'97 truck - alternator ? battery indicator light double check me here

[schiker]

What is the battery symbol indicator suppose to do? I thought it indicates the alternator is not charging. Its wired to battery pos. then grounds through the alternator in line. If the alternator is charging the voltage potential from the alternator "breaks" ground and the light goes out. There is a diode that keeps the alternator from pushing current through the light backwards giving a false indication of not charging.


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I have left my siruis radio on 2 maybe 3 times over the last month and drained the batteries down and had to boost to to crank up. So batteries are suspect to begin with.........

So drove to school this AM the truck cranked and ran fine. I did not see voltage gauge low but could have missed it easily. Did not see battery indicator light either. Never have I seen it stay on past bulb check lighting. Came back to truck 3-1/2 hours later batteries dead. Get jump and voltage indicator reads low. But battery symbol light went out pretty quick. Feel battery connection and they are loose. Try to nip up passenger side pos post and it strips. Uhhgg.

So I go to Wally world and lock doors and leave truck running. I get two new batteries.

Driving home the voltage guage reads low and climbs a little braking but never gets back to 14 V normal (passenger side Pos. post loose). At home I do the side post upgrade with stud and nuts. I cut off rubber and flattened terminal ends and cleaned them with wire wheel. Should be nice and tight and clean.

When I crank up it zips over but battery light delays cutting off maybe 5 second. First I have seen it do this. Drive it a little while and voltage reads 11-12 volts doesn't climb to 14 v but battery symbol light is off.

So I go back to Walmart to check batteries out since my battery symbol is not on.

They check 1. battery 12.62V 740CCA (Good) , 2nd battery 12.50 805CCA (Good)

Together ? 12.57V 1148 CCA (Good)

Starter Test Voltage 11.00V 1.23 Seconds

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Charging system Test Results - LOW Voltage

No load 12.47V Loaded 12.28V

56mv Ripple ....Charging system problem

Check belts, connection, and grounds. Alternator service recommended if connections are ok.

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When I was leaving Walmart the battery light stayed on for 10-15 seconds The longest I have ever seen it stay on but it does go off.

I take it might Alternator has given up but is putting out just a little. Just enough potential to cut the battery symbol off but not enough to charge the batteries.

I guess I probably killed it driving with way loose positive post connection on passenger side. The alternator may have tried to jump in and out and burnt out the voltage regulator

Grounds I have extra passenger side I run a second wire to back of intake and on drivers side I run another one to the fender. These are in additon to the factory grounds that run to intake on drivers side and fender on passenger.

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Do you concure its 99.5% probably the alternator is bad but why does the battery light go off. I guess the alternator has to more completely die for the battery symbol to come on and stay on ?????? But 12.5 ish volts at battery to 12.47-12.28V at alternator gives 56mv positve charge avg turning light off but not enough to charge batteries to normal 13.8 ish volts. ie Alternator is suppose to have 14 + volts.

 

[ak diesel driver]

probably fried the diodes or regualtor when boosting

 

[Bernie]

Yep, you probably blew a diode pack in the alternator. Might have been from boosting, might have been from the lose positve. My money would be on the loose positive as being the cause. Either way though, you need an alternator.

On the plus side, now is the perfect time to upgrade that stock 100 amp unit you probably have. There's a 140 amp unit that will fit but you'll need a longer belt (bigger case) and an adapter for the field connections. (Adapter is about $15 in various places online)

 

[schiker]

Yeah, apparently it was the alternator. I just put a carquest rebuilt unit on it.

I have never really had the battery symbol idiot light tell me much on an automobile. I guess unless if you count when it delays cutting off and you remember to watch the voltage meter. Kinda like a check guages light.

Anyway fixed it. Feel better about the battery connections now. I bet it was the passenger side pos post that caused the issue. I usually boost from driver's side just to help dampen the surges to alternator (in my mind but probably not really). As the alternator attaches directly to the passenger side. This past jump I went to passenger side and drove with a loose connection which probably allowed a marginal connection to vary voltage considerably to the alternator.

 

[Bernie]

If you check your owners manual you'll see that GM says to only boost from the driver's side, for this particular reason.

Boosting on the passenger side puts too much of a load on the alternator and doesn't allow the driver's side battery to help out.