Problems with voltage/alternator?

[Glockycharms]

Hi guys,

I have a problem with my 1990 Toyota pickup concerning the above mentioned subject.

every once in a while the brake light oil light comes while driving and then will go out after a few minutes.

I placed one of those voltage meters that go in the lighter plug to monitor the voltage and low and be hold, when these lights come on my voltage drops to 12.2-12.1.

The voltage goes back up to 13.7 - 13.9 after a few minutes 5-15 and then it won't do it again for days.

I realize the car is old so i wanted to know if you think it is the alternator/regulator on it's way out or maybe a wiring problem?

Battery is fairly new and voltage is good, i charge it at home when i get back to make sure it is fuly charged but battery is holding charge.

 

[Quest]

Do the following check:

-load test your battery with a carbon pile tester (capable of 200A) and see how well your new battery is. When in doubt, bring it in for an exchange for a fresh, new, good one.

-check all your connectors from your wiring loom. There shouldn't be any reason why your oil light would come on unless you have intermittent connectivity problems. Afterall: if your engine is spinning and your oil pump is pumping happily along the way, oil light should stay off always.

-Because of that suspicion, check your chassis to battery grounding, wiring loom to ground,alternator to ground, all meters to ground, instrumentation cluster to ground,etc. IF you see something bad/corroded brokent, fix it.
(chassis, wiring loom).

Lastly, load test your generator with a carbon pile tester while your engine is running+battery charging. With 200A load, the engine should come to a quick stall and when you disable the load, your battery charge reading should jump right up to approx. 14v or around that (you live in FLa, right?)

There is no reason called "intermittent" unless the history of the truck is unknown (wiring, grounding, instrumentation cluster, engine side of the wiring, etc. been tempered with, or in a collision, or it's was a flood out car before). As for alternator, it's either a dud or good. Regulator is built right in to the alternator so if it acts intermittently, it will act intermittently under that relative window on a consistent basis. To fix it is to replace the unit.

Also: install a small aftermarket voltmeter to monitor your voltage.

 

[tom slick]

more then likely it's the brushes. they are $15 and easy to change once you have the alternator out.

 

[Donald]

I'd pull the alternator and bring it to a place that rebuilds them and have them test it. While it could be brushes it could be something else. Even if its brushes, in some cases they turn the stator (??) on a lathe and make the area contacted by the brushes smooth.

I suspect its a loose or corroded wire or connection.

 

[Glockycharms]

i have always wanted to upgrade the alternator, it only puts out like 60-70 amps.