Newbie - electrical question, 12V not working

[ccjack]

Just took delivery of a new TT 2 days ago, our drive back home from the dealer is 3 hours - and we parked in a RV storage lot. When I unhooked from TV I went to push the battery disconnect (at control panel by door) to disconnect before storage. However, first I tried turning on 12V appliances / switches and nothing lit up. It was a bit rainy, so I pushed the disconnect in and went home for the night. next day I went back to the TT pulled disconnect out and everything 12 V worked. However I tried again 15 minutes later and nothing.

Since it didn't work, then worked, then didn't work, I don't think it is a fuse or breaker. I am suspecting either a borderline battery charge or an intermittent problem (perhaps with the disconnect switch.) I put a meter on the battery terminals and read 13V (no load). Have not had time to investigate further. Sales dealership has been helpful on the phone, but I am not anxious to tow it into a repair place if I can fix easily myself - even if under warranty.

Any thoughts on what to try. pull off control panel and bypass disconnect switch? take battery to auto dealer and have it tested ? put volt meter to battery wires going into fuse panel (under refridgerator) and see if it reads 121 V when disconnect is pulled out?

Any advice appreciated. thank you.

[wa8yxm]

Always glad to learn hat the problem is.. Thanks for telling us. Glad you found it.

[enblethen]

Thanks for the update/
Happy Travels!

[opnspaces]

Good news glad you got it fixed. The loose ground terminal would definitely explain the intermittent part of the equation. Now take the saved gas money and go for a steak dinner somewhere.

[ccjack]

Success ! thank you all for replying.

Running a ground cable from battery to interior of TT allowed me to verify all of the hot wires (at disconnect and at fuse box) were all good - 13V to true battery ground. However, the red wire in the fuse box measured to the ground wire in the fuse box read 0, so the problem was the ground/ negative wires.

Problem was in the electrical box mounted to the frame. The negative cable from batt. went in and had a ring terminal that was connected to nothing. the ring terminal was sort of resting against the wall of the box. All other wires were connected to each other, etc. (I had earlier checked that box, but it was packed with wires and I missed the loose one in the back.) I mounted it with a ground screw to the box and appears all is working well.

[LittleBill]

opnspaces wrote:
I like the test leads LittleBill. Well I liked them right up until I saw the price. 🙂 I have these and frequently use one to clamp to the battery or whatever and then clamp the other end onto the probe tip for the meter. Link

they were 15 when i bought them, and they are a lot longer then the ones you mentioned, as I also own them

[opnspaces]

I like the test leads LittleBill. Well I liked them right up until I saw the price. 🙂 I have these and frequently use one to clamp to the battery or whatever and then clamp the other end onto the probe tip for the meter. Link

[LittleBill]

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

these are amazing when you have no friends (i mean no helper available)

Test Leads

[enblethen]

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

[ccjack]

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.

[opnspaces]

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.

[enblethen]

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]

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.

[opnspaces]

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.

[opnspaces]

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.