Dead RV trailer battery when getting home

There may also be a fuse on the trailer. THere was on the trailers I modified.

2oldman wrote:
Never heard of a second battery for the trailer. If so, yes, it should be deep cycle.

Yes my 2004 chev was available with an optional second battery, assuming of course you had a truck camper. This same circuit would also power the 7 pin trailer socket.
Agree, deep cycle would be better.

2oldman wrote:
Never heard of a second battery for the trailer. If so, yes, it should be deep cycle.

Some Deep Cycle batteries may not tolerate under hood temps though.

Never heard of a second battery for the trailer. If so, yes, it should be deep cycle.

I think I was able to figure it out. So the power wire doesn't go from the battery area to the trailer plug. It goes to a relay or isolator at the secondary battery. The trailer plug is powered through the secondary battery. The issue is that relay is toast so it wasn't allowing power to the trailer plug. When that died it shorted a bunch of stuff and blew a bunch of fuses, some were hidden... So once the new relay comes in then in theory I should be up and running again.

Another question is shouldn't my vehicle secondary battery be a deep cycle rather than a starting battery? It appears all that battery is wired to is the trailer plug. Well other than the relay which allowed it to be charged when driving. Chev even told me they use normal batteries. But I'm not sure why you wouldn't use a deep cycle if all its powering is your trailer when parked and not running.

Any chance that the refrigerator was accidentally switched to 12V when you left the campground?

Check that the wire going into the 7 pin connector at the rear of the truck has power. It could be that the wire connection to the pin is bad.

Iraqvet05 wrote:
GM is notorious for not equipping the Silverado and Tahoe lines with the proper fuse and/or relay for the trailer the trailer charge circuit and aftermarket brake controller wiring harness....in fact, they leave the wires disconnected near the distribution box under the hood. Check eTrailer and Google for your specific truck relating to this. I know many GMs have to be in tow/haul mode for the circuit to energize also.

Not true at all on any GM truck I've owned ... yes, you might have to add a fuse to Stud #1 in the under hood fuse box and although I know that during some model years the charge line wire itself sometimes was left disconnected during the vehicle assembly that's never been the case on any of the 3 GM trucks I've owned. GM doesn't use a relay in the charge circuit as does Ford, again at least not on any of the trucks I've owned. Also, this charge line (+12 vdc) on Pin 4 of the Bargman connector, once activated, is hot all the time, even if the truck isn't running, and has nothing whatsoever to do with whether the truck is in Tow Haul mode or not.

Bargman 7-pin Pinouts

The fuse is good and shows good power. But somewhere between the fuse and the plug the power is lost. I have a feeling it's something to do with that secondary battery but don't know anything about that.

OK you have an open circuit between the fuse and the connector.
(I assume the fuse actually has power)