My 91 with 126 K miles has a problem with the electrical system. Volt meter on the dash wanders on the high side. I have put a voltmeter across the battery with the engine running and read 14.5 to 15.5 with a steady frequency. Engine off, battery reads 12.97 volts. Checked the alt at Autozone on and off the car and its okay, replaced the voltage regulator just to be sure and it still wanders. Any ideas? Thanks, Paul.
Reading your post brings to mine the age-old adage: if it ain't broke, don't fix it. The voltage meter is probably out of calibration, but as long as it shows a positive charging action, I'd not mess with it further. The factory supplied guages aren't all that precise. Of course you could always bring it in and get the existing guage re-calibrated or purchase a better 'after-market' guage.
Hope this is of some help......
Dave S(Texas)
That is a high voltage reading, 14.5 should be around the max. I hesitate to tell you it is the alternator, but I would have replaced them as a set.
15.5 volts is too high, the fact that it cycles between there and 14.5 possibly suggests that there is a diode problem.
Connect your VOM between the alternator output stud and battery negative, set the meter to AC volts, start the engine, if the AC voltage (ripple test) is near or above 100mv, there is a diode problem.
Parts store diagnostics are iffy at best.
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