Please help me understand my thermostat

[jovol]

Hey, I'm trying to swap in an Ecobee smart si thermostat on my 2011 big country. I got a little ahead of myself and didn't check the wiring behind my dometic thermostat before buying the smart si and getting all my tools out. Turns out the dometic has a 7.5vdc supply and the smart si needs 12vdc. Can someone explain to me where this thermostat wires originate from? I removed the sliding door behind the thermostat, which gave me access to them but they just go somewhere behind the kitchen cabinets. I'd like to cut that 7.5vdc at the source and splice in a 12v from somewhere.


While we're at it, can someone explain why my camper has two thermostats? I bought the thing a couple months ago, and don't know if this is some previous owner messing around, or it's how these rigs come. What purpose is the 2-wire honeywell on top? I put a meter on the wires and it read nada. The furnace and AC have been functioning fine off the Dometic.

 

[danemayer]

The upper thermostat may be for the Fantastic Fan in mid-coach.

I'm not sure about your Dometic as it looks like an analog thermostat. But the 2011 LCD digital thermostats are wired to a control box above the main air conditioner air return. There's likely a gray box with connectors and wires coming out of it.

 

[jovol]

There's a mystery solved! I never really paid any attention to that fan roof hatch above the kitchen. The honeywell thermostat seemed to be doing something with a motor that opens/closes the hatch. Obviously since it's 30F outside I think it closed it.

Found where the tstat wires run to, as well as a helpful diagram on the control box by the AC. Now I just need to dig around for the red/black 12v wires and splice them to the tstat.

 

[jovol]

Got the ecobee powered up. Now comes the tougher part, I expect. It seems this Dometic system uses ground signals to activate the equipment, whereas the ecobee drives the signals to +12v. Anyone have experience with this? I supposed I can have the ecobee actuate relays... would like to reduce that complexity if possible.

edit: ordered a 4 channel relay board, we'll see if I can get that to work in a few days.