Weird battery/charging issue

[70jimmy]

Wiring is not my forte'

So after leaving the jimmy sit for about 5 weeks it was dead, No problem trickle charger for a while and it fires up. Run it down the road about 30 miles and around town off and on the next few days and all is well. I did notice a couple times kind of sputtering at low speed or just after shifting, seemed electrical.

Leave it sit for a week, no start, ok same thing. Then leave it sit another week, dead again. Ok I am thinking battery since it starts but then after sitting it doesn't.

Today I hook up the charger on 2 amp and while I am in the garage I hear a click every couple minutes. first one is kinda loud, 2nd one quieter and this keeps happening. So I go over by the truck and notice that the click is from my battery charger and when the loud click happens the guage goes from zero charged to pegging the other side of the guage like overcharged, then on the 2nd click it goes back to zero charge.

So I take the charger off try to start and no dice, it had enough juice to fire the fuel pump but not turn over. So I jump it. Drive it 15 miles shut it off for 10 minutes and its dead again.

So jump it and drive 25 miles and leave it run, then put a volt meter on and its 12.5 volts while running, a guy I know checks out the alternator and says its not charging much and the meter showed 7.5 volts, then he starts looking around and says the old voltage regulator on the core support is hooked up even though your alternator has an internal one. He checks a wire and notices a voltage fluctuation. thinks we need to unhook the old style voltage regulator and get rid of the wiring.

1970 GMC Jimmy
350 TBI from a 93 Suburban
Howell harness and computer with proper chip, been running for 3 years this way.
4 year old optima red top battery

any advice? I have a test light volt meter, ohms etc and some limited knowledge. Planning on having a friend fix it in his shop but figured the more I know the better. Thanks.

 

[Fordum]

OK, where to start?
First, the clicking was probably normal. Your battery is dead, and is trying to draw more than 2 amps. The clicking you are hearing is the circuit breaker in the charger tripping and then resetting.
First thing to try, is disconnect the battery and try the charger again. You might have a short or something in the truck might be overloading the charger.
Also, you need a bigger charger. That one is ok if you have a week or so to charge the battery.
If the alternator is only putting out 12.5 volts above fast idle, let it run for a few minutes, and feel the big red wire on the back of the alt. If its real hot, then the battery may be shorted.

If its a one wire alternator, then all you need to do is hook the one wire to the battery positive terminal.

 

[Greg72]

I'll throw out a couple ideas:

1. Optima batteries don't always charge correctly on a conventional charger. If the needle is swinging wildly back and forth odds are good that the charger isn't actually detecting a load so it's not charging it. A common trick (besides buying an Optima-specific charger) is to hook a second "good" battery to the Optima along with the charger...this will produce enough load to let the charger start working properly. After maybe an hour (at 2A) you can probably pull the good battery away and the Optima will charge normally.

2. Blown rectifier in alternator? Driving around on a dead battery is really hard on the charging system (alternator). If you've been trying to use the alternator as a battery charger...odds are good that you burned the alternator and aren't ever going to maintain a charge with it now. It's probably worth having tested just to be sure....


My best guess is that the battery never got a full charge initially, and all the other symptoms are a result of that.

 

[70jimmy]

Now I disconnected battery cables put charger on 6 amp this time and seems to be charging normally. Before I did that volt meter said I had under 12 volts on battery. I disconnected negative cable and did voltmeter from negative post to negative cable and voltmeter bottomed out, it has a gauge not digital and needle swung all the way left. (Not sure what that was supposed to show??)

Then I used a test light with clip on negative cable and touched negative post, light lit very brightly for a second then went to a dimmer light and held there.

I was told the test light would show a draw on the system???

anyway it goes to the pros on friday to fix me and delete some wiring that should have been dealt with long ago, meanwhile the battery charges so the mechanic doesn't have to waste time charging it.