12 volt circuit breaker tripping

[Leyland]

I have a 2017 Montana 3791 RD and have the 12 volt circuit breaker tripping and resetting. It is not the one going to the hydraulic pump. This is the one that feeds other 12 volt stuff in the unit. I have narrowed it down to one red wire. I disconnected it from the breaker and no more problem that I can tell with the exception the furnace will not come on. I have turn off the switch. At the furnace and it still open and closes when the red wire is connected. Don’t really need furnace here in Georgia right now but need to get it fixed soon. I replaced the little circuit breaker and it still tripping / resetting when the red wire is connected. I don’t know where this wire goes . I checked the panel box and don’t see a red wire on the fuse link for the furnace. Need advice ….
Sorry for the long post but wanted to let you
All know what I have done and narrowed it down to.
Open for suggestions …. Thanks