intermittent low voltage reading

[SiberianDVM]

1984 Carrera. Had North Hollywood speedometer add analog voltmeter to tachometer last winter.

Just had engine/transmission drop done at good race shop for trans rebuild/clutch/and external oil seals. Took forever and just got the car back. The voltmeter sometimes shows normal charging voltage (13.5 or so at 1500rpm), sometimes shows less (11ish). Alternator light functions normally.

Has battery less tha 1 year old.

How do I determine if it's the gauge, the alternator, or the voltage regulator (or a bad connection)?

[Targalid]

Using a separate hand held voltmeter, check at the battery terminals with engine running or at the cigarette lighter while sitting inside the cab. Verify that the two meters are in sync. When running at low indicated voltage, is the alternator light on? It sounds to me like your alternator is charging inconsistently, possibly because of a loose connection or perhaps a problem with the voltage regulator. My charging system ran as you describe until I found and corrected the intermittent loose connection at the 14 pin connector in the engine compartment. It is possible that after your recent engine drop that not all the electrical connections are tight. I found that a plug in voltage meter such as this was helpful:
Amazon.com: INNOVA 3721 Battery and Charging System Monitor: Automotive
Good luck.

[SiberianDVM]

Thanks.

Darn thing won't stay low reading long enough for me to figure it out. This weekend it read low the first time I started it, then normal every other time.

[Chuck.H]

I have an '89 with a autometer analog voltage gauge, and I've found over the last 10+ years that my voltage varies a lot, from the occasional 11 volts to the normal 13.5. Over this time I've had the same alternator and two batteries. I assume my voltage regulator is the culprit, although I guess it could be a connector problem, I'll have to scrutinize them the next time the engine is out.

As long as it's 'mostly' close to 13v, it doesn't bother me or the car enough to do anything about it...

Chuck.H
'89 TurboLookTarga, 380k miles

[SiberianDVM]

Finally got the new Valeo VR from Pelican and I installed it this weekend. Another one of those not too difficult, but incredibly fiddly jobs requiring small hands, good lighting, and the patience of Job.

New VR is similar, but not identical to old Valeo. Kind of disappointed to see that it was made in China.

But it works, and voltage on voltmeter seems to be holding at around 13.5V. Measured at battery terminals with digital VOM and it showed 14.0V.

Taking her to the track this weekend so we will see.