Went to harbor freight yesterday and parked the car. Came back out after getting some tools and my battery was dead. Bump started it, and I noticed that my volt gauge was all the way low. None of my lights worked, windows, etc. Went to autozone and had them test my alternator and they said it was bad. Replaced it, and no difference. My pops thought it was the battery, so I took it in and obviously it was low- around 11 volts. They charged it and tested it and said it was good, but my father believes it's still the battery, and that I need a load test done. He thinks that the battery might be defective, and that a standard battery "Charge" test wouldn't catch it. With the battery charged, I plopped it in and drove home. I noticed my volt meter below the standard "13", and whenever I hit the window switch, and it would drop down to about 8 on the meter. Any idea what this is? I plan on taking the battery back within a day or two to have it tested under load.

Back story; never had any problems with this. The last thing I did to my car was last weekend, I installed an aftermarket radio. No bubba wiring, but since I did that, my volt meter read a bit low. Could the harness not the seated properly? I don't know what it could be. Thanks in advance!

-Damon

 

Pops is saying it has a bad cell .. Which makes your pops pretty smart ...

 

does the radio power up with the car on off?

 

So you replaced the alternator, what does the alternator output voltage do at Idle and off idle?
There is a ground wire supposed to be on the alternator.
With a charge on the battery the car should start and if the alternator is working when you hit the lights or window the voltage should Not drop to 8 volts.

 

You can try swapping things one at a time and cleaning every connection or have someone with an A V R tester ( amps , volts, resistance ) check it out and and diagnose the problem .
Any auto repair shop should have one .

Bill

 

What test on the battery was performed if it was not a load test.
That's the only conclusive one I know of.

 

get the battery load tested before you do anything else

 

dar322, yes I can power the radio with the car off, if I cycle the key to the first position I believe. Not if the car is just off.

Noonie, I believe the battery was just charged and tested to see if it holds a charge.

I'm hoping to just check the battery today. I'm hoping that's all it is.

 

Sounds like New Battery time!!!!

 

Definitely new battery time! With a bad cell, you'll still be able to possibly start it after it sits awhile. You'll also be able to operate the radio and blow the horn, but after driving it, the battery voltage will have dropped to lower than you need to restart.
I just had the same thing with my plow truck. After plowing snow for a half hour or so, the plow wouldn't lift anymore. I changed hyd. filters, put on new pump motor, and tested many more areas for problems. Finally took the battery over to NAPA and they did a load test. Sure enough, it had a bad cell. Put in new battery and problem solved.
Duane

 

Defective alternator and battery at the same time?
Do you believe in Santa Clause?

There is no current coming from the alternator, thats the problem.
When the engine runs and your voltmeter shows less then usually,
and if it drops that much when you use the powerwindow it means, that
the alternator does not deliver the current it should.

Search there! If the output of the alternator shows 14V or more, but you can measure only 12 at the battery then the wire between them is broken.
Could be also a loose nut at the starter, where the wires are connected.

If all the current of the alternator would flow into a defective batterie, it would get very hot and spit acid, maybe explode.

 

My vote is for the alternator Either the unit is bad or the wiring to it. Last alternator I installed on my 79 was defective right out of the box. If the alternator is working, you should have 13 or 14 volts with the car running. Can you borrow a known good battery out of another vehicle to prove it one way or the other?

 

bad cell in the battery with car running turn on the lights if it kills the voltage reading its a bad battery ( you really did this hitting the window button)

have the battery load tested

 

About the alternator; he "tested" it in the car with the car running, and hooked it up to the battery. His little reader said that the alternator was bad, which was why I bought a new one. Even with the new one, nothing changed. So do you believe that both my old and new alternator are defective? Otherwise I don't know why their machine was able to charge my battery, but the alternator wouldn't.

 

Thought my battery and alt were defective too... Turned out both were fine, but my gen light on the dash had passed! Without the light, the alt on the later models doesn't get the charge signal. 2ct fix for an otherwise very expensive problem.

 

Before I installed the new radio, there was no bulb in the GEN socket. With the center console out I put all new bulbs in the sockets. It does come on, but it's very dim. The battery/charge problem only started after I did the radio.

 

I think that's a clue.

 

Does the no start only happen while the vehicle is hot after driving? I had an issue last year that after I drive for a while- park the vehicle for about 20 min then go and start the vehicle- it was as if there was no power to the car. I let the car cool down say about an hour or so and the car would start right up. Turned out to be a bad solenoid/starter. Replaced that and everything is ok.

Mine is a 1980 L48 s