New alternator, still not enough voltage

[colo525i]

Had charging problems after i put in my new lights. So i put in a new voltage regulator, still no increase. Put in a new alternator, still only 13 volts tops with no load. If you add load, say the blower fan or the lights, the voltage drops and doesn't recover. Soon you are running on nearly nothing. Had the auto parts store test the alt. they managed to get 160amps out of it loaded, but at only 13V. Any ideas? i am stuck until i can get this thing rolling.

[632 Regal]

i would venture to say the new alternator is junk. did you need to swap the pully on yours?

they managed to get 160amps out of it loaded, but at only 13V. Any ideas? i am stuck until i can get this thing rolling.

[colo525i]

Yes had to swap old pulley on there. Here's what i don't get though, i have tried 2 supposedly good v-regulators and this new alternator all with the same results. Voltage just drops when loaded. I did try another battery, i got 14v right after starting, but in a few minutes the voltages tanked. Are there any relays that would isolate the load of accessories from the alternator? I guess i don't see how it could put out all the amperage needed but still have such low voltage.

[Ross]

The voltage regulator is bad, buy a new one

[colo525i]

Ross, i didn't make this clear but i tried that with the original alternator. So i have one voltage regulator that has run all of 20 mins and another that was on the rebuilt alternator. Neither v-reg in either alternator makes any appreciable power nor responds to load. Am i dealing with all bad parts here? Possible, but i find it hard to believe all the new parts i received are bad. Am i looking at a bad ground or something goofy like that?

[Ross]

If it tested only 13 v on the bench I can only conclude a bad regulator.
What happens if you disable the new lights you installed??

[etcetera]

When you are testing this in the car, you are probably seeing the battery voltage drop as loads are added. With a fully charged battery and a working alternator on a running car voltage should be up around 14 volts. I think this goes without saying, but never run an alternator without a good battery. They don't like that.

The new alternator only put out 13v on the test stand? Doesn't sound right at all. Does it put out 14+ volts at any load? Probably be bad. Before digging into the car for the problem I'd return the alternator if possible.

It's also possible there is a wiring problem that is damaging the regulator/alternator.

[colo525i]

the bench test got 14.1 out of the alternator. In car w/ a charged battery it will initially read 14.1, but then will drop as any and all loads are added. This can be the radio, the power windows, the blower fan, anything will do it. When tested in car, it would put out 141amps, but at a max of 13 volts. This is why i don't understand it, it puts out enough amperage in the car, but not enough voltage, and enough voltage out of the car, but an unknown amperage. It does this with 2 voltage regulators that are new. I am leaning to some sort of wiring or relay problem unless an alternator with these symptoms could flat out be bad?

[Blitzkrieg Bob]

and your battery cables, if it's all corroded then it will be producing resistance.

[colo525i]

batt cables are clean, the ground strap is a suspect at this point. I'll check it out.