and also seems to start the compressor better (no more short cycling and buzzing, just instant starts).

Thanks for the help!

[billyboy]

I put a 25.00 honetwell in , and it works fine and has a backlight which really is great for the dark hallway

[dieseltruckdriv]

midnightsadie wrote:
ok I gotta ask, why are people changing the stats?

I changed ours out to a Honeywell smart thermostat like we have at home. We only need to remember how to run one 'stat that way. Second, it is nice to have a fairly cool temp set at night when we are under covers, then warm up in the morning before we get out of bed when we are boondocking early and late in the year.

The AC is set to high fan only for me. I don't do hot weather well at all.
This is one of my favorite mods to our 5er.

[Chris_Bryant]

DeansDad wrote:
Am I reading correctly Chris, I should hook orange & blue wires together?

Both on G terminal of Hunter unit?

Duh, dumb question.... I won't short out the PC board in the roof unit if I try something, will I?

Yes- for high fan. Low fan should work with just the orange wire on the G terminal though.

You really shouldn't be able to hurt the board- normal test is to hook all the wires together for hi-cool.

[LarryJM]

donn0128 wrote:
Did you add the SPST mini switch? You need it in the system to make the AC fan work correctly. AC fan is normal high speed.

That is mostly wrong and misleading since as others have mentioned you only need the switch if you want to have and be able to select the =HI or LOW A/C fan speed.

Larry

[DeansDad]

Am I reading correctly Chris, I should hook orange & blue wires together?

Both on G terminal of Hunter unit?

Duh, dumb question.... I won't short out the PC board in the roof unit if I try something, will I?

[DeansDad]

As you can tell, I didn't add the hi/lo switch yet as I wanted to be assured all was working.
Have re-installed the Duo unit to get A/C for now.
Fan works correctly in auto/manual & hi/lo on Duo unit.
I jumped orange wire (marked fan in Duo) to green wire (marked grd in Duo). Fan came on, both hi and low speeds as selected.

[Keith_Smith]

Thanks for the catch Trailrider. I was so excited to get to return some of the much appreciated advice I've received that I didn't fully read the original post.

[wmoses]

midnightsadie wrote:
ok I gotta ask, why are people changing the stats?

When I change mine it will be for two reasons - more precise temperature control and also I want to be able to have it automatically switch down to a night setting to conserve on electricity and to be quieter.

[Chris_Bryant]

Just to clarify, the analog DuoTherm units (no longer available), switch grounds to activate the relays in the rooftop unit. Coleman /RVP units switch +12 volts to activate relays. Also, as I said, the orange wire turns the fan on, the blue toggles between high and low. If you just ground the blue, you will not get any fan operation.

[trailrider]

Good point but the OP said he hears the compressor running so he is past the time delay feature.

[Keith_Smith]

I had the same problem last summer when I replaced my Duotherm thermostat with a Hunter. What I didn't realize at the time was that new thermostats have a built in delay to protect the compressors during situations where powers will go off and right back on( like during a thunderstorm). It takes 2 1/2 to 3 minutes for the AC to be triggered to come on. Originally, I thought I had a bad thermostat when the AC didn't come on. I took the Hunter back to Lowes and got a second one with the same result. I went to the house disgusted and when I came out an hour later the AC was running. I turned it completely off. I resorted to calling Hunter and the tech politely explained this to me. Embarrassingly, it was on page 25 of the manual. I went back to the trailer, turned it back on and waited a few minutes and it powered right up. Worked normal after that.

[Chris_Bryant]

To the OP- the wiring looks good- try jumping between green and orange to see if you get low fan then. The only oddity is that DuoTherm uses orange to energize the fan and blue to switch between high and low- so even though blue is listed as high fan, you must ground both blue and orange to get high fan.

[Old-Biscuit]

midnightsadie wrote:
ok I gotta ask, why are people changing the stats?

Because the analog t-stats over shoot set point by 2-5 degrees
The swap is to a digital t-stat which controls to set point +-1 degree

OP.....
I did the swap without using a mini switch but I wired it to use high fan speed (low fan didn't more enough air for me)