I just got an '86 Honey RV that's got a 454 in it and am trying to decipher all of the wiring. There's a lot of junk in the front of the RV, some of which needs to be replaced and some of which can probably be removed.

Here is something that was wrapped in tape and comes off one of the two batteries in the front bay. The two batteries are separated by isolators but can be bridged together in parallel using an "emergency start" button next to the steering wheel for an extra boost of power.

It looks to me like this is maybe a thermal switch or fuse? You can see a contactor on the bottom right of the picture. Whoever did this was clearly making it so the contactors were always connected. I can't find any good comparison pictures using google images, searching for "thermal switch" so maybe that's not what it is. Does anyone have any idea? I'd like to know if I should find a replacement for whatever this is for or of I can simply switch it out for a single wire.

electrical picture

  • Welcome to Motor Vehicle Maintenance & Repair! Where exactly do these go to (each end)? I think if you trace it back to origin you're going to be able to answer the question a lot easier. Jun 25, 2018 at 20:21
  • It's in between the positive terminal of one battery and the isolator (the isolator that looks like it goes into the house part of the RV).
    – tbox
    Jun 25, 2018 at 20:24
  • It would help if you draw a simple circuit diagram of how the components are connected including the batteries, contactors, fuses and switches etc. Is there any other wires attached to it, have you measured if theres any resistance? It could be as simple as a mounting, a shunt resistor (for measuring current) or a fuse Jun 25, 2018 at 20:38
  • It may be really ugly, but could you check it to see if it may be a diode? I've not seen them look like that, but wondering if it might be a high amperage type (old school). If it will pass juice both ways, then the only thing I would think it would be is a fusible link or just a post connector (either of which would be made for high amperage). Jun 25, 2018 at 20:41
  • 1
    It could also be a thermal (amp) limiter. A self resetting fuse.
    – Moab
    Jun 25, 2018 at 20:54

1 Answer 1


Thanks to @Moab and my neighborhood auto parts store, I found what I was looking for. It looks to be a crusty old automotive thermal circuit breaker without its case.

Here is what a newer one looks like with the case on:

thermal circuit breaker

  • Hard part is determining what amperage it is.
    – Moab
    Jun 25, 2018 at 23:15
  • Indeed. Any suggestions? Or should I go off the wire Guage that it's supplying?
    – tbox
    Jun 25, 2018 at 23:30

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