Alternator issues

I bought a 140-amp high-output one-wire alternator from CVF Racing back in March when I bought a serpentine belt system from them.

I installed the Painless wiring kit, put on the alternator, and got nothing. I had to troubleshoot the thing for two or three days trying to get it to work. I added an extra ground wire. I re-did everything twice. Finally, on my last attempt before sending it back, I decided to clock the case around, so it was easier to get to the wires since I was so tired of straining to get them on and off. For some reason, the alternator started working. It was putting out 14.6 volts. I kept checking it just in case, and it seemed to be working great.

In May I dropped the car off to get a new headliner installed, and that ended up taking a very long time. I finally picked the car up on Friday after it had been sitting there for two months and drove it home. Once home, it wouldn’t restart. I charged the battery, did some tests, and the alternator wasn’t working at all. I was only getting battery voltage with the car running. No difference whether I checked at the terminals or straight off the alternator.

I pulled the alternator off the car to check connections, and just because it had worked before, I unbolted the housing and clocked it around a few times. I put it all back together, and suddenly I had 14.6 volts.

Thinking it was fixed, I started it up the next morning to drive over and get my annual safety inspection. However, I was only getting 12.2 volts. The alternator had quit again.

I contacted CVF Racing about an exchange, and they responded that I need to take it to be tested at a local shop, and if I send a photo of the failed test, they’ll start the exchange process.

I took it off the car again, and I took it over to Autozone. It passed the test in their machine twice.

I bring it back home, and stick it back in the car. It’s now charging at 13.3 volts, but when my electric fan kicks on, it drops to 12.9 volts and continues to drop the longer I run the car.

I tried wiring it like a 3-wire alternator and running the R (left terminal) connection on the alternator to the warning light circuit. That does make the charge light on the dash go out, but it didn’t excite the alternator and make it charge.

I tried jumpering both of the terminals to the main power line as suggested on numerous troubleshooting pages to manually excite the alternator. That did nothing. The voltage never moved.

I tried revving the engine up, it goes up a little with the speed, but not much. Revving it up definitely doesn’t excite it.

Am I missing something obvious? Any other troubleshooting tips?

I’m tempted to just go back to O’Reillys and ask for a fail slip from the machine to send to CVF to get the exchange, but after it passed I’m worried that the replacement is going to have the same issues and that it’s something with my setup, not the alternator.

Could a bad cell in the battery somehow cause an alternator not to charge? Any suggestions?

The battery clamps you are running have a well know history of developing high resistance. Get some terminated cables from one of the parts chains and install them. Move you accessories to the battery side of the starter solenoid. Use high quality ring terminals that are properly crimped and soldered.

Will do. I’ll go pick up some cables at lunch and install them tonight.

Well, I took the battery cable advice and went and bought a new set. I moved all the accessories to the solenoid. I cleaned all the ground points. Almost everything went well.

Turns out those Marti Concourse Cable connectors are kind of brittle.

I think the new cables solved my slow crank problem I get when the car is hot, but didn’t change the alternator output at all.

It’s still running at 13.2 volts with no load, then 12.9 with the fan on, then lower and lower.

I think it’s got to be the alternator.

Appears like you might have a bad diode in the Alt. it’s charging but not enough. Maybe just a bad solder connection on one of the diodes and when you disturbed the case it made contact again. Re-solder the joints at the diodes and make sure one doesn’t have a broken lead.

I think you solved the mystery. CVF touts a lifetime warranty, but they were being a bit stingy with it and insisting I eliminate every other possibility before they exchanged it. New alternator is on the way.

I have learned that in the past the auto parts alternator tester wont detect bad diodes. I was having issues with one, had it bench tested and passed. Put it back on the car and it still wasnt charging properly. Took it off the car again and one of the diodes fell out of the alternator. After that experience i simply take the factory units to a local shop and have them rebuilt. Cost a bit more but you wont have any more problems.

Put the new alternator in last night. It’s charging 14.5 volts. It was definitely a bad diode. Thanks for the help.

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