Alternator with/without voltage regulator


#1

I have a 95 buick LeSabre with a 3.8 engine and I noticed my headlights going bright and dim and the amp. guage running high. I took my alternator in and had it tested. Nothing wrong. Could their test have detected a faulty voltage regulator inside the alternator?


#2

I will say it should have seen a problem if there was one. One of the tests on a suspected alternator is to see if the output voltage stays within a certain range along with the rated current output.

You didn’t state how much the current is going high. Looking at some basic drawings for your model it shows there is a light module tied to the headlights. There may be a problem with it. First see if the charging circuit is ok in the vehicle and if that checks ok then it would seem there may be a problem with the headlight circuit if the amp gauge shows normal conditions while the lights are off.


#3

The solid state regulators usually fail shorted and cause maximum output from the alternator. This type of problem would not be intermittent.

I suspect a problem in the alternator wiring or a bad ground between the engine and the body.


#4

REMOVE and clean the battery connections. Remove and clean the main engine ground (from the battery) and the chassis ground. If you can’t find a chassis ground, make one. Voltage problems are usually caused by bad grounds in the system, allowing the voltage to “float” at different points in the system…The voltage regulator (inside the alternator) needs a SOLID ground to operate correctly…


#5

While the others may be right, I’ve had the same problem with my Buick. Alternator tested OK. There was a voltage fluctuation causing the bright and dim on the lights. Changed the alternator and problem solved. There seems to be a real problem out there with rebuilt alternators right now so I’d recommend a Delco rebuild if you replace it.


#6

There have ALWAYS been problems with “rebuilt” alternators (and starters). NAPA will sell you a decent one if cleaning up the connections fails to solve the problem.