12v DC system failing sporadically

[MJ_Remy]

I have a 1997 Tioga Montara (Ford E350 V10 engine). Nice rig, works well.

I disconnected from shore power 110v, and suddenly the 12v DC battery systems would not work. Lights, fan, water pump, etc would not come on. I plug it back in, and it all works. I run the generator, and it all works. I disconnect from 110v power and it fails again.

I discover the 2 100-Amp newer AGM batteries are very low. I plug in overnight, and they are fully recharged. However, nothing works after I disconnect.

After 1 hr, the 12v DC system works perfectly well again on its own. What is causing this problem? I research the web, and the next day I call some RV places. This is what they said:

1. Could be the solenoid on the converter that is failing.
2. Could be the charge unit on the converter.
3. Could be a wire to the battery.

In my older rig, I think my converter is very slow to recharge the house batteries. Even after a whole night of being plugged in, the fully charged light does not come on. I use a separate trickle charger to recharge fully.

Do I need a new converter?
Do I need a Converter/Charger (newer gizmo, faster/fuller charge on batteries)?
Do I need to unscrew Converter and check in back for loose wires/ dust?
Do I need a new solenoid for existing converter?
Do I need to find and reset a hidden circuit breaker on ...?

Please help. I would appreciate some specific items I could check. I am full timer RV'ing out of necessity, so it is critical that things work. Thanks in advance!

[wgriswold]

I have had this problem twice.

The first time the battery disconnect was failing and finally failed completely.

The second time it was the 30 amp fuse that was 3" from the battery on the positive wire. The fuse holder had failed/melted and the fuse was intermittently failing to connect.

[time2roll]

You have an intermittent open circuit. Get out your meter or test light next time you have no power. Start at the battery terminals to check voltage. Then move along to the stack of 12v fuses. At some point you should find 12v on one side of something and zero on the other. Tighten, adjust, clean, repair, replace that device or connection.

[DrewE]

This sounds like a loose connection to me, as well. I would start by verifying all the wires and connections at the batteries, the positive and grounds and battery interconnect wires. I have seen cases where battery cables corroded internally, within the insulation, to the point of being disconnected (or nearly so) while outwardly appearing sound at first glance.

Also check the ground connection at the frame from the battery ground cable and clean/tighten if needed. The fact that things work well when connected to AC power seems to indicate that the main 12V wiring is in good order and the problem lies somewhere along the wiring between the batteries and the rest of the system. It's not a guarantee that your problem is there, as electrical problems can be quite subtle, but it's a pretty good indication.

[Sam_Spade]

1492 wrote:

Worth repeating occasionally BUT......

The sheer number of mis-directed posts that end up there should make it obvious that the NAME of the sub-forum needs to be changed.

Unless and until that is done, it won't get much better.

Apparently the owners can't be bothered with trivial stuff.......like making their product less confusing. 😞

[1492]

[ksg5000]

The DC works when your plugged in which would seem to indicate that your converter is working - you can double check that by using a multi meter and taking a reading (preferably at the converter).

Your rig has a battery cutoff switch - often a momentary toggle switch maybe located near the door of perhaps near the drivers left knee in the cab - make sure that's working properly and not stuck in the off position.

Another possibility is defective auto reset circuit breaker often located near your coach battery. Here's a link to what it might look like https://www.amazon.com/MonkeyJack-Reset-Circuit-Breaker-Automatic/dp/B075GRYFTL/ref=sr_1_10?s=automotive&ie=UTF8&qid=1505816112&sr=1-10&keywords=auto+reset+circuit+breaker+12v

You should also have your batteries tested - any tire or auto shop will perform for free. If you have lousy batteries then they will only hold a charge for a short period of time which would explain why you lose power when you disconnect from shore power. The battery status indicators on RV's are worthless so don't rely on them.

When I had phantom 12 volt issue I finally tracked it down to a loose battery wire - apparently the connection between the wire and terminal ring (hidden under shrink wrap)came loose. That was a nightmare to track down.

[KX5002]

Always check connections on low voltage systems, a little dirt or corrosion is all it takes.
Pay special attention to the ground connections, bad grounds can cause funny things.

[darsben1]

When mine went bad I took my rig to Camping World to diagnose.Exactly the same thing I told the Service writer that it was intermittent on 12 volt. They plugged unit in to check. Of course it worked through the converter.
When I got the unit back the 12 volt did not work in the parking lot of CW but it still worked intermittently. My wallet was lighter but I still had the problem. Enough venting though.
What was wrong was the Battery disconnect had gone bad and it only made connection part of the time.

Looked like this


Part cost $12.00 plus the time Camping World ripped me off for. So about $212.00 all in.

[Sam_Spade]

What you NEED IS......
A multimeter so you can test the voltage at various points to narrow down the problem.

Guessing and throwing parts at a problem like this often turns out BAD....meaning time consuming and expensive.

Most likely causes:
Loose or corroded main battery cable connection.....including the main battery disconnect switch/solenoid.

Intermittent open connection INSIDE one of the "newish" batteries.