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Edit: Subject line should be Overcharging.
Had my 32 Ford out for a drive this morning. Just before getting home I started hearing a squeal like a slipping belt within a fairly narrow rpm range. I don't have a tach but could only hear it between about 25 and 40 mph. No squeal at idle. At the same time I noticed the volt meter was pegged above 16 volts. I know it was normal earlier in the drive.
Any suggestions on where to start troubleshooting?
If you have an internal regulated alternator, it's a good bet you need a new alternator.
It's a Chevy 350 engine. Alternator with red, brown and blue wires. Can't see any markings on it. I believe it has an external regulator. There's a black box with Delco-Remy embossed on it. It has blue, yellow and brown wires. On the base it's stamped 515 12V.
Right now with the engine running the dash guage says about 14 and I'm measuring 14.6 at the battery. I wonder if it goes bad when it heats up. One wire inside the regulator is showing some melting of the insulation.
Then I'd suggest taking the alternator in for testing, and replace the regulator.
An easy thing to do is run a separate ground from the battery to the base of the regulator and see if things change. If not, move the ground to the alternator and try again.
If it does make a change then you'll need to clean the ground connections. Easy test and little to no cost.
Finally back to to this project this weekend. Had the alternator tested and it was fine. The ground test seemed to be fine. Put it back together with a new voltage regulator. Took it for a short drive and all was good. Let it idle in the driveway while I watched the ammeter. After about 10 minutes the meter pegged again. I guess the problem is somehow heat or time related and thus didn't show up on the alternator test. When I shut it off the alternator was very hot to the touch, hotter than the valve covers.
I'm ready to just spring for another alternator and voltage regulator to see if that solves the problem. Anything else I could check before that?
Make sure the alternator is properly grounded as well as the regulator.