Help with electrical melt down

[jheimann]

I believe that I already know the answer, but since it has not been mentioned, have you made sure that you do not have a polarity mismatch between then trailer and truck?

LOL... yes, I double checked the polarity of the battery and the wiring. Its all correct

 

[CharlesinGA]

I am trying to understand the whole circuit breaker v fuse thing. I found this on an Airstream forum:

When a fault developed, a fuse blows and cuts the power off completely until it is replaced (and the fault is found). The automatic resetting circuit breakers I think you are referring to keep trying to reset themselves and in doing so, keep sending power to the fault, over and over and over. Eventually something fails, like the wire insulation and then you have a potential fire.

Automatic resetting 12 volt circuit breakers are not a good solution at all for the circuits. There are a very few situations that they are useful, and even then, one can question that they be used.

I cannot recommend them.

Again, trying to understand cb's myself

Circuit breakers on the trailer side for the incoming power from the 7 pin (and battery power to the trailer power panel) are quite common, if not the norm.

My Bigfoot has two circuit breakers, one on the incoming from the 7 pin and one from the battery to the power panel, they are manual reset versions, but sometimes you see auto reset breakers. Here is a pic of mine.



There are breakers designed for 12v DC that are used for things such as a tow vehicle feed to the trailer, either thru the 7 pin, or heavy wires such as #4 to a Anderson connector on the back of the tow vehicle to supply a battery to battery charger system in the trailer (used with high capacity systems, Lithium, AGM, etc) Eaton Bussmann 285 Series Resettable Circuit Breakers Surface Mount up to 150A

Charles

 

[tlmgcamp]

Thank you. Not sure of the purpose of an auto-reset breaker. If there is a short, why would you want the breaker to keep trying to close the shorted circuit rather than leave it open until the short is resolved? That said, is it possible that the OP has a short and a bad breaker on the 12v feed that kept the bad circuit closed, creating the meltdown

 

[Jim18655]

Auto reset breakers are a safety item where shutting down the circuit might cause more harm than good. Headlights sometimes have them. Imagine your lights going out in a dark area for a minor glitch. Trailer brakes might also be an application.

 

[tlmgcamp]

Auto reset breakers are a safety item where shutting down the circuit might cause more harm than good. Headlights sometimes have them. Imagine your lights going out in a dark area for a minor glitch. Trailer brakes might also be an application.

I guess it is a design choice by the manufacturers. However, if the breaker can't accurately tell the difference between a minor glitch and a major issue that melts down components with the potential of ending in a fire, I would think that better options are out there

 

[jheimann]

Everyone, I spent some quality time troubleshooting the issue today and found what I believe is the problem. The trailer hitch cable on the camper is connected to the camper in a junction box using wire nuts. Upon inspection I found the wire nut on the 12V accessory wire had become disconnected (fell off). As I pulled/moved/manipulated the trailer harness cable it would twist in the junction box because the strain relief was also loose. I can see where the 12V accessory wire was contacting the junction box when the cable twisted creating a temporary short. This was evident by burn marks on the wires and the junction box.

I bought a new cable with a molded end, to replace the melted one. I used crimp connectors rather than wire nuts and I tightened the strain relief so there is no chance of anything coming loose or shorting out again. Also because it did not trip the 30A breaker in the truck, I replaced the breaker with an in-line fuse at 20A... I figure better safe than sorry.

I hooked it all up tonight and tested it. Everything seems to be working. I put an amp meter in the fuse holder and measured 0.8A on the +12V accessory wire... perfect!

I think I am all set. Thank you to everyone for your help in getting this resolved. I truly appreciate the help!

 

[Alaskansnowbirds]

Thank you for letting us know the outcome. Much appreciated.

 

[tlmgcamp]

Looks like I will be under the unit this weekend converting wire nut connectors with crimp or solder