a short in the battery wiring?

ColoradoShel · 09-28-2020, 08:07 AM

After major repair this spring, followed by lots of little tasks I've done to prepare my 2006 T-139 for travel, I've a new conundrum.
A friend helped me install the battery, connecting its wires, but when we put in the 30amp fuse, it blew. The rest of the wiring (when plugged into electric) worked and still works, so it's obviously just related to the battery wiring.

How can I best (quickly and cheaply) get this resolved? Is it likely to be a major undertaking?

Another friend who just bought a used little travel trailer had her son check it out. He brought out his electrical-checking gadget and said that the battery wiring (or maybe all of it) was "backwards" - that an RV is usually wired backwards to a house, but that hers was wired as though it were a house. Who knows? Maybe that's what's wrong with my battery wiring? Has anyone encountered this?

**LJAZ** · 09-28-2020, 10:22 AM

Trailers are supposed to be wired like a house, not backwards to it. Usually you have a black and a white wire to connect to the battery. The black wire should connect to the positive terminal and the white to the negative. Of course there is no way to know what a prior owner may have done to the wiring so colors could have been changed.

If you don't have the ability to trace out the wires yourself you might want to get this professionally looked at. Check to see if you have a mobile rv tech in your area. Usually they are cheaper than the dealer, they come to you and you don't have huge wait times.

APD · 09-28-2020, 05:23 PM

The 120 volt wiring is exactly like a stick and brick.

The converter puts out 12 volts to charge the battery when plugged into shore power if that connection to the battery is reversed at the converter it will blow the fuse when the battery is connected.

And +1 to what LJAZ said....

twinster2 · 09-28-2020, 05:47 PM

Not sure if this would work, but if AC works when plugged in, I would do the following:

1. Disconnect the wires leading to the battery.
2. Plug in shore line power.
3. If the converter is working correctly, it should be charging the battery. Use a multi meter on the wire leads going to the battery to see which one is the positive wire.
4. Once determined the positive wire, connect the battery accordingly.

ColoradoShel · 09-28-2020, 09:48 PM

Thank you, Liaz - I didn't know Mobile RV Services even existed! A great idea.

ColoradoShel · 09-28-2020, 09:59 PM

Thank you, Twinster. You have provided information way beyond what I know!
I wasn't sure what gizmo could figure this out (and I won't know how to use it, either - but I can read, so if there are instructions, there is hope!) I see a multi-meter with good ratings on Amazon for $12.99. I'll buy it now and it will be here Wednesday.

I have questions:
1) Since the fuse is blown in the wires connected directly to the battery, is that the same as disconnecting it?
2) plug in shore line power. Easy, no questions.
3) How can the converter charge the battery if it is disconnected? Or do you mean that the converter should be "sending" a charge down the wire leads that go to the battery?
(And how does one identify those leads? I know some items are marked on the converter panel - hopefully "battery" is one of them - but then is there something on the panel that would tell me pos-neg? That's what the multi meter would be smart enough to do?)

Can you tell I'm completely out of my element?

If it turns out that there actually is a short in the wires, would this multi meter also find it? (How?)

ColoradoShel · 09-28-2020, 10:05 PM

APD, the symptom matches, for sure. Of course, it seems that the symptom could have several causes. But the EASY one is reversed wiring - at the converter, right?

I think that's what all three of you are saying. If my "non-electrical-but-much-more-so-than-I" friend knows how to reverse the wires on the converter and we plug in another fuse, we've either found and corrected the problem, or we've confirmed that it's somewhere else in the wiring.

I think it's worth testing. I'm hoping and praying for the easy answer.

RipVan · 10-01-2020, 10:40 AM

I definitely would NOT reverse any wires coming out of the factory installed convertor! You can test for the output (but not the exact voltage) and polarity of the wires to the battery using a 12v automotive bulb if you don't have access to a multimeter. The fuse in that wire near the battery hookup needs to be intact and it SHOULD BE ON THE POSITIVE WIRE! The 12 volt bulb will confirm it. To do so, hold the fused wire to one of the contacts on the bulb and touch the other bulb contact to the trailer frame. The bulb should light if things are "right"!

ColoradoShel · 10-02-2020, 12:50 PM

Thank you so much, RipVan. That's explicit enough that I think even I can do it!

twinster2 · 10-03-2020, 12:46 AM

I will second that you should not be reversing the wires at the converter. First is to make sure you are getting 12 volts in the camper when the battery lines are disconnected and the camper is plugged into shore power. If so, then you need to check to see if you are getting 12 volts between the battery cables using a volt meter. Problem could be the fuse at the battery or any number of crimped connection that are exposed to the elements. Sorry but I can only give you general thoughts because this is something that can go many different directions as you investigate and traced down the problem. A couple of years ago, I couldn't get power from my battery. Turned out that several crimp wire connections that were near the battery had corroded including the fuse holder. I went through, cleaned up the connections and soldered them with electrical solder and replaced fuse holder. From that point forward everything worked like a charm.