Intermittent 12v electrical issue

[rexmitchell]

Running the camper on generator power this weekend and cut the generator off to find I had no 12v power anywhere in the camper. Checked all fuses and pulled the fuse panel with zero 12v power coming in. Went outside and battery tested fine, replaced the 30 amp blade fuse just for fun and it tested fine. Got to the junction box and had power there as well. Finally gave up after an hour of taking things apart and figured I’d bring the camper home to mess with it more. Fired the generator up again for some coffee, then cut it off and what do you know…..12v power everywhere. Well problem solved I guess….no. Turn off the generator and go to unhook the battery since I won’t be out for a couple weeks. Just for fun hooked it back up. Nothing again. Shook the wires and it came on. Did it again and lights are back on. My first thought was the connectors but that doesn’t make sense from the original problem where I had power 4 feet away at the junction. Any ideas on what to check or replace?

One other thing I forgot to mention. I don’t recall the green light on my fuse board ever being on this weekend. Not sure if that is related but worth mentioning.

[wa8yxm]

Not a short in the wires. An open. if you had a short you would either pop a fuse or ... Start a fire (Most likely pop a fuse)

But a loose connection... Well I'm fond of saying many RVers have a few screws loose (That's the kind I'm talking about)

OH in the original post you said you had no 12 volts anywhere with the Generator running.. if the Genny is an ONAN.. You had 12 volts somewhere.. the fuel pump is electric. 12 volt house battery powered.

[rexmitchell]

Wanted to close this out. Replaced the connector from the battery wire to the battery and haven’t had any issues since then. Thanks for the suggestions.

[wa8yxm]

Grit dog wrote:
Shook the wires and it worked again is about 95% chance an intermittent dead short in the wires you shook.

Not a short but a screw loose. or in this case a nut on a bolt.

Loose connections act like that.. GM had that problem on the starters of their cars long long long time ago. (like 50 years)

[Grit_dog]

Shook the wires and it worked again is about 95% chance an intermittent dead short in the wires you shook.

[opnspaces]

Maybe open the junction box again, just take the cover off. Use a hammer handle or the insulated screwdriver handle to push all the connectors further into the junction box. Does the cutout happen when you do that? It's possible a wire is still under the outer sheath of a wire nut but not actually clamped down.

[wa8yxm]

You need a test light (most auto stores or auto departments have them) and a spool of light gage wire with a extra clip to extend the ground clip.

Follow the light.. Start by cliping the light's lead to the battery negative and touch the positive if no light try re-seating the lamp bright light good.. move the clip to any non-painted frame part Still bright good. Add the extension lead and try again. Still bright good. Now move out along the positive to each device you find many will have two terminals check both.. Problem exists between BRIGHT and DARK.

NOTE if your converter is an old (I did not look at your profile) Magenetek.. That migth be the problem as it has a relay.. Upgrade to a Progressive Dynamics 4600 IReplaces the "Guts' of the box not the fuse or breaker panels.. You jumper a couple leads ) is highly recommended.

[CA_Traveler]

The wires are grounded to the frame there, might be worth cleaning that ground up.

It's an intermitten problem. Clean or replace everything.

Yes you might get lucky or chase your tail to the next time.

[rexmitchell]

I did check in there. No circuit breaker in the junction. Some wires that didn’t look awesome so I trimmed those and cleaned them up in the box but that didn’t fix it.

[enblethen]

I would look on the tongue where the umbilical cord, battery and rigs wiring come together. Quite often circuit breaker is there in a small junction box.

[rexmitchell]

Don’t have a circuit breaker on the tongue as I thought this was going to be the culprit. The wires are grounded to the frame there, might be worth cleaning that ground up. Nothing I shook today went past the junction which still has me stumped. The wires from the junction into the trailer look good, inspected them first. Can’t wrap my head around the original problem when I had power 4 feet from the battery. I agree there is an issue with a connection somewhere close to the battery but that isn’t what I saw this morning first.

[opnspaces]

You have a failing connection out by the batteries. There's just no if's ands or buts about it. The key now is figuring out where the trouble point is. Start by carefully examining the entire length of the wires from the battery up until they enter the trailer. You might find an abraded part or see a lot of swelling under the wire insulation jacket.

Start trying to isolate smaller sections of the wires between the battery and the trailer. Like grab the wires about 10 inches before they go into the trailer and hold you hand still. Then use your other hand to wiggle that last 10 inches of wire and see if anything happens. Make sure you wiggle, push, pull and bend the wires to look for failures. Then move back further along the wires and try again. My guess is there is a small circuit breaker mounted on the wires and sitting under the tongue. If you try to wiggle the wires at the circuit breaker the posts will move slightly and the power will go in and out.

[rexmitchell]

Thanks, if the power hadn’t been good at the junction originally I’d have said it was the connectors. Just seems weird or that it may have been another problem as well. Going to replace the connectors next week anyway, they look original and that would make them 11 years old. Hopefully that is it.

[CA_Traveler]

rexmitchell wrote:
Shook the wires and it came on. Did it again and lights are back on. My first thought was the connectors but that doesn’t make sense from the original problem where I had power 4 feet away at the junction. Any ideas on what to check or replace?

This is a clear indication of an intermittent connection problem. Most likely source is the battery post connection or the wires. Flooded batteries if that is what you have vent corrosive fumes so check everything. Even shrink wrapped battery wire can/do fail between the wire and connector.

One cheap and clear way to isolate is to completed clean the battery posts and replace the connecting cables. Or using long leads between the post (not the connector) and the far wire end and check for a connection with a voltmeter. Better yet buy a DC clamp on ammeter, leave lights on and check for current to isolate to a wire.

Intermittents can be hard to isolate.