Have RV Questions? Ask an RV Mechanic Online.
What is the make and model of your furnace? Do you have a small digital multimeter so you can take some actual DC voltage readings here? That would make this diagnosis much easier. R.J.
No hurry.............I am here every day off and on. I will watch for your post and then we can sort this out for you.
There is no 110 VAC here.............only 12 VDC on this furnace. That was the limit switch in the photos. Take and jump across them so that it isn't in the circuit and try it. IF it works then you have the answer. Poor contact in the switch............rare, but it happens. Usually, they just go bad. Let me know what that result is.
Let me give this some thought and get back to you......
When you jumped across the terminals of the limit switch.......did you disconnect the wiring from the switch and then hook the two wires together?
There is no really logical reason that this works fine on shore cord and then blows a fuse on the battery only UNLESS the battery has got a short in it OR the motor is failing. Those are the only possible causes for that. Start by having the battery load tested, even if it is brand new. Even new batteries go bad and can have an internal short. Then if that checks out good and the voltage is over 12 VDC, try it again. Let me know what happens.
I know and that is what I was trying to explain to you. IF the motor is failing for bad brushes and/or bad bearings, then it will have to work harder at lower voltage............that drives up the heat in the circuit and blows the fuse in the thermostat. When you have more voltage you overcome that problem. No other explantion that I know of. I have been at this a long time.
There is usually a circuit breaker in the furnace that may have tripped or it may be the main fuse in your load center. The longer it goes the worse it gets. I think you are just going to have to buy a new motor.
Did you read my last post..............there is a main fuse in the load center that controls the power for both units on the thermostat.
There is another breaker in the furnace on most models........and I hope you didn't burn up the thermostat by jumping the fuse in there. That is why they put fuses in them.
Yes...........and the power to the thermostat comes in from the furnace. See the diagrams on the attached link.
Link to a better manual on these............
So was it the motor? Let me know if we need to dig deeper on this as all follow ups are included in our fee. I will be around all week-end.