Alternator/Charging Problem - At my wits end!

[Guest flapjack]

Ok guys, I really hope you'll stay with me on this post, because it may be a bit long.

 

I bought my 1975 280Z in November. It had been sitting for about 4 months, and the guy selling it to me had a hard time starting it up. He had just bought a battery a few months back, so he just did an exchange and said it was defective. It started up fine afterwards, and I drove off. It felt it was a good deal at $1200 for the shape it is in.

 

The first thing I noticed was the ammeter. I had never had a car with one in it before. As I made the hour drive back to Goldsboro, it always stayed just about in the middle. Not knowing enough about the gauge I thought "Middle should be good!".

 

It ran fine up until about a couple of weeks ago. I had removed the rear end to do some work on it. With work and the new baby, it was about 3 weeks before I could get it back in. When I did, it started right up and I drove to work. Just as I was pulling into the parking lot at work, the engine died. It started back up, but wouldn't stay running. The battery was dead. I figured it had sat for a while, so I trickled charged it.

 

It barely got me home the next day. So my first thought was the alternator, since I wasn't getting much more than the 12.5v the battery usually puts out. I removed the alternator, took it to the auto part store I frequent, and the test showed only about 10v.

 

I ordered a new alternator. When I got the new one in, the car ran great! For the first time since I've owned it, the wipers were speedy, the lights were bright, and the amps were almost all the way to +60. I was guessing this was how the ammeter was supposed to be reading the whole time.

 

Two days later, on the way to work, the amps were at 0 again. Below 0 if I used the turn signals. It was also kinda jumpy, like there were voltage spikes or something. About halfway to work, the car kinda "clicked" and the radio and engine shut off for a few seconds, then started back up. Luckily, I was able to get to work and back home.

 

I then thought it must be the external voltage regulator. I ordered it, got it installed, and still the 0 amp reading. I removed the alternator, thinking maybe it was a dud, and it wouldn't even complete the bench test... it just made a loud "whirring" noise and decellerated when a load was put on it.

 

This time, I replaced both the alternator and the regulator (again), and am still at 0 amps.

 

I checked every wire I could see. I cleaned the terminals 3 separate times. Everything "seems" fine. But I still get 0 amps, and less even when I run any accessory.

 

A test of the battery showed 12.5v with the car off, and 14.65v with the car running.

 

Any ideas what could be going on???

[spotfitz]

I would first clean every connection you can find. That would include all male and female connections of any terminal, including(especially so) grounds.

Sounds like you have something pulling juice while the car isn't running if you have +12 while running. Start checking the voltage while the battery is hooked up. Once you have a base line, start pulling fuses, while checking the base line with each fuse. Once you have found the fuse that is causing the drain then you have found the problem(maybe one of several). Keep checking until you have run out of fuses and the one time you had the least amount of current is the problem. Once you have found the problem in that circuit then do the test all over again. Again, the least amount of current directs you to the problem area.

Might be a good idea to clean the terminals at the 3 fusible links before attempting any of these tests. Also, check the connections just behind the fusible links, just in front of the battery. These are known to get corrosion build up.

[Pop N Wood]

A test of the battery showed 12.5v with the car off, and 14.65v with the car running.

 

That tells me everything is working as it should. Is the car still dying since you replaced the alternator and voltage regulator together?

 

Ampmeters are horribly inaccurate. A voltmeter will tell you much more. But I guess you have enough experience watching amp meters at this point to know if it is telling you something.

 

A couple of things. You said

 

as I was pulling into the parking lot at work, the engine died. It started back up, but wouldn't stay running. The battery was dead.

 

If the battery died while you were running, it would not have had enough juice to crank the motor. Sounds more like a loose connector or intermittent short to ground.

 

You also said when you replaced the alternator the first time that the "amps were almost all the way to +60". This is extremely bad. Tells me you either had a short some where OR your voltage regulator was bad causing the alternator to put out WAY too much juice. This probably killed the first replacement alternator. You're lucky it didn't fry the battery too.

 

What you are describing since you replaced the alternator and voltage regularo together sounds about normal. If the 75 Z has the same charging circuit as my 70, then the ampmeter movement sound about right. The external voltage regulators are rather crude and don't regulate the voltage as well as new ones. My ampmeter jumps all over when I run the blinkers or any large accessory. It should sit a little on the plus side when it is not moving around, and a little on the negative side could be nothing or it could mean your alternator quit working.

 

You know what this could be? Dirty battery posts (or a bad cable). Believe me I have seen it more than once. Pull the battery cables and wire brush both parts, even if they look clean. Then hook up a voltmeter so you can see it as you drive. As long as the voltmeter shows around 14 volts you should be OK.

 

My worry is you might have some type of intermittent short circuit that is grounding out the altermator causing it to burn up diodes. The problem may have been with your old voltage regulator, but with a 30 year old car you could have a chaffed wire almost anywhere in the car.

 

Good luck.

[Guest flapjack]

Thanks for the replies. Jim, you pointed out some things that I was thinking of myself, such as the 50 or so amps I was getting might have been bad. What should the ammeter be reading during normal operation?

 

I drove it to work today. It stayed almost exactly on zero. When I first started it, it was a bit above 0, but nowhere near the +60 mark like it was with the first alternator!

 

By the time I pulled out of the driveway, it had settled down to about 0. I didn't see very much movement... just enough to let me know it was doing something. I didn't see the usual "bouncing" when I put on the turn signals, which should be a good sign.

 

The only problem now is the wipers are still real slow. At first, I thought it was the motors, but after that first alternator went in, the were moving pretty damn good!

[Guest flapjack]

...by the way, I cleaned the hell out of the terminals, with sand paper and baking soda/water mix.