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[Lazslo]

My voltage gauge is fluctuating between normal and fully pegged (red line). Is there any suggestion as to how to test for bad alternator/voltage regulator or bad gauge? It's on my '76 TR-6, and any suggestions would be appreciated.
Thanks,
Laz

[TR3driver]

A digital multimeter is one of those things that every LBC owner should have.  I literally carry one in each Triumph!  If cost is an issue, a cheap unit (under $5 on sale at Harbor Freight) will do.

Set it to a DC volts range that will cover 20 volts; then start checking voltages at various points.  I would probably start at the battery terminals, since overcharging the battery is the biggest concern.  Then check directly at the alternator output (case and big Lucar connector).  If either of those are above about 14.4 volts, then there is a problem with the regulator or the wiring to it.  If both look OK, the final test would be on the terminals of the voltmeter, while it is reading too high.

However, if you need to do something right now and don't have a DMM handy, check the battery cells when the voltmeter reads too high.  If the voltage is really going that high, all of the cells will be bubbling vigorously and the smell of sulfuric acid will be quite apparent.

[Lazslo]

The mechanic has checked via his volt meter and the alternator/voltage regulator seem ok. The pegging of the meter is not constant, but rather it peggs, then returns to normal. Had the TR6 out today, and there was no bubbling or smell apparent. Seems more like a gauge, or connection.  The battery is 5 years old, and could a failing battery cause these symptoms?  Voltmeter suggests that the battery is good however. Time to crawl under the dash to check connections, I guess.
Thanks for your reply.

[TR3driver]

Hmmm, Did the mechanic check the battery voltage _while_ the voltmeter was pegged?

Offhand, I can't think of any wiring fault under the dash that would cause the voltmeter to read too high. A bad battery wouldn't do it either. If the battery & alternator output voltages are OK when the symptoms are occurring, then my next guess would be the voltmeter itself.

FWIW, when I tried to calibrate the voltmeter from my 71 Stag, I discovered that the adjustment was so loose that it would change on it's own.

[douglas foster]

the dark side of Lucas