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I’ve been watching Eric’s videos for years, and I’ve always found answers to my car troubles.
But this time, I’m stumped!I’m working on a friend’s 1980 El Camino. He’s been complaining of it draining all the time.
I tested the voltage while running, and found that it’s not charging.
I then tested the alternator voltage at the alternator (output and ground), and it’s at 0.74 volts!I took the alternator to 2 different auto parts stores for testing. It passed both times.
I reinstalled the alternator, tested again, and it read 0.74 volts again.I’m guessing that this is resistance due to old and crusty wiring? Bad grounds?
There’s lots of places where the ground wire is much more flimsy than the hot wire… could this contribute to the problem?Or am I off track?
I’m really at a loss, so if anyone could help, it’d sure make my day.
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one thing is the alernator has to be engaged for it to work….. that is the data cables going to it….I would first check fuses first and then check the cables for any bad wires…
where are you testing it at,,, most of the time you can pull the boot off of it and tap right where the postive power goes and read it there right on it… by passing a bad cable enless its not entergisingCheck, clean, tighten all battery connections.
Replace any that might cause issues.
Then check the wiring to the alternator and make sure it has a good ground.
Might also check for voltage drop at the starter also check it for partial short to ground.
Not sure if your specific model has a built in regulator or not…
If it is external, check that.Thanks guys.
Yes I’m checking the voltage right at the power output stud on the alternator itself. There’s no rubber boot though.So it’s a bad connection somewhere?
I’ll start at the battery cables.Would that prevent the alternator from outputting voltage at the positive output on the alternator?
That depends on your specific vehicle.
Voltage regulator is one method either internal or external.
Some are ECM controlled.
Best suggestion would be get a wiring diagram for your cars charging system and work from that.It’s a 1980 el camino.
It has an internal voltage regulator. The alternator is less than a year old, and i had it tested twice today. Can I rule that out?I’ll get the wiring diagram online, but my pal has had all kinds of amps and speakers installed. It looks pretty shotty.
Well first I would disconnect all the extras your friend has installed.
There could well be an issue as you stated in the shotty wiring.As to the alternator..
I do not know how it was tested.. what was its output under an extreme load?
It’s possibly to get voltage, but as soon as a load is put on it and it can not output the amps required, the voltage will collapse.As I said, disconnect the extras, check all the connections.
Look for voltages drops and move forward from there with a wiring diagram.[quote=”sotoman3502″ post=171932]… but my pal has had all kinds of amps and speakers installed. It looks pretty shotty.[/quote]
0.7V is the voltage drop of common diodes. IIRC, there was modification in the aftermarket stereo world. It involves using a diode to “trick” the alternator and increase its output voltage.
I got it worked out!
First I disconnected all the extras hooked up to the system.
Then I used my Power probe 4 to check all the grounds and hot wires. I had to redo a few of them
Then I got the wiring diagram and checked connections. Turns out the excite wire wasn’t getting it’s excite command to the alternator. Tested the wire, it’s hot when the key is on.
Turned out to be the pigtail connector on the alternator. I went to the dealership, replaced it.
Now it’s charging!Thanks for all your help guys!
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