Bad Alternator?

hivewax · Feb 12, 2006

First, I went to Pep Boys to check the battery. They fully charged the battery, so it's good. Second, I start the car and disconnect the postive terminal and instantly the car dies. I have the original Autolite alternator with rebuilt lettering stamped into it.

And, I just got the car back from the body shop to install the side scoops. After that point, the AutoSound Kenwood 801 stereo doesn't work, but lights up, and the now the charging problem. They had issues starting the car, so I think maybe they switched terminals on the battery and blew the alternator since the car when bought has black going to positive and red going to negative. I'm scared they also killed the new stereo.

Any feedback is appreciated.

Tim65GT · Feb 12, 2006

Remove the battery and charge it.

Hook it up correctly, and see if it starts.

Check the charging voltage while running with a meter, don't disconnect a battery while running.

If it's less than 13 volts, the alternator is not charging.

Have it tested. If good, It's probably the regulator.

Once you get your alt charging, then worry about the radio, It's a separate issue.

66nightMARE · Feb 12, 2006

Id say its the voltage regulator. Sounds like a similar problem I had.

jdowen2 · Feb 12, 2006

"They had issues starting the car". Maybe they put the jumper cables on wrong. If they did indeed put the battery cables on the wrong terminals they need to fix whatever they fried.

latamud · Feb 12, 2006

Take your alt to Pep Boys and have them test it. If it is good you probably have a bad rgulator.
The stereo should have a fuse. But, if it lights up it might not be blown. Or there's not enough juice to sustain it.

LUCAFU1 · Feb 12, 2006

do you have a muliti meter? check the voltage comming out the altenator. go from there.

hivewax · Feb 15, 2006

thanks everybody,

i took out the alternator and will have it tested after work tonight at a parts store. the wiring was covered in oil and i pulled off the pigtail connection... the middle ground connector of the pigtail snapped off (!) i'm guessing. it looked corroded. i did have coolant leaking from the upper hose. can i replace the pigtail connections or do i have to buy the whole wiring harness for that area?

hivewax · Feb 17, 2006

how do you use the multimeter to check if the voltage regulator is good? i have one of those STANDARD electronic regulators which was installed a few months ago.

battery read around 12.93 volts after trickle charge. then, started the car and waited 10 minutes. at 2000 rpm and headlights on, the battery read around 12.53 volts.

dennis112 · Feb 18, 2006

hivewax said:
how do you use the multimeter to check if the voltage regulator is good? i have one of those STANDARD electronic regulators which was installed a few months ago.

battery read around 12.93 volts after trickle charge. then, started the car and waited 10 minutes. at 2000 rpm and headlights on, the battery read around 12.53 volts.

Doubt you can do anything with the multimeter at the regulator, except measure voltage from the alternator.

Everything points to the alternator (or regulator). The alternator is not charging by the fact that you cannot run with a cable removed and the low voltage you have when the car is running. You should get around 14 volts when running.

You can check your charging system at home by running a jumper between a couple of terminals of the regulator plug. I don't remember which 2 treminals (terminal 1 and terminal 3??) but I am sure someone will chime in soon. That totally by-passes the regulator and makes the alternator charge full time. You can then measure the voltage at the battery--should be around 14 volts. If the alternator charges, then the regulator would be bad.

You need to get your alternator tested, which I know you plan on doing. Voltage regulators are cheap so if your alternator tests good, plan on getting another one. It being electronic, it could be toast if hooked up backwards. Of course your wiring has to be up to snuff too.

Damage to the stereo is possible. A long time ago Kmart replaced a battery in my GM truck and crossed the wires. It took a power transistor out of the stereo.

WORTH · Feb 18, 2006

dennis112 said:
Doubt you can do anything with the multimeter at the regulator, except measure voltage from the alternator.

Everything points to the alternator (or regulator). The alternator is not charging by the fact that you cannot run with a cable removed and the low voltage you have when the car is running. You should get around 14 volts when running.

You can check your charging system at home by running a jumper between a couple of terminals on it. I don't remember which 2 treminals (terminal 1 and terminal 2??) but I am sure someone will chime in soon. That totally by-passes the regulator and makes the alternator charge full time. You can then measure the voltage at the battery--should be around 14 volts. If the alternator charges, then the regulator would be bad.

You need to get your alternator tested, which I know you plan on doing. Voltage regulators are cheap so if your alternator tests good, plan on getting another one. It being electronic, it could be toast if hooked up backwards. Of course your wiring has to be up to snuff too.

Damage to the stereo is possible. A long time ago Kmart replaced a battery in my GM truck and crossed the wires. It took a power transistor out of the stereo.

Chining in , if you jump the "B" terminal with the "F" terminal on the regulator it will go to full charge. sometimes the "B+" terminal is marked "A"

before you do that, replace the wire lug you broke off, and make sure the regulator is grounded good, it grounds threw the mounting screws, so make sure they are clean and tight, use a larger screw if it's loose.

hivewax · Feb 18, 2006

thanx for the tips. i bought a new Palladium rebuilt Autolite w/ lifetime warranty. they spun the old one by hand and heard clicking in the case and said it was bad. i also took the car into a local vintage mustang shop and they said there's a short in the wiring harness that goes under the radiator support (sparks were flying). so, i had them get another electronic regulator, engine and alternator harness. the shop will also do the installation. i wish i could of done it myself to save some dough, but this is all new to me. and, i don't want to blow anything up!

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