battery not charging while driving until hitting a bump

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abstractbart

Member
Joined
Apr 2, 2016
Posts
5
Location
Edmonton AB Canada
Hello!

I'm new here - just picked up our family's first motorhome for a song! It's a 1979 Vangaurd MV225PF (23 ft?) on a Ford cutaway van chassis, with a 460 cid. There's a few missing vacuum hoses, which probably explains the rough idle and the single stall-out when stopped during the 65km/40 mile trip to bring it home.

My first priority to kindly ask for your help:

Before the stalling incident the headlights began to dim, signal relay wasn't kicking the signal lights on, dash lights dimmed out, all of which made me believe there was a charging issue. Then it stalled and we jumped it on the roadside and I got it moving, but still no dash lights and two little birthday candles where the headlights used to be.

Then I hit a bump! She immediately lit up like a Christmas tree! Stayed that way for the last 20 minutes of driving and manoeuvring into its current diagonal driveway position.

It had previously been set up with dual batteries and, now, still has all the parts connected except for a driver's side battery and positive battery terminal cable. Still has passenger side battery, solenoids on both sides, and a battery isolator in the middle. (There are pictures attached)

Is this box in the middle actually an isolator? Is it possibly going bad and kicked back in when I hit a bump? Maybe the solenoids are crapping out?

Thanks for your help!

First time poster and motorhome owner,
Bart
 

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Yes, they're dirty, but they're locked on tight and making a good connection at the moment. Lots of cleaning to do, for sure! Just doesn't explain it not charging until hitting a bump.
 
abstractbart said:
Yes, they're dirty, but they're locked on tight and making a good connection at the moment. Lots of cleaning to do, for sure! Just doesn't explain it not charging until hitting a bump.
Click to expand...

How do you know there isn't a lot of corrosion between the post an the cable clamp. It was just my opinion. You surely don't have to do it if you don't want to.
 
Yep, fair point but I checked the resistance of both cables between frame and post and solenoid and post and it checked out. I can certainly give it a shot, as it needs to be done anyhow.
 
Check your ground connections too. After 40 years working as an industrial electrician, 1 thing I can say for sure, is that the stranger the problem seams, the more likely it is that it's a ground or neutral problem
 
Very corroded battery terminals will show good continuity using an ohm meter. That being said, I would be looking for a loose connection in the charging circuit. Unfortunately, a loose connection is one of those things that you will have to go from connector to connector to find the problem and do0n't ignore the through the firewall connectors. Looking at the battery terminals, I would start there. Also looking at the corrosion, I would check all my ground connections also.
 
Find the power wire coming out of the alternator and check the voltage. Should show somewhere around 14 V give or take a few tenths. Then, with the engine running take a hold of that wire and start tracing it away from the alternator, Keep your hands on it so it wiggles as you follow it. Listen intently to the alternator while doing this, If you hear the alternator load or unload the next connection you find will be the loose one. The seller of my RV had a charging problem similar to yours and was never able to get it figured out, the loose connection was about 18" away from the alternator, at a multi lug positive BUS bar. It was giving him and his not so good mechanic fits. I fixed it within 15 minutes of getting it home.

Bill
 
First my 0ld joke:  Many RVers have a few screws loose.. and this sure sounds like one of those cases..  HOWEVER....

I once had a car that, sometimes, refused to start.. IT appeared there was a major drain somewhere on the battery when shut off... Finally found it.. Believe it or not the alternator was not properly grounding to the engine block, Now it's bolted in place, But it was not connecting.. I put a star lock washer under the bolt and had no more problems.

I'm guessing you have either a nut or a bolt or screw somewhere on the charge lines that is needs tightening.
 
A bump could mean a sticky relay that is not engaging when it should.  I have a heater fan relay that's doing that right now (new relay on order).

In the photo it looks like a battery is missing, probably the house battery. Are you running on just the chassis battery?  And that big blue heat sink looks like an isolator, probably one of the diode types. That shouldn't affect the chassis 12v system operation, but you could jumper around it if you need to test that theory.

I'd be looking at the alternator first, though. Something there may not be making contact, either internally or adjacent wiring. If you charge up the battery with an external charger, does everything work normally until it runs down again?
 
Thanks for all the tips, everyone! I think I may have found the source of my problem - I'll run this by you and you tell me if you think my theory might be correct, though I have a feeling I had a very dangerous condition that cleared up briefly with a bit of luck:

The seller, right before we left with our new purchase put the big ol' house battery in the side battery compartment while I battened the hatches in preparation or travel. What I did not realise, however, was that he had just stuffed the battery terminals down the side of the bttery compartment, without isolating them from the chassis. What I'm pretty sure happened was, judging by the 3 or 4 small black scorch marks on the wall, that the terminals were getting juiced up and shorting out. When I hit the bump, I dislodged the terminals from the wall, stopping the short circuit, allowing the starting battery to get juiced up again. Probable?

On an aside note, with the house battery being present, the extra (missing) under-hood battery is an auxiliary starting battery, or is there a more significant reason for its (potential) existence?

Thanks!
Bart
 
If it's a gas chassis, the second battery position under the hood is meant for the house battery.  The battery tray is available as an option from the chassis maker as they put a second starting battery there for the diesel chassis or as an accessory for ambulance and snowplow prep packages.

If the battery cable goes to the can solenoid, that's the type that's used to disconnect the house battery in a stock configuration.  Compare it to the starting solenoid on the other battery.  It looks like someone replaced the house solenoid with the battery isolater and removed the control wire from the center terminal.

The battery in the side compartment should be wired in parallel with the one missing from the engine compartment, but if the previous owner made the changes himself anything is possible.
 
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