My car won't charge the battery at all and somehow it and the alternator tested good at advance auto parts. When I was driving on the highway my voltage went below 10 volts and the radio turned off, then my transmission stopped working so I pulled over and the car was still running so I turned it off and took the battery to advance to charge it to get my car the rest of the way home. When I got the car home the battery was at 13.7 volts. The next morning I started the car and it was at 11.5 volts. I replaced my serpentine belt and checked the ground wires and all are tight. The ground for my subwoofer amplifier was also in good shape. None of my lights are on when the car is off and nothing is plugged in the cigarette lighters. All my fuses are good. My amp wasn't hooked up the night it lost 2 volts. The only light that comes up on the gage cluster is the battery light. I have no clue what to do....please help me

With the car running, whats the voltage at the battery? It should be 12.5 with car off and with car running in the 14's. If it stays at 12 or worse running you need a altenator


"Straight roads are for fast cars, turns are for fast drivers"-Colin McRae

Do you check the voltage on the cable terminals or directly on the battery itself? It happens to me every couple of months and I just unbolt the terminals and shine them up with a file.

Longshot and I don't remember, does our car have fusible links? On one of my chevy's the alt was good, and the battery would have a charge, but the links in between the battery and the alt were partially blown and I could not achieve a satisfactory charge. Not even sure if we have them, my car has been up on blocks for over a year. I would check for continuity between the battery and alternator.


Sig'less since '02!

i have a voltage meter on my radio...my terminals are clean and so is the positive terminal on the alternator. also, i have a lot of miles on my cavy...183,000 give or take a few miles...also after i replaced the serpintine belt when i started up the car the voltage read about 13.6 so i took it for a test drive to see how it was and by the time i got home it was back below 12 volts...before the serpintine belt was changed it was at 11 something.

You could have a short inside the car somewhere draining the battery when the car sits. Do you have an amp for your stereo? If so remove the power cable from it and see if the car still goes dead. Was the alternator on the car when Advance tested it or off the car. If it was off charge the battery and drive the car up there and they can check the whole system (battery,starter,alternator and for an electrical short)....

The amp for my stereo is currently hooked up and it isn't draining the battery while the car sits. The battery drains when the car is running.

Its your alternator. I had the same issue a few years back. I went to a local autoparts store and had my battery and my alternator tested and both came back fine. The battery died again when I got home that same night. I just knew it was the alternator. I had the alternator replaced the very next day and installed the "Big 3" upgrade and I have never had an issue since.

P.S. My battery was a year old optima red top and those things are solid, so I knew it wasn't the battery.

What is the "big 3" upgrade?

could be:
bad battery
bad alternator
parasitic draw


a parastic draw would only kill the battery when the car is off and left for a period of time...overnight. If the car is dying when the engine is running the charging system is at fault.
the 13+ volts you are measuring with the car off is a surface charge on the battery not the true battery voltage. Fully charge the battery,( may take 8hours with a 6amp charger) remove the charger then turn the headlamps on for 15seconds to remove the surface charge. Let the battery recover for 15 seconds then measure the battery voltage. Fully charged voltage is 12.6volts. If the voltage drops the next morning either the battery is bad or there is a parasitic draw. If that is the case report back and i will walk you thru a draw test.

to check the alternator:
Start the car and check voltage at the alternator, it should be approx 13.5 to 15.5 volts with the car running. If thats ok, check voltage at the battery. It should be the same at the battery. If its less, there is a voltage drop in the wiring from the alternator to the battery. if this happens you will need to do a voltage drop test of the insulated and ground circuits.

the remaining option is that the sound system is exceeding the output of the alternator and killing the battery.

Brian Pollert Jr wrote:The amp for my stereo is currently hooked up and it isn't draining the battery while the car sits. The battery drains when the car is running.

Technically if you have a short especially an amplifier it is discharging ALL the time not just when the car is off. It just is more evident when the car is off. Also you didn't answer the part about was the alternator on or off the car when it was tested. An alternator can be good when tested off the car and not get power to the right connections when installed on the car and hence not work.

Brian Pollert Jr wrote:What is the "big 3" upgrade?

Big 3

the alternator was off the car when I got it tested...there hasn't been any battery drain with the car off...only slow draining when its running.

Because the alternator is not charging the battery, get your meter and start doing some simple checks as me and others have said in this post.


"Straight roads are for fast cars, turns are for fast drivers"-Colin McRae

Have you used your cigarette lighter to charge anything? Look inside it for any metal. I have found that my phone charger had a metal ring that came off and stayed inside. It didn't blow a fuse, but it did run my battery down numerous times. It was hot to the touch, so be careful.







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NCR-SCCA

i replaced the alternator and that fixed the problem...the old one was only putting out 11.something volts when it was supposed to put out 14. hope this helps out if someone has this problem in the future. Thanks for the help!!

Good to hear. Brian seriously consider doing the Big 3. It will help keep the alternator 'happy' and its cheap.

having a similar issue, but the car does fine. I deliver meds, and while im running, everything seems fine, the battery is newish. All connections are clean, there is an after-market stereo, but is wired to allow it to shut off with the ignition switch proper. there are fog lights, but are ignition and relay switched. I tested voltage last night and with accessories on (stereo, headlights, Fogs, it tested at 13.98 volts, and with them off at 14.10. is there a possible intermittent problem with this?

sometimes the starter seems to

struggle. Just Checked the voltage and it is at 12.81 after sitting overnight.
sorry about the split post, cant figure out how to edit.

prime M's comment helped me solve my recent issue. My 1996 Cavalier burned up an alternator, the charge output wire was discolored and insulation burned back about 2". I installed a new alternator and within a few minutes of starting the car, the alternator became very hot to the touch. After charging the battery fully, with the car running, I measured a .8V drop between the alternator charge wire (bolt) and the battery positive terminal. After verifying that the battery connection was clean, I traced the charge wire from the alternator to the solenoid (at the starter). FYI, Right before the wire connected to the solenoid, I found a fuseable link. Another wire ran from the same solenoid post to the positive battery connection. I found the connection at the solenoid to be corroded and cleaned it. I also found the connection of the negative wire on the engine block to be corroded and cleaned it. Now, there is only a .1V drop over the positive charge wire and the alternator stays cool.