Newbie - electrical question, 12V not working

Oh , and check your fuses, you could have blown something, especially if you sparked the battery. There is a large one that controls all the 12v in the camper. Its more for wiring the battery wrong, but who knows.

thank you all for great advice. a couple comments...

I definitely do not want to modify something and void my warranty. However, would be good to know what the cause is or sequence of events that cause it. I do not want to haul my rig into the shop (at least an hour drive) they try it for 5 minutes, it works, and they send me away.

We did a complete inspection and 12V worked before we left the sellers lot, but intermittent issue got us.

My meter is a Fluke T5-600. Been very reliable, but it is not new - maybe it is getting old and slightly out of cal? It did read 13 and not 13.0, this meter auto scales, I cannot change the scale, I believe it would display 12.6 if it were 12.6. I do have a cheaper meter, maybe I double check with that one.

We do not have a solar panel. We do not have shore power available at the storage site and it really does not work well bringing home with our driveway busy street layout of our home, etc.

I will do some more investigating this weekend.

Ok try this.. Take a photo of the battery.. Any wires hooked to the positive lead paint or tape or otherwise color them RED...

Black on the negative wires

Now remove the battery to any auto-store and have them test it.

NOTE if more than one wire is hooked to a battery terminal. Use a bread tie, or string to tie them all together. that way you don't forget.

The fact it works briefly suggests a very low battery.. When turned off the battery "Recovers" (Reserve capacity) and thus it works again for a few minutes.

You can also charge the battery at home without bringing the Rig.
Use a quality 2 or 3 step charger I use a Deltran Battery Tender/charger/Jump starter. 20 amps in charge mode.

There's nothing wrong with your meter. Or at least nothing wrong enough that you can't trust it for troubleshooting this issue.

Go back to the trailer and turn on the 12v. When it fails check voltage between the tongue mounted circuit breaker posts and the negative post on the battery. If you get battery voltage on one post and a different number (most likely 0) on the other post replace the circuit breaker. If the new breaker trips there is a short somewhere in the system.

New breakers are available at any automotive parts store.

Also check your meter against your car battery. Then start the car and check again. if it reads high 12 off and 13's with the engine running your meter is fine.

Update.

My 12V was still not working in the TT today. I removed the battery and took to an autoparts store and it checked out fine. 12.7v, and 512 CC.

I reinstalled the battery. I also measure 13V (12.7 with my other meter at the battery when installed.) There are two small terminal boxes (ciruit breakers?) mounted to the trailer frame near the battery. Each has 2 posts. All 4 posts measure 12.7 V to frame and the two posts on each breaker show continuity between the posts, so I think those are all good. Everything in front of the trailer on the A frame is measuring 12.7V, at least until the cables go up into the underbelly.

Inside the TT under the fridge is the fusebox. I removed the cover. All of the breakers are on. I measure 0 volts between the big red cable coming into the top of the DC fuses and big white cable coming in the other side top of the row of fuses. I measure 0 volts there with the disconnect switch in either in or out position.

so I suspected the disconnect switch. I did not want to remove the convenience panel (mounted on the cabinets by the exterior door), however, I could see the back terminals of the disconnect switch when looking under the sink. The two big red cables going into the back of the disconnect switch show continuity when in the "on" pulled out position. So I do not think the switch is bad.

So I am out of ideas, I think I need to take the rig into a dealer since it is under warranty. Somewhere between the battery area and the fusebox there is a break. Unless there is a breaker somewhere that I am unaware of.

Have you verified that the battery ground is good?
The red wire coming from the battery should go through disconnect then to a Bat terminal in the 12 volt distribution panel.

ccjack wrote:
Update.

The two big red cables going into the back of the disconnect switch show continuity when in the "on" pulled out position. So I do not think the switch is bad.

How much will it cost you in gas and time lost to take it to the dealer. I would go the Home Depot and buy a 50 foot roll of 16 or 14 gauge wire for $20. Hook one end to the negative terminal of the battery. This is now your ground wire for your meter. I would not focus on continuity but rather on voltage. Take a measure from positive at the battery to the end of your new negative ground wire and remember that number.

Now measure for voltage at various points going back to the fuse box. Every voltage check should be within a tenth of a volt of battery voltage.
Check the posts on the circuit breaker.
Check the big red wires on the back of the battery shutoff. You should get battery voltage with each check. If there is battery voltage at the big switch and no voltage at the breaker panel.

If that is the case can you open a door or remove a drawer to be able to look into the cabinet and the back of the panel? Unplug any power and stick your hand in there and feel for loose wires. If you have to then take the 4 to six screws holding the panel in place and pull the panel out of the cabinet.

opnspaces wrote:

ccjack wrote:
Update.

The two big red cables going into the back of the disconnect switch show continuity when in the "on" pulled out position. So I do not think the switch is bad.

How much will it cost you in gas and time lost to take it to the dealer. I would go the Home Depot and buy a 50 foot roll of 16 or 14 gauge wire for $20. Hook one end to the negative terminal of the battery. This is now your ground wire for your meter. I would not focus on continuity but rather on voltage. Take a measure from positive at the battery to the end of your new negative ground wire and remember that number.

Now measure for voltage at various points going back to the fuse box. Every voltage check should be within a tenth of a volt of battery voltage.
Check the posts on the circuit breaker.
Check the big red wires on the back of the battery shutoff. You should get battery voltage with each check. If there is battery voltage at the big switch and no voltage at the breaker panel.

If that is the case can you open a door or remove a drawer to be able to look into the cabinet and the back of the panel? Unplug any power and stick your hand in there and feel for loose wires. If you have to then take the 4 to six screws holding the panel in place and pull the panel out of the cabinet.

that is a good suggestion, I will try. the reason I checked continuity on the disconnect switch, is I could barely reach one arm back there to reach it, and I could hold my probes like chopsticks and get the two contacts. Putting one probe on a ground up there was too difficult! Aux cable from batter as you suggest solves that problem plus guarantees you are measuring to battery ground.

This TT is mid kitchen. So the convenience panel is about 5 feet from the fuse panel, wires would go through cabinet (with water heater) then under stove and then to fuse under fridge.

Do you have availability of a helper?
Have helper hold one probe on the ground and you check and hold other probe.