No DC power to trailer, batteries good

Wanted to post the resolution of the issue. I hired a RV tech and he found the breaker was inside the V nose of our trailer where the battery cable runs from the battery box. It was a 30 amp breaker. He replaced is with a self resetting breaker.

Thanks to all for your suggestions. I got a lesson from this experience.

X2 on the breaker Mex pictured and advised to use.

That is a Cooper-Bussmann product. Lower current models are available.

linnemj wrote:
Our problem with the DC happened after returning from a 8 week trip. Batteries worked fine for 4 weeks and they test well.

I have been unable to find an inline fuse or breaker to date.

Thanks to all for your help! When it quits raining here, I can continue the search for the issue.

OK then 'reverse polarity' fuses on converter are OK

With a voltmeter check voltage on battery side and on trailer side of 'disconnect switch'....is it really working when you turn it ON?

And follow positive cable from battery to where it goes into trailer.....the in-line fuse (or Circuit breaker) are typically under tongue of trailer (It's like a scavenger hunt)

Our problem with the DC happened after returning from a 8 week trip. Batteries worked fine for 4 weeks and they test well.

I have been unable to find an inline fuse or breaker to date.

Thanks to all for your help! When it quits raining here, I can continue the search for the issue.

I buy 'em by the bag full for $1.48 but for important work they are worth even less. A surface mount genuine breaker available at genuinedealz, allbatterysales, or delcity.net cost about 20 dollars and may save you the cost of a hair transplant. Little breakers seem to do fine in the 15-amp range. 30-amps and above they don't seem to live a reliable lifespan.

Battery almost new...........

Have you had this 'no DC from battery' issue since new battery was installed OR something that has just happened?

Since new battery install.......Check on converter for large amp fuse(s) (30A or larger). Could be on front or backside of converter. They are 'Reverse Polarity' fuses. IF battery got hooked up backwards...they blow. No DC from battery but DC from converter works. No charging of battery by converter either.

Bad disconnect switch
Bad in-line fuse/DC circuit breaker under tongue
Blown Reverse Polarity fuses

I had the same problem awhile back. It turned out to be a circuit breaker.Looks something like this

Get out your multimeter. Check that you have power on both sides of the battery fuse, then check both sides of the cut-off switch, finally check power as it comes into the 12v distribution panel.

At some point you will find 12v on one side of something and zero on the other. Clean, tighten, or replace that item.

And yes there are sometimes a breaker that is well hidden with poor access.

We had a circuit breaker installed under the rig near the front. I never knew it was there until our DC died at the dealers. It was the kind that had to be manually reset! The dealer changed it to an automatic reset model.