Weird electrical gremlin I cannot figure out.... Noticed the truck was turning over a bit slower than normal. It started barely and I took it for a drive, I noticed that the wipers are slow and the battery volt gauge is showing lower than normal. The longer I drive the lower the battery volt meter goes however the battery light does not come on (It comes on when i turn on the key with the truck off so I know the bulb is good I drove for about 45 minutes and the voltage got down to about 8. Stopped at a shop, and turned it off thinking it would not turn over. I was wrong, it fired up again! Test shows 14.3 volts on the drivers battery and 10. 2 on the passenger battery. Replaced the passenger battery thinking it had a bad cell and cleaned the terminals and all was good, took the truck for a 500 km trip with no troubles.

Truck sat a week or so and I drove it again today and noticed the same problem with low voltage on the gauge and slow wipers. Checked the batteries and again the drivers battery is charging with 14 volts and the passenger battery is at 11 volts..

Ideas?

 

Did you check the ground cable ? Not the end that goes to that battery, the other end that grounds out

 

im leaning to agreeing with CJ there... sounds like possibly a bad cable.. if its charging the one and not the other that seems more like the issue to me as well...

 

yep that's pretty much all it can be is a cable or cable connection. Start with the ground since it's cheaper and easier, or it might be time for a new positive cable. Sometimes they get packed with corrosion right where the terminal end is crimped on under the insulation where you can't see it without cutting it open.

 

Thanks for the replies guys. So I traced back the ground wire on the passenger side and what do you know, its flapping in the wind not connected to anything!! Perfect I thought I have it fixed, connected it to a decent ground on the frame and took the truck for a drive.... Same problem! Ran the truck until it actually stopped running due to no power (dash went dead) then I turned off the key for a couple minutes and she cranked right over and started again. (I am guessing the drivers battery is slowly charging the passenger batt while it sits) I checked the voltage while running and the drivers battery has about 14 volts and the passenger has 10 or so. With the truck off the passenger goes up to 11 and drivers around 12.

So I am thinking it has to be the positive terminal "through" connection on the passenger batt, it has the lead from the alternator, lead to the starter and lead to second battery all going into it. The ground wire also has a couple of smaller leads off of it that go to the frame one on the top near the batt and one on the far end which was probably what made it work for the last who knows how long.

Finally I checked it one more time running before I came into the house and the drivers battery was only at 12 and the passenger at 10.. Anyone have a match?!? hahaha

Thanks again in advance!

 

One thing to keep in mind when parallel batteries are mismatched badly is don't try to charge them using the alternator. First, test both individually to make sure they are serviceable with no shorted cells. Make sure all cables and connectors, grounds and such are clean and tight.

Remember batteries connected as such make up one large battery from an electrical standpoint. Charge them slowly in parallel at around 20 amps using an outboard charger and monitor the voltage and current. It may take along time.

 

Bad cell maybe....do you have a load tester

 

I thought bad cell at first too, replaced the passenger battery and still the same problem. The drivers battery is less than a year old... I guess I could swap another known good battery into the drivers side but it doesnt make sense to me as that side is charging at 14v.

 

If you take the truck somewhere to have the batteries load tested, a lot of these so-called technicians try to load test them while they're still cabled together. Insist that they pull one of the ground cables off and test each battery individually.

 

Also you said it sat a week. Is something drawing power just off that battery? Glow plug relay maybe. Worth checking. Usually if they won't start it is the passenger side that is bad.

 

Well I think I got this thing beat. Cut the positive terminal off on the passenger battery, quite a bit of corrosion inside with no way of cleaning it out. Soldered and crimped ring terminals on and got a new "marine" battery terminal that has a stud that I put the three wires onto. Looks like its charging now, and has never turned over so quick!!

Thanks again for the ideas, hopefully this is the end of the troubles.

 

glad to hear you got it fixed mate...

 

I don't know if it matters but the pass side ground attaches to the block. Frame may be rusty

 

Thanks PoolGuy601, my truck was working great charging for a few weeks until today! Same problem, not charging on the passenger side battery and I saw your post. Do you know where on the block this ground goes? I poked around a bit but cannot see where to attach it. I am guessing/hoping/praying this is my problem.

 

do you have a multimeter?