Alternator Overcharge

[Dan A.]

The restoration battery in my 72 LT-1 was getting long in the tooth so I ordered a new one, which as has been discussed is probably a 6 month wait. In the meantime I bought a Walmart battery to tide me over. It works great, but on two occasions (out of probably 10 or 12) the battery boiled over after a 10 mile drive. I put the old battery back in, which was still functional, and checked the voltage. When I got home from my usual drive it was showing right at 14 volts at idle. I checked it again this morning after letting it sit all night and at fast idle I got a reading of 14.68 volts, which seems high. All connections and wires are clean and appear to be in good shape. Assuming the (original) alternator is over charging can a good local shop handle the repair or should I find a shop that specializes in these old units? I guess another alternative is to try and fix it myself which I wouldn’t mind tackling if I could find the parts.

Thanks

[Dan A.]

Re: Alternator Overcharge

Thanks, Dave. If in fact I have an issue I would prefer to fix it myself. This is very helpful.

[Joe L.]

Re: Alternator Overcharge

The restoration battery in my 72 LT-1 was getting long in the tooth so I ordered a new one, which as has been discussed is probably a 6 month wait. In the meantime I bought a Walmart battery to tide me over. It works great, but on two occasions (out of probably 10 or 12) the battery boiled over after a 10 mile drive. I put the old battery back in, which was still functional, and checked the voltage. When I got home from my usual drive it was showing right at 14 volts at idle. I checked it again this morning after letting it sit all night and at fast idle I got a reading of 14.68 volts, which seems high. All connections and wires are clean and appear to be in good shape. Assuming the (original) alternator is over charging can a good local shop handle the repair or should I find a shop that specializes in these old units? I guess another alternative is to try and fix it myself which I wouldn’t mind tackling if I could find the parts.

Thanks

Dan------

All 1971 Corvettes originally used a Delcotron series 10SI.

If your car has its original alternator, including original split ring (rear) case half, the last available GM parts for that alternator are as follows. However, all are GM discontinued except for the regulator which is still available:

rectifier/diode bridge--------GM #1867531

diode trio---------------------GM #1985348

brush holder------------------GM #1984462

regulator----------------------GM #1116423

Of course, all of the components are available in the aftermarket if you so choose.

[Duke W.]

Re: Alternator Overcharge

Make sure the two terminals from the harness firmly grasp the regulator spades.

My Cosworth Vega developed an intermittent overcharge problem that took me some time to diagnose. To make a long story short, the culprit was a worn regulator spade that didn't allow one of the wires to have a strong grip on the spade.

The cause of the wear was likely the four-cylinder engine's second order vertical unbalanced shaking force that generates a +/- 15g/233 Hz peak vibration at 7000 revs and 5000-7000 miles hot lapping Riverside and Willow Springs back in the 80s and 90s.

Cruciform crank V8s have all first and second order shaking forces and rocking couples balanced, so regulator spade wear may not be an issue, but you very likely need a new regulator and you may as well replace the brushes, too and clean and regrease the rear bearing. It's easy to disassemble the alternator to replace those parts. The procedure is in your COM.

Be aware that one off those wires in the side connector is always hot, so disconnect the battery when you do the work.

Duke

[Dan A.]

Re: Alternator Overcharge

Thanks, Joe & Duke. Your input is always appreciated.