Wiring problem with thermostat controlling furnace?

[Crossfire2200BH]

This is a wiring question related to a thermostat upgrade.

I've upgraded from the manual control ceiling assembly on my stock GE rooftop AC to a wall-thermostat-controlled assembly (details below). The upgrade is working really well for AC control. However, the upgrade is meant to control of the furnace, as well. But the furnace isn't coming on. I need some help figuring this out.

The details:
My stock 2021 Keystone Bullet Crossfire 2200BH came with a Dometic furnace, controlled with the simplest of wall thermostats:


and the dumb manual ceiling controls (GE RARMN1A) for the AC:


But GE (Camping World) offers a wall thermostat upgrade kit for the AC unit, and the thermostat also supports a separate furnace. (Model numbers RAREN1A Non-Ducted Ceiling Assembly, the RARMC2A Control Box, and the RARWT2B Black Thermostat)


I couldn't find an installation video for exactly my use case, but found two great ones from GE for the very similar ducted version: "Installing the RARED1A"

https://www.youtube.com/watch?v=5xCo1OGxh-s

and "Upgrading your existing RVAC with a GE..."

https://www.youtube.com/watch?v=nkgy3GpDL6k

Following a mix of these instructions, everything went fairly well. The GE wall thermostat is controlling the roof AC unit properly. But the furnace isn't coming on when it should.

I removed the very simple Dometic furnace thermostat and ran the two wires from the back of it to the RARMC2A control box, instead. The first video suggests all I have to do is run those two wires to the two Blue/White wires of the RARMC2A. The second video suggests it is important to also splice 12V+ into one of those wires. I've tried both wiring options (with and without the 12V), but neither seems to activate the furnace.

So, two questions, 1) should 12V+ be spliced into one of the furnace wire-to-blue/white wires or not? and 2) what am I missing? What might cause the AC portion to work well, but the furnace control not to work? Thanks.

[Emtsrus]

How do you have the dip switches set on the thermostat?

[Emtsrus]

Looks like on the thermostat, #1 off is for cool—on is for heat pump whichever one you have, and #2 and 3 are not used then #4 should be off on the dip switch for furnace to run. If the #4 is on, that locks the furnace out of the system.

[Crossfire2200BH]

The AC unit is equipped for cooling only with no heat pump. All 4 DIP switches on the thermostat are turned OFF.

[Emtsrus]

Did you have to direct wire the control box, if so the white terminal is the furnace control terminal. Can you send pics of the old thermostat wiring and terminals?

[chuckster57]

Is your AC Dometic? looks like in the video you have to have a GE AC on the roof.

I see you do have a GE Ac on the roof. The two wires that ran to the original thermostat, Did one have 12VDC when tested?

[Emtsrus]

You may have this already but if not, here is the wiring diagram for the control board according to the model number you supplied. Looks like the furnace hooks to the blue and white on the furnace relay. More pictures would help to figure it out if you have all that hooked up right.

[Crossfire2200BH]

Thanks, everyone. It is working perfectly, now.

The first of the videos was right. I disconnected the red and white thermostat wires that were previously connected to the OEM thermostat and connected them to the red and white wires in the new thermostat wire running from the new thermostat to the ac control box. At the control box, I connected to the two blue/white wires, one to the red thermostat wire and the other to the white thermostat wire.

Lastly, I found the power reset switch on my furnace, cycled it off and on, and everything worked!

Thanks for the encouragement and insights. They kept me going until I got it figured out.