6V alternator weirdness.

[Simonpie]

This is on a 6V positive ground with an alternator. It has no external voltage regulator. I ASSUME there is a simple solid state one built in. I bought the car like this, so I don't know the source or history of the electrical stuff.

So here's the story. The volt gauge may be a bit off in calibration, so don't harp on the specific number too hard:

When sitting, engine off, battery charged and nothing on, the voltage is 6.5.
When sitting, engine off, lights on, the voltage is 6.3.
When sitting, engine on, light on or off, the voltage is 6.8.

So far so good.

Sometimes, driving down the road with my lights on, I notice the voltage at 5.5. I freak a bit, which doesn't fix it. I tap the gauge. Again, no cure. Why do I like tapping the gauges on old cars? it just seems like something I should be doing. I pull over and start calculating whether or not I can make it to my destination and back without a charging system. I turn off my lights and instantly the voltage jumps to 6.8. I turn on my lights and it stays at 6.8. Problem solved.

So the question is: Do I have a sticky voltage regulator? How long can I use the flick the lights trick before it stops working and I get stuck on the side of the road?

[jax55]

Take a VOM with you and when the voltage drops, verify at the battery.
Could be a bad gage or poor connection.

[Jim/GA]

OK, lots of good info here.

The voltage regulator is solid state and built into the alternator. It can't "stick". It can be going bad, though. Need to have it tested.

Your low voltage with lights on could also be due to:
- the high load of the headlights is slowly overheating your alternator/regulator and output is dropping
- you could have a short in your headlight wiring, causing a very high current draw when those lights are on, pulling the voltage down. Look at your ammeter when lights are on and off, in addition to the voltmeter.

One of the pilots in Top Gun tapped the fuel level indicator on his jet when it was low and flashing red. Very funny.

[SeaSlugs]

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Originally Posted by Jim/TX/GA

OK, lots of good info here.

The voltage regulator is solid state and built into the alternator. It can't "stick". It can be going bad, though. Need to have it tested.

Your low voltage with lights on could also be due to:
- the high load of the headlights is slowly overheating your alternator/regulator and output is dropping
- you could have a short in your headlight wiring, causing a very high current draw when those lights are on, pulling the voltage down. Look at your ammeter when lights are on and off, in addition to the voltmeter.

One of the pilots in Top Gun tapped the fuel level indicator on his jet when it was low and flashing red. Very funny.

yup - btw you can drive for many many miles if not 100+ without a charging system.

also could be poor ground, slipping belt due to high electrical load. also be aware at low idle the alternator isnt spinning enough to have the regulator kick in. so lights on brake on engine running you may suck the voltage down.