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lsversaw · 03-29-2017, 03:28 PM

Somebody please correct me if I'm wrong, but I think that the only thing that can cause voltage drop between the alt and battery, at any rpm and load, is resistance in the wiring (including connectors) between the two. To me, a drop of 0.4 volts sounds a little high, but instead of worrying about the difference, I would first measure voltage from the battery + post -- NOT the connector on the cable -- to ground at starterman99's 1500-2000 rpm. If that voltage is at least 14.1 (some might say 14.2 or 14.3), then everything in the charging system is working: alt, voltage regulator, wiring, connectors and terminals, even the belts. It would be nice, but not necessary, to see that much voltage at idle. It's necessary to see that much voltage with everything turned on and at above-idle rpm, if your alternator output is enough to run all the loads at once. Which it should be.

03-29-2017, 03:28 PM	#28
lsversaw Registered User Join Date: Aug 2013 Location: McPherson, KS Posts: 86	Re: Alternator Somebody please correct me if I'm wrong, but I think that the only thing that can cause voltage drop between the alt and battery, at any rpm and load, is resistance in the wiring (including connectors) between the two. To me, a drop of 0.4 volts sounds a little high, but instead of worrying about the difference, I would first measure voltage from the battery + post -- NOT the connector on the cable -- to ground at starterman99's 1500-2000 rpm. If that voltage is at least 14.1 (some might say 14.2 or 14.3), then everything in the charging system is working: alt, voltage regulator, wiring, connectors and terminals, even the belts. It would be nice, but not necessary, to see that much voltage at idle. It's necessary to see that much voltage with everything turned on and at above-idle rpm, if your alternator output is enough to run all the loads at once. Which it should be. __________________ Scott 1972 C20 long-wide. 350/350, Cheyenne Super, wood bed, PS, PB, dual batteries, dual tanks, leaf springs, gauges. No significant rust. No significant paint. 1971 C10 short step. Originally a 250/3ott with no options, now a 350/4L80. I purchased it already restored; only needs about 300 little details fixed.