Thermostat not powering on

[JaBnKr88]

Hey everyone,
I have a 2020 376FL and cannot get the forward thermostat to power on. I checked all the breakers and fuses including swapping out the big black 15amp with a normal fuse. When I pulled the thermostat I'm only getting .58 volts to the back. Checked the rear AC thermostat and that one is getting the full 12v. I climbed on top of the rv and the forward AC thermostat wires are getting the same .58v. Does anyone know if the furnace is the primary power point for this system? The furnance is getting 12v but the thermostat wires leaving that area are still sitting at .58v. Thanks in advance.
Josh

[ChuckS]

The control board of course is what supplies 12 vdc down to the thermostat .

The feed to it is often piggy backed onto another 12 vdc circuit . Power is always present at the AC control board and gateway

The furnace control board Does Not supply power up to the roof AC control board. Feed to furance is separate circuit.

The two blue wires from roof AC control board down to furnace control board are “Signal lines” only so the thermostat can tell the furnace control board to turn on or off

You need to find where the roof AC 12 vdc power feed has been lost and fix that to regain thermostat operation

[JaBnKr88]

I appreciate the info, I'll start back on the top at the AC control board and work my way down to the battery to see if I can corner the issue.

[ChuckS]

Originally Posted by JaBnKr88

I appreciate the info, I'll start back on the top at the AC control board and work my way down to the battery to see if I can corner the issue.

** If you find that you have NO 12vdc on top at that AC control board then the thermostat of course wont receive 12 vdc either... My Zone 1 AC (LR unit) gets its 12 vdc power from a piggy back line running to a fused circuit labeled (Misc) in the power center panel..

[ChuckS]

Typical diagram for LCZ thermostats..

Yellow arrow denotes incoming 12 vdc to AC control box

Red arrow denotes 12 vdc supplied back down to thermostat

[JaBnKr88]

Thank you again for all the help. I shot all the power again, thermostat, roof AC, and the breaker panel. The fuses and wires all shot good there but still nothing from the ac or thermostat. Finally found the thermostat line running into the belly of the rv and the only place I could find that it connected to a 12v+ wire was next to the furnance. Pulled the cover panel off the furnance and found a reset/off switch that was stuck in between both settings. Cycled the switch and all power returned to the forward HVAC.