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My battery was 9 years old so I put in a new one. Then the battery light came on so I checked the alternator with a multimeter by probing the pos. And neg. of the battery got 12 plus volts, I put the red probe on the red post on the back of the alternator and grounded the black probe to the alternator case still 12 plus volts so, put in a new alternator, the battery light is still on. I probed the battery and alternator the same way I described above and only get 12 volts. I know I should be getting 13 plus volts. Do you think I got a bad alternator or is there something I'm missing. Car is an 87.
I had a couple of batteries that went bad. We charged them up but no go. I had either an Autozone or NAPA or whatever check the alternator and it was good. Still, the battery was occasionally weak. Charged and tested. They were good. Checked the alternator again and it too was good. Took the alternator to a rebuild shop and they disassembled it and found it had all kinds of issues and need to be rebuilt. Kinda why I don't bother getting it tested. I take it out and have the shop take it apart and see.
Both alternator and battery are new. When car is running the alternator is not putting out more than the battery which makes me wonder if the new alternator is bad.
Both alternator and battery are new. When car is running the alternator is not putting out more than the battery which makes me wonder if the new alternator is bad.
Won't be the first time you get a bad alternator right out of the box. I would say you should take the alternator to a rebuild shop that does it ON SITE so you can see what it looks like if they open it up. Or you can open it yourself and see if anything smells bad but you still have to have their equipment for testing.
Won't be the first time you get a bad alternator right out of the box. I would say you should take the alternator to a rebuild shop that does it ON SITE so you can see what it looks like if they open it up. Or you can open it yourself and see if anything smells bad but you still have to have their equipment for testing.
Thanks, problem is I can't find anyone in town that rebuilds or works on them. Plenty of shops will replace them. I can return the new one for another I was just wondering if there was something I wasn't aware of.
OP - in your particular set of mentioned circumstances you want the electrical "load tested" on the car and evaluated. You can have the battery charged and load tested by itself for confirmation BUT then you need the entire electrical evaluated and load tested "on the car".
Was the alternator a "local" purchase?
Where are you located? Large fleets, municipalities etc all generally have a local "go to" for electrical.
Typically you'd maybe be concerned with an older system to check charging rate at something greater than idle speeds OR actually at idle and then again at higher RPM. Do you know for a fact your meter is accurate? Generally for quick DMM checks I believe most rely on checking "at the battery".
OP - in your particular set of mentioned circumstances you want the electrical "load tested" on the car and evaluated. You can have the battery charged and load tested by itself for confirmation BUT then you need the entire electrical evaluated and load tested "on the car".
Was the alternator a "local" purchase?
Where are you located? Large fleets, municipalities etc all generally have a local "go to" for electrical.
Typically you'd maybe be concerned with an older system to check charging rate at something greater than idle speeds OR actually at idle and then again at higher RPM. Do you know for a fact your meter is accurate? Generally for quick DMM checks I believe most rely on checking "at the battery".
Yes alternator was a local purchase, the meter is new and a good brand ( not harbor freight). I checked at idle and at about 1500 rpms. I checked at the battery and the alternator, never got past 12.6 volts and read the same voltage. Something else, as the car was idling the battery voltage dropped slowly. (I should have mentioned that) which leads me to question the new alternator. I'm returning it Monday and try a new one.
There are 2 fusible links in the alternator/charging circuit. If the old alternator died hard, it may have taken one or both of those with it. Start testing at the alternator with the plug and batt terminals removed. Good luck
Was the failed alternator the original OE/GM or a reman already? If OE/GM maybe you consider the build yourself.
If this car is going to be with you a while and since you're working with a "local" purchase maybe you seize the opportunity to upgrade the CS-130 to a CS-144 which is thought to be a substantially better performer.
You might see if you can put your hands on a carbon-pile load test and actually do the checks that you'll find in the 6D electrical section for a proper check OR use GOOGLE for proper load testing procedures. I've never seen a carbon-pile load tester in a loaner tool program but I've never asked. Maybe the local vendor if they do bench checks has a carbon-pile device and maybe loan. You're his customer.
If you've got a quality meter maybe seize the opportunity to use it to it's fullest and learn how to do the various checks with it. A good Fluke read is maybe this:
I agree with WVZR-1, check with local municipal and trucking company repair facilities to find out who repairs their starters, generators etc. If its available get ahold of your original unit and get it overhauled. I had mine done for about $100 which included anew diode board and shaft bearings. They did a load test and rebuild while I watched; took less than an hour.
If you get yours rebuilt at least you know what you have. Sure beats getting china rebuilt
junk.
I agree with WVZR-1, check with local municipal and trucking company repair facilities to find out who repairs their starters, generators etc. If its available get ahold of your original unit and get it overhauled. I had mine done for about $100 which included anew diode board and shaft bearings. They did a load test and rebuild while I watched; took less than an hour.
If you get yours rebuilt at least you know what you have. Sure beats getting china rebuilt
junk.
I bought a AC delco new from a dealer. I'm going to return/ swap it out tomorrow. My reason for my questions was have I done something wrong. I installed it and I wasn't getting anymore voltage out of it than what the battery was giving. The battery was putting out 12.6 volts and the stud on the back of the alternator was reading the same. I know it should read about 13 plus volts. It doesn't. So I thought, have I done something wrong. I guess I'll know tomorrow.
See is you have 12 volts power at three positions on the alternator with the key in the run position. Large terminal at the rear of the alternator, the large red on the 4 wire connector, and the "L" position, if not it will not charge.
See is you have 12 volts power at three positions on the alternator with the key in the run position. Large terminal at the rear of the alternator, the large red on the 4 wire connector, and the "L" position, if not it will not charge.
St. Jude '03-'04-'05-'06-'07-'08-'09-'10-'11-'12-'13-'14-'15-'16-'17-'18-‘19-'20-'21-'22-'23-'24
If the alt is running properly, you should see 0.5v over batt voltage.
Measure the batt with the key off. Should be 12.5
Measure with the engine running above 1400RPM. Should be 12.5 + 0.5 = 13.0 or greater.
To just say 12v is not granular enough to accurately trouble shoot your problem.
If the alt is running properly, you should see 0.5v over batt voltage.
Measure the batt with the key off. Should be 12.5
Measure with the engine running above 1400RPM. Should be 12.5 + 0.5 = 13.0 or greater.
To just say 12v is not granular enough to accurately trouble shoot your problem.
Yes, I don't get more voltage than the battery. I think I have a bad new alternator.
10-22-2016, 02:11 PM
Another bad alternator?
