Alternator Overcharges

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Dec 7, 2019 | 12:46 PM

mr-natural

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From: Scottsdale AZ

Alternator Overcharges

L98 engine in 58 Vette w/Delco 12SI alternator. Pin 1 of alternator goes to an incandescent bulb and then to Ignition terminal on the start switch. Pin 2 of alternator goes to +side of battery through the solenoid. The output from alternator goes directly to the ammeter at the dash then to the same terminal on the solenoid as the #2 wire from the alternator. Sometimes the system charges as it should (max amps for a few seconds then settles down to 5 or so amps) however very often the ammeter can be observed slowly climbing until the the needle is pegged. Have not observe the battery boiling when this happens. I used to run with the #1 terminal not connected but that gave the same result. Ideas please.

Last edited by mr-natural; Dec 7, 2019 at 12:46 PM.

Dec 7, 2019 | 05:37 PM

MelWff

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What 12SI alternator are you using stock or perhaps you have a PowerMaster one wire unit since you mention you had a disconnected wire?

Dec 7, 2019 | 06:13 PM

stellar

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From: Pgh. Pa.

It would be good to take a voltage reading when working normal and when guage is pegged. As of now it sounds like a bad voltage regulator in the alternator.

Dec 11, 2019 | 07:05 PM

mr-natural

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MelWff, I lied, it's a 10SI that I purchased through NAPA. For a several years after rebuilding this car II ran with the #1 terminal disconnected. I only a few weeks ago installed the incandescent lamp inline between the #1 terminal and the hot side of the ignition switch.

Dec 11, 2019 | 07:07 PM

mr-natural

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stellar, I'll check voltage output at the alternator tomorrow in relation to the ammeter reading.

Dec 12, 2019 | 01:04 PM

MelWff

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Quote:

Originally Posted by mr-natural

Disconnect the #2 going to the solenoid temporarily and connect a new wire from #2 directly to the alternator output.
See if that makes a difference.

Dec 12, 2019 | 04:13 PM

dplotkin

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Quote:

Originally Posted by mr-natural

however very often the ammeter can be observed slowly climbing until the the needle is pegged. .

The only way to make a properly wired ammeter peg is to run a lot of current through it. Voltage "appears" but current must be "drawn". Alternators self regulate for current, the regulator really deals with voltage. A creeping ammeter sounds odd and should coincide with heat and an acrid odor, but if not you need to examine your wiring and/or your ammeter.

Dan

Last edited by dplotkin; Dec 12, 2019 at 05:05 PM.

Dec 12, 2019 | 05:47 PM

SonnyAK

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From: Southern Illinois

I recently had an overcharging issue on my '66. I initially replaced the regulator with a stock type and had the same issue. Others suggested I try one of the solid state regulators so I gave that a shot and it worked perfectly. Zero idea what the exact issue was, but I haven't had an overcharging issue since. I picked up one of the cigarette lighter digital ammeters to keep a better watch too and that helped with peace of mind that it's working well.