My 72 164 still has the original SEV alternator....reconditioned somewhere along the way. I find that it puts out about 40 amps at 13.0 Volts with no load, according to my mechanic's test using his VAT machine. However, when a load is applied, the voltage drops, proportional to the load, and can go as low as about 10 volts. For example, headlights switched on result in a reading of about 12 volts. Also the ammeter nearly always shows a negative reading and it, too, becomes more negative directly proportional to the load. He said not to worry about it......just keep driving.

I replaced the fixed voltage regulator with an adjustable one, which I have been told should keep the voltage rock steady regardless of load. Well, no change.....same results.....my test this time. So, either the mechanic is right and I should ignore the readings and just drive, or the alternator should be replaced. All suggestions cheerfully accepted. Thanks