Dometic AC install......help!!

[gary276]

Removed a Coleman a/c due to age and not cooling anymore, ran fine but didn't blow cold air, got a good price on a Dometic Brisk II. Putting it on the roof was the easy part, the wiring is kicking my butt.

In the top pic is the wires where the old thermostat was installed. The red wire is verified with a meter to be a 12v + and I assume the white is 12v -. The green, yellow, blue and grey are the same as the second pic where the a/c unit mounts in the ceiling. The big red and black wire in the second pic go from the a/c mount area to the furnace. None of the wires in the second pic show any 12v voltage at all.

The big white wire in the second pic is the 115 VAC do the a/c.

The third pic is the figure from the installation instructions for the a/c unit and shows the control box wiring diagram. The plug in the pic that goes to the thermostat calls for 2 12v + and 1 12v - , this is where I get stumped, there are no 12v + wires at the ceiling mount area and only 1 at the thermostat mount area.

The fourth pic shows the cover of the old control box and identifies the yellow, green , etc at the ceiling mount area.

The fifth and sixth pic show the thermostat wire hookup and the plug with labeled wires that came with the thermostat and control box.

As I said before the a/c came on and ran with no problems so I know I had power before.

If anyone has any advice or inputs it would be appreciated. I will call a a/c guy or rv a/c fix it guy I I have to but wanted to try myself first.

Thanks.

[TQ60]

???
Looks like you have basic or stupid control.

Standard house type thermostat coukd work but you also have 2 speed fan which is a different but common thermosrat.

What do you need?

[gary276]

I have the new a/c unit and a new thermostat that came with a new control box. The control box requires 2 12v + wires per the diagram and one 12v -, there is only 1 existing 12v + at the thermostat mount area and no 12v + wires at the ceiling area. The new thermostat will not control the furnace nor is there a heat strip, cooling only. What I need is for someone to help me with why the old a/c unit worked with the existing wires but it seems I need to run another 12v + wire to make the new one work and that make no sense.

[jesilvas]

Your new furnace will control the furnace, all the Dometic single zone LCD t-stats do.

You got a different brand! That's why it's different.

You did get a new control board for the A/C right? Cause it looks like an old Coleman . . .

[gary276]

I bought a Dometic Brisk II and a Dometic single zone thermostat kit that came with a new control box. The pic of the old control box cover was to help me explain where the existing yellow, green, grey and blue wires at the ceiling area were used for with the Coleman. I will not use the thermostat to control the furnace, only the a/c unit.

My problem is the existing wiring in the coach does not seem to have enough 12v + wires where I need them. And it doesn't make sense that I would have to run new wires when the old unit, Coleman or not worked fine with the existing wiring.

[jesilvas]

It's an old Coleman. They use different wiring than Dometic. There's no industry standard.

You have enough wires, just calm down. What wiring is going to your old t-stat location from the A/C?

[gary276]

I got it working, I "calmed down" by going to the beach with my girl and walking around for awhile and then to a late lunch on Friday afternoon, had 2 Tacos and 3 Margaritas and when I got home it was all clear, and you are right there is no industry standard from anything I have seen during my restoration from wiring to skylight sizes.

[jesilvas]

There are standards for wiring, plumbing, fire code, LP, and the running gear. But the wiring can be arranged different like you've experienced.

[Camping25]

Originally Posted by gary276

I got it working, I "calmed down" by going to the beach with my girl and walking around for awhile and then to a late lunch on Friday afternoon, had 2 Tacos and 3 Margaritas and when I got home it was all clear, and you are right there is no industry standard from anything I have seen during my restoration from wiring to skylight sizes.

How do I wire the new domestic air conditioner to the old thermostatic? The new air conditioner wire colors are orange, red, red/white, and black. The old thermostatic wires are grey, green, blue, yellow.

[astrocamper]

When I replaced my Coleman Mach 3 with a new power saver version I stayed with the same brand to keep the wiring supper easy. Took about 20 minutes to complete the install of the new unit. Too late for the opening poster but others may consider making the job easier.