I did a CS alternator upgrade about a year ago, and it's been great. But now occasionally, I'm having some problems with it that I'm looking for help with. When it's working, it's putting out about 14V, as measured by the dash guage. It's roughly accurate, based on past measurements, but I haven't put a meter on it to get an exact reading for this discussion.

At times, the alternator either doesn't turn on, or will stop generating on its own. This has been happening more frequently the last couple weeks. I'm very conscious of my guage, so I pick up on stuff pretty quickly. The first time it happened, I was driving home, and looked down and saw that the guage was reading 12V. I pulled it into the garage and did some poking around...restarted the car a number of times, and was getting no output from the alternator. After poking around and trying a number of things without success, I reconnected the battery, and it was working fine.

A couple days later, while I was out running errands, I started up the car and found the alternator wasn't putting out. I headed for home, but stopped for gas on the way. On a whim, I jiggled the charging wire where it is spliced near the battery. Whether this did anything or not, I don't know, but it was fine then. When the alt is charging, playing with this splice will NOT cause any dropouts in the voltage, so it's not like it's a loose connection.

Last night, I drove to my girlfriend's, a trip of about 10 miles. Alt was fine all the way there, but when I pulled in the driveway and shut off the headlights, I watched the guage drop slowly (over the course of 5-10 seconds) from 14 down to 12 and stay there. I shut the car off and immediately restarted it, and it was putting out 14 volts solid. When I left, it had no problems, and I drove it to work this morning with no problems.

Any suggestions here? My current thought is that there is a problem with the splice in the wire that charges the battery--possibly getting worse when the engine bay heats up a bit. The wire to the alt is original, so not in the *best* condition, and is spliced to a pigtail on the battery--the positive cable was replaced. Could a problem with this wire cause the alternator not to excite? The behavior last night is still a bit weird. Any other suggestions? This is driving me nuts--I'm afraid to drive the car any distance right now for fear I won't make it home.

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Andy Larsen

First thing to check is the drive belt - see if you can turn the alternator pulley by hand (while the engine is off, of course). If you can, tighten / replace the belt. Many mysterious charging problems are caused by slipping belts...

If that's not it, then it's likely that the voltage regulator is defective. That's inside the alternator; repair is to rebuild or replace the alternator with a rebuilt.

Yea,possibly the drive belt or a bad ground, (from the battery to the engine block)or the small ground that comes off the battery.Also disconnect the battery cables and look for corosion on the contact sides.

Thanks guys. The belt was tight, so I went to work on the grounds. cleaned them up with a wire wheel, and so far so good. Put on about 50 miles today with no problems...we'll see if it holds up. Moral of the story is, never overlook grounding.

If the grounds were bad, go over the rest of the alternator wiring and the junction block below C500 as well.

I would replace both battery cables and the braded ground strap just to be safe. The battery cables can look good and still be defective.

See the wire service article in my cave for more things to look at.

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurasic Park)

The Ogre's Fiero Cave (It's also at the top of every forum page...)

Did your charge indicator lamp ever light when the gage read 12 volts? Does it light with the key on before starting?

quote Originally posted by theogre: If the grounds were bad, go over the rest of the alternator wiring and the junction block below C500 as well. I would replace both battery cables and the braded ground strap just to be safe. The battery cables can look good and still be defective. See the wire service article in my cave for more things to look at.

The Pos cable is actually relatively new, but it wouldn't hurt to replace the negative. I did notice the braided ground strap was NOT in the best shape when I was cleaning the end...is this a stock item that I could buy at a parts store?

Thanks for the advice Ogre...I'll take a look at that article.

Your right, I forgot that the 84's use a resistance wire instead of a light. Too bad cause the CS alternator will put a ground on the "L" lead if it senses an internal fault.