Where does the

[Portiabowen]

We have a 2008 Winnebago motor home we bought used two years ago. The furnace didn't work but the a/c has worked fine. To fix the furnace our local RV service shop had us replace the circuit board with a Dinosaur Universal Ignitor circuit board. Now our a/c doesn't work and we have no power at the thermostat. Fuses, batteries and breakers are all good.  How do we determine where the thermostat gets its power from?  We are going to start here and work from there but not sure what powers the thermostat.

 

[Rene T]

It may be easier to just run another wire from a good power source.
Oh, and welcome to the forum.

 

[Arch Hoagland]

Welcome aboard!!

What did the local RV service shop say when you told them the A/C quit working after they fixed the furnace? 

 

[John From Detroit]

EIther a switch is set wrong or a wire not connected on the Dino Board.

 

[Gary RV_Wizard]

Need more info on the furnace & a/c configuration, but the thermostat is usually wired to receive power from either the furnace or the a/c zone control (multi-zone heating & a/c).  Do you have separate thermostats for furnace and a/c, or all in one?  How does the furnace work if no thermostat?

 

[John From Detroit]

I kind of wonder if the furnace wires were not "Swapped" at some point. there are two blue wires on the multi-pin connector on the Control board. IF your T-Stat is mechanical (NOT electronic) then the furnace does not care which one is HOT and which one is SWITCHED. but the A/C does.