Buzz-Click from 12V Fuse Distro Panel

[MohawkDaddy]

I have an 89 Excella 34'. It's my first Airstream, and after several months at a storage yard, I moved it to a residential lot today and hooked it up to shore power for the first time.

The nearest building doesn't have a 30A outlet, so I went to Home Depot and bought a 20A male to 30A female adapter, plugged in my 30A cord, and plugged the adapter into a standard wall outlet on a 20A circuit.

Now I get some semblance of power in the trailer - lights and fans can be turned on, and the tongue jack articulates.

But now an audible buzz-click can be heard coming from a panel in the front of the trailer, labeled '12 VOLT FUSE DISTRIBUTION PANEL INSIDE'. What I hear is:

Buzz for about 1 second
Sharp click (which sounds like a relay activating, though I don't see anything moving in the panel)
Silence for about 4 seconds
Repeat

When the buzz-click happens, any the interior lights dim, and the tongue jack stops operating. During the silent period, both behave as expected.

I intend to keep the trailer here connected to shore power for some time. By the time it gets hot outside, I'll sort out a 30A power source. But in the meantime ... what's causing the buzz-click, and what can I do to stop it?

And to be clear, I'm not going to be dependent on battery power for a long while. So, if the issue has to do with the charger, can I simply defeat that part of the electrical system (i.e., disconnect the (probably dead) batteries or whatever)?

Thanks in advance --

[idroba]

There is some kind of an automatic resetting 12 volt circuit breaker which is seeing a short and when it automatically resets, it is drawing a lot of power from your 12 volt system. That is why the lights dim when it buzzes, and brighten when it clicks (off). Do not leave it doing that! With time the automatic breaker will fail and may weld itself together in the on (overload) position. That is quite dangerous.

Find the breaker which is doing this (it probably will be hot) and disconnect one wire from it or if it is a clip in type, pull it out. You are going to have to find what it feeds eventually and repair the problem.

If there is no battery(s) in the system now, the + side of the battery terminal may be shorting to ground and causing the issue, but that is just a guess. I don't know how your specific trailer was wired.

Again, find the problem and correct it now. Do not leave it doing that for any length of time.

[MohawkDaddy]

Thank you, Idroba!

Yeah, I left it plugged into shore power only long enough to extend the tongue jack and do a quick walkthrough, turning on lights and such. Figured I'd better kill the power thereafter until I figured out what the problem was.

I'm including a photo of the panel. I assume what I do is just remove the hex nuts and pull off the yellow-tipped wires until I find the offending one? Then I'll figure out which circuit I just killed, and hopefully troubleshoot the short further.

Will let you know what I learn tomorrow!

[idroba]

Yes, that is a good plan to find the offending circuit.

[MohawkDaddy]

Here's what my troubleshooting yielded:

• Disconnect all four yellow-tipped wires on the right side: Buzz-click continues
• Reconnect those wires
• Disconnect all four yellow-tipped wires on the left side: Buzz-click continues
• Reconnect those wires
• Disconnect the big red wire (the one labeled 'Battery Pos 4 ga'): Buzz-click stops. Yay! But now all the 12v circuits are dead; no overhead lights. Also, there's a slight but audible hum.
• Reconnect the big red wire
• Disconnect the red/black wires from both batteries: Buzz-click continues

By then it was too dark to troubleshoot further.

Things I can think of to try:

1. Since the H-shaped distributor bar seems to distribute electricity from the red wire to all the breakers, I thought I could remove the distributor bar and connect the big red wire to each of the breakers, one at a time, until I find the bad circuit.
2. There's a screwed-together wooden box below the distribution panel, which I assume contains the battery charging hardware. Thought I might open this box up and try to remove the charger from the circuit, to see if that helps.

Thoughts?

[wjcwill]

You might try a volt meter checking for voltage from ground to each yellow tipped wires then after you hear buzz click check again to see which breaker tripped. You would think removing the yellow tipped wire from the breaker would stop the bad circuit from tripping the breaker. It could be a bad breaker instead of a short. I have the same setup and don't understand why they used these resetting breakers in place of fuses
Joe

[idroba]

So, it sounds like there must be another auto reseting CB out of sight, on the other end of the red line, or at the converter/charger. And I assume you meant 5 yellow end wires on the left side, not 4 and you have disconnected all of them, 4 on one side, 5 on the other. The bottom right 3 amp CB is not involved in this.

If you disconnected the batteries, and it continues, either you missed one of the bad circuits, or the problem is in the converter/charger it would seem. That assumes there is another hidden auto reseting CB in the converter charger circuit somewhere.

It has got to be a bad short or bad CB somewhere.

[MohawkDaddy]

Alright, found the bad circuit. I did this by removing parts of the copper distribution bar and moving the fat red wire around to each breaker until I found the one that was clicking.

It was the top left breaker that was causing the problem. I didn't see this in my initial 'remove the yellow-tipped wire' troubleshooting, because the panel is behind a couch, and I was working by hanging over the couch ... the downward angle prevented me from noticing the top two breakers.

So, I removed the bad circuit's yellow-tipped wire, covered it with electrical tape, and let it remain disconnected. No more click! Also, no more hum!

I just spent my first electrified hour in the trailer, enjoying lights and an A/C heater. Thanks!

[idroba]

You will eventually find that something is not working on the 12 volt side of the system, and that will give you a clue as to what that circuit operates. Then you will have the fun of figuring out that short.... lol.