Odd 12V Intermittent Failure

[dclark1946]

We just finished a 2K mile round trip with two weeks of dry camping with no significant issues (other than one single "trailer disconnected" message on the truck's message center on the second day of the trip.)

The other night my wife turned on the trailer exterior led side light and it flashed on and then went out. The front lights would not come on either. I disconnected the side lamp feed connector and checked the Morningstar solar controller status light which was green. A quick DVM reading at the battery resulted in 12.78V and the same voltage was on the input to the 30A CB on the tongue. The output voltage wss slightly lower like 12.6x but I was looking for no voltage. Cycled the factory battery disconnect switch several times but still no lights. I connected ac power so I could open the slide and get to the converter panel in the bathroom. Lights worked on ac. Unplugged ac and figured I would do further trouble shooting in the morning. Next morning 12V power was back and I could not reproduce the outage. So far I have replaced the 30A CB and checked the tongue mounted junction box connections and all nuts were tight and the wires were bright.

Any ideas?

[dclark1946]

I have now checked all the screw connections in the dc power distribution panel pwb and found one that was not very snug. Still need to check battery disconnect connections and keep trying to duplicate the failure.

[jkwilson]

Low voltage systems are less tolerant of loose connections than higher voltage systems. I have seen battery terminals that are on the posts but loose enough they can't feed power without a little wiggling. Check every connection.

[Gjac]

I had a similar one that Darbsen1 posted from HF, what happened is the black knob vibrated loose on two occasions and cause arching between the contacts causing me the same problems. The first time I cleaned the contact surfaces and all was well for a year or so the second time it happened I removed it and now just disconnect the neg battery terminal.

[dclark1946]

A followup question to help troubleshoot this issue. How is the negative connection to the trailer lighting normally implemented? Is there a negative lead going all the way back to the converter panel or does it pick up chassis ground elsewhere?

[dclark1946]

darsben1 wrote:
Do you have a manual battery disconnect?
Mine went bad and I had intermittent 12 volt.
MIne looked like this

Our trailer has a factory installed rotary disconnect switch mounted in the front storage compartment. I did switch this back and forth several times but the lights would still not come on.

[Lwiddis]

wa8 suggested bad bulbs. I would replace those first.

[darsben1]

Do you have a manual battery disconnect?
Mine went bad and I had intermittent 12 volt.
MIne looked like this

[wa8yxm]

I'm fond of saying RVers have a few screws loose.. Likely a Ground connection somewhere (They are often screws) but it could be any connection in the loop from battery back to battery via lamps that sometimes work

EVEN The bulb itself can be the culprit.. Seen that many times.