The situation
A customer had recently purchased a Furrion furnace and wanted to wire it into a combined AC/furnace thermostat. He asked whether a digital thermostat would work.
The short answer
Yes. A furnace thermostat can be used essentially any way you like, whether it's paired with an air conditioner or not. Digital or analog both work. The wiring will depend on your specific control box and thermostat.
Why
The furnace side of this is simpler than most people expect. Two thermostat wires come out of the furnace, and together they form a circuit. The thermostat just sits in the middle of that circuit and closes it when heat is called for. That's the entire job.
Because the thermostat is functioning as a switch, the furnace doesn't care what kind of switch it is. A mechanical mercury bulb, a snap-action bimetal strip, or a digital board driving a relay all close the same circuit the same way. There's no protocol to match and no handshake to fail on the furnace side.
That's also why your Furrion FFG20RA or FFG30RA is listed as compatible with any brand's 12V thermostat. There is no proprietary requirement on these units.
Where it does get particular is the combined part. Once you're running heat and cooling from one thermostat, the complexity moves to the AC side — which thermostat, which control board, and how the two are terminated. That's the piece worth confirming before you start stripping wire.
Common combined options:
- Dometic CT Thermostat + Control Board Kit — cool/furnace, in white 3316230.700 or black 3316230.714. Thermostat and board together, which removes most of the guesswork.
- Dometic CT Single Zone Thermostat — cooling, heating, and furnace control, in white 3316250.700 or black 3316250.712. Thermostat only — it needs a compatible control board already in place.
- Dometic Standard Relay Control Box Kit 3316432.016 — the cool/furnace relay side if your board is what's missing.
And if you'd rather keep heat on its own control, the Dometic 9610008133 Furnace Thermostat is a digital heat-only unit — a direct demonstration that digital is perfectly at home on the furnace side.
What to do
- Identify the two thermostat wires at the furnace. That pair is the circuit the thermostat completes. Everything else on the furnace is unrelated to thermostat choice.
- Decide whether you actually want combined control. Heat and cool on one thermostat is convenient, but a separate heat-only thermostat is simpler and cheaper if you don't need it.
- Pick the thermostat around the AC, not the furnace. The furnace will follow whatever you choose. The air conditioner is what constrains the decision.
- Confirm whether you need a control board too. Kits like the 3316230.700 include one; a bare thermostat assumes you already have a compatible board.
- Wire to your specific thermostat's diagram, not a generic one. Terminal labeling varies between control boxes, and this is where combined installs go wrong.
- Have a qualified RV technician handle the install if you're not confident reading the diagram — it involves 12V DC wiring and an LP appliance.
Still not sure?
Tell us your furnace model, your air conditioner model, and whether you have a control board already, and we'll tell you exactly which thermostat and board combination to use before you buy. Ask us here.