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Old 10-13-2016, 01:05 PM   #1
Junior Member
Join Date: Sep 2016
Location: Houston, TX - From Gonzales, LA
Posts: 6
Exclamation AC Thermostat Fuse and Shore Power Shocks

I could have easily buried this under the sticky for getting shocked when touching the RV, but with the crazy AC problem and not finding any answers, I feel it is best to mention it in it's own post.

First Mistake... and I know better... I connected my shore power with the largest gauge extension cord I could in my driveway for some maintenance activities. The cord's ground bonding prong was missing, but hey... I had other things to work on that day. This was not allowing the house breaker to trip because there was no feedback through the ground wire. It was only shocking my brother in law... who happened to be wearing only socks. His fault, right? LOL

Don't do what I did. Dumb! Use cords that are 100% functional. These are high amperage services we are connecting to and can be deadly.

Now, onto that ghost in my AC. Every time I would put power on the unit, I would find the DC fuse for the thermostat was blown. I would change the fuse and I could operate the AC. Occasionally the fuse would blow and I would change it again. I asked around with dealers and service folks and no one could understand what I was talking about and gave me the "you must be an idiot" answers. Hence this post!

Thanks to my electrical background, I determined that if I increased the fuse size, the trail of smoke would eventually lead me to the culprit since no one had experienced this problem. It's only 12VDC so who has ever died from that!

I towed my rig on down to Biloxi, MS for Cruisin' the Coast to spend a week with my dad and all was going well... until we smelled that smoke being released from what I assume was the problem area. The AC fuse popped and the fun began. I'd change the fuse, turn it on and within a minute or two you could HEAR! the fuse popping. When I took the inside over off the main cabin AC and opened the plastic junction box, the neutral AC wire nut was melted. **Smoke Located! The white wires were pulling loose from each other and this was creating what is known in electrical terms as a "loose neutral" and it can be a very dangerous situation. This opening of the neutral side of the circuit causes the electrical loop to "seek" a path to close the circuit. I am not entirely sure of how it was finding it, but I do know it was somehow using the 12VDC circuit for the thermostat and that is what was blowing my thermostat fuse. Luckily it didn't ruin the electronic wall thermostat.

Made the repairs and once I got the rig back to Houston I plugged it back in (yes with the same cord, but with reason) to make sure the shock sensation had gone away.

So.... if ever you have a 12VDC fuse blowing and it makes no sense. Check the closest 120VAC appliance to see if there are loose connections on the white/neutral side of the circuits. Hope this helps someone one day. Better yet, I hope this never happens to anyone. I was ready to park over a campfire!

And don't ever... ever, ever, ever use a compromised AC service cord. You are only begging to experience, what I like to call "A sudden attack of deadness".
JoeyNiq is offline   Reply With Quote

fuse, power, thermostat

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