Thread: Weird alternator problem

I just recently finished my VE swap and the last thing that's keeping me from driving the car daily is that the alternator is not charging. The alternator that I started off with is from my VE. Here's the sequence of events that I went through:

1) VVLtrain installs alternator on car after motor is installed. Hours later, we start up the car successfully and then notice the brake+battery light is on.

2) Remove VE alternator and install old DET alternator. Car is now being overcharged, with over 15 volts reading on the SAFC and through voltmeter probes in various places (alternator and battery terminals).

3) Remove DET alternator. Go to junkyard, get another alty. Install....almost. Oops, they gave me a 1.6 alternator. Dammit.

4) Bring DET and VE alternator to Pep Boys, who tests both, DET is bad (duh), but VE shows good. Interesting. I refrain from buying a remanned alty and reinstall the VE alternator. Still not charging. ARGH!

5) The next day, I go to a different Pep Boys with my DET alternator. I get a remanned, and have them test both the reman and the DET. As you'd expect, the DET fails again and the reman is good.

6) Install the reman. Its nice and shiny. No charge. WTF!

I've check all power connections, all grounds, any harness that comes remotely close to the alternator connections, the fusible link and any fuse that can possibly be linked to this and everything is ok. I've searched on the forum and can't find a thing.

Help?

That is a strange problem. I would think both of your alternators are bad. Your best bet would be to try a fully working alternator (that you know it works) and see what you get. Some of this Autozone and Pepboys employees are not the brightest people on Earth and possibly did something wrong.

I agree, your alternator should be able to put out a charge whether or not it's hooked up to the car's electronic system. If you can't measure any voltage at the alternator terminals then that's got to be the problem.

They aren't the brightest. But there's not much to testing an alternator. I watched over them and the test machine like a hawk, and everything seemed to be performed correctly.

There is a very miniscule chance that both the VE and reman alternator are no good....but really?? Ugh. I'm tired of removing and reinstalling these things!!

How about your battery?

Get an oem alternator from Fred Casey. Remans are bad news.

I've had a similar problem in the past with my Reman. I replaced the Reman twice and still the same problem. i replaced my batt and it worked fine after that.
Remember, if your batt isn't holding a charge it don't matter how many times you change that Atl.

Why one Atl had you at 15v? that is weird.
Good luck. I will check back on your progress.

If my original alternator was operating at 15volts, I can only assume the voltage regulator on it was defective. Then, it would appear that my JDM OEM alternator is defective, as is my remanufactured unit from Pep Boys. What are the chances?

My battery is fine. Its essentially a brand new Miata battery, and the car starts and runs each time. The voltage on it doesn't dip much below 10v when its cranking, and it sits at a steady 11.5 volts with the car running. It holds at 11.75v with the car off.

I guess my only option at this point is to source yet a 3rd alternator and change it out AGAIN. Basically what this would show is that the alternator testers at two DIFFERENT auto stores are giving erroneous "pass" readings. Hmm.

for how long did you idle or run the car with the 15volt DET alternator ?

About 2 minutes.