Fuse keeps blowing on '74 Sovereign

[Sunnyside]

Hello everyone, my wife and I have been following the Airstream forums since we bought a 1974, 31 foot Land Yacht in January (2013), but this is our first post – So thank you to those who will respond.

The Problem: Fuse keeps blowing

The 50 amp fuse that is shown in the picture ( next to the Univolt, which is not pictured ) keeps blowing now that we have a new battery.

History:

The lighting was very poor prior to that because the battery it came with was over 6 years old and wouldn’t hold a charge. When connected to power at the house or campsite in the beginning, we brought additional lamps into the camper so that we could see well at night, being that we did not yet understand why the lighting was so poor. Recently, after doing a series of updates to the camper, we changed out the battery. We were happy to see that the 12v lights now were all shining brightly, but after a few seconds, the fuse blew, and lights went back to dim again.

Here’s what I’ve already tried: (Airstream was connected to shore power at all times)

1. Replaced the fuse. It did not blow immediately, but blew after turning on a few lights.
2. Replaced the fuse again with all lights off. Started turning lights on one at a time, then it blew.
3. Replaced again and left lights off. After about 30 seconds or so (same amount of time as with the others) the fuse still blew.

The fuses were all very hot, and had to change them with a pliers because of it. After the last experiment, a smell like melting plastic was noticeable in the room with the fuse box and Univolt, although I could not determine the exact location.

Airstream Specs:

Year: 1974
Model: 31’ Sovereign Land Yacht, Rear bath
12v Wire Condition: Original, no modifications
110 sytem: Added one outlet with no problems
Battery: Everstart, Marine, 12-volt, #94, part #27DC

[Splitrock]

Good pictures and great tags. I'd remove the secondary fuses and check the loads one by one with a multi-meter. You did check to be sure the breakaway switch isn't pulled didn't you?

[Airdog]

I have a 72 sovereign that had a similar problem. The lugs were the wire meet the fuse block were loose. I tighten then down and the problem was solved.

[Sunnyside]

Thank you for your replies, I've made sure all the wires were tight, and also I double-checked the breakaway, and it's still together as it should be. But still no luck, I've gone through 11 fuses now and counting trying to figure this thing out.

[Splitrock]

Time to eliminate everything and then add items back one by one. The multi-meter alone may identify the issue. With the battery disconnected and all fuses removed, connect the meter ground to the trailer body and test every terminal. Look for the one with an elevated load reading. Make sure you have isolated the 7-way charge line at the fuse panel.

[Sunnyside]

Update: It's fixed. The problem was the univolt. After tinkering with it some more, I noticed a thin spiral of smoke coming up from the univolt. I immediately ordered a new one, and voila - no problems, the battery is charging, and the lights are brighter than ever. Thanks to everyone who gave some input.