I have a 1970 98LS and this weekend I replaced the alternator and voltage regulator and now I have a dim AMP light. The voltage regulator is another solid-state from Autozone. I already had one on it but the new one has the tall box like the original. The alternator is an AC Delco rebuilt original. I replaced an aftermarket Remy because it was howling at start-up and whirring but the AMP light was not lit before. The new alternator is a little noisier when running than the old one was before its shenanigans. Anyone had this problem? Also of note, every power drawing shows a ground on the alternator but the only thing I've ever had attached to the ground stud is a clip that supports the wiring harness. Should there be a black ground wire somewhere? Thanks for the help.

 

The alternator grounds thru the alternator case to the mounting hardware. No external ground is needed.

The alternator warning light gets its ground thru the regulator. Since you say the alternator is noisy now, and the lamp is dim, I’d suspect a defective diode in your new alternator. If you have a voltmeter, set it to A/C voltage and measure across the battery posts. I don’t remember the specifications for A/C voltage, but I would think more than a few millivolts of A/C voltage would indicate a leaky diode in the rectifier bridge.

 

I'll try that tonight. I hope I didn't get a rebuild that's defective.

 

It wouldn't be the first time. Won't be the last time. 🙂

Did you have to turn in your original as a core? I like getting electrical stuff rebuilt by a local shop if possible. One, to support a local business (or forum member, there's a couple of highly competent rebuilders here) and two I just believe they'll do a better job.

 

I still have the howling one that didn't light the light and the other voltage regulator. I wanted to be sure everything worked before sending the core to RockAuto.

 

Would it hurt to attach external grounds to the alternator and voltage regulator on the odd chance that the case grounds aren't making sufficient contact through the cases/bolts?

 

If there's no auto electric shop nearby, PM "Stellar" here on the forums. He's near Pittsburgh and has been doing auto electric for many years.

For the dinky core charge you'd get by sending it back to RA, invest in a professional quality rebuild.

 

Yeah, but...

The stock Olds mounting bracket only attaches to the front frame of the alternator. That means that the ground path is from the aluminum rear frame, to the iron core of the stator windings, to the front frame. Galvanic corrosion between the aluminum and iron causes resistance in the ground path. This is less of a problem for the external regulator alternators, but the SI family, and especially the CS130, are really sensitive to this. A ground strap from the rear frame to the block is never a bad thing. Evil ex-wife #2 had a W-body Buick GS that would puke the CS130 about every 13 months (the warranty was 12 months). After the third time, I finally found the TSB that said to install the ground strap.

 

Not the alternator ground stud itself?

 

I'm not sure what ground stud you're talking about, but any ground strap that makes electrical contact with the rear half of the alternator is fine.

 

The shop manual shows the two studs on the back as BATT and GRND and the two prong plug for the regulator is between them. Right now the only thing on GRND is a clip holding the harness up in the back.

 

Like this

 

Again, any point on the rear part of the alternator is electrically the same as far as a ground strap is concerned.

 

There should be a star washer on one of the regulator mounting bolts to ensure good ground contact between the regulator housing and the firewall.

 

Which doesn't help with the galvanic corrosion problem if the mounting brackets only bolt to the front half of the alternator.

 

Put the old regulator back on and see if the light goes out. If it does then just change the covers. There has been a rash of faulty solid state regulators over the years.

 

There was not a star washer. I will try a ground strap. If that doesn't work, I'll go in reverse and put the old parts back in.

 

If the light goes out with the alternator unplugged it probably has a leaking diode in the rebuilt unit.

Good luck!!!

 

Turns out it was the alternator. It's on its way back to RockAuto as a Delco warranty exchange. I put the old VR back and the light actually got a little brighter but when I put the old alternator back it went out. Oddly enough the old one stopped howling.

 

Engineers are not supposed to be superstitious. Or, maybe we are supposed to be overly suspicious. Never figured that out, but I have noticed the phenomenon of failing equipment straightening up and flying right after the replacement part arrives, and will often stay that way until you send the replacement back for refund, if you do.

 

Well, hell, of COURSE that's true. The old car never ran better until you put it up for sale or buy a new one.

 

I should add that this is a corollary to the fact that the quickest way to find that tool you lost is to buy a replacement. The old one usually materializes at your feet as soon as you press BUY on the webpage.

 

Any malfunctioning component will work perfectly when demonstrated for the repairman.

 

That’s because equipment/machinery/whatever enjoys making you look like your a liar!!!

 

I have discovered the easiest way to find something is to stop looking for it. Or as you mentioned, buy a replacement.

 

How bout' the one that helps you look for that missing widget and asks..............

"Where is the last place you had it..." Sometime that is followed by a look 🙄 or " If I knew that...."

 

You guys were right, as soon as I shipped the defective one back the old one started howling when cold again. Still no GEN light though.

 

Think Andy Griffith when the freezer broke: "Aunt Bee, just call the man!" and have that unit properly rebuilt.

 

I received the warranty replacement but the old one is still working, I'll get around to it sooner or later. Now my 1991 CC is having rotor warping issues. I swear these cars are jealous women!

 

Warranty replacement works great, the first replacement was defective.