Charging Issue, revisited...., not the Voltage regulator Options

[Aaron Cox]

guys,

im having a heck of a time trying to figure out whats the problem. Gen light came on thursday night on my drive home. i measured voltage goin to the battery as follows:
car off ~13 volts
car idling 14 volts
1500 rpm 15.8 volts BAD

i borrowed a new voltage regulator from bill 'grimstead' and it did not rectify the problem.
all fuses are fine. all connections are solid. the belt is on nice and snug

with the car off, the G light is lit
car idling, it is lit, but very dim....
higher the rpm the less bright the bulb becomes....

now that i have eliminated the voltage reg as a failure mode...
do i have a crapped out alternator?

where is the best place to buy a new alternator?

help me before the WCC... i dont want to blow up my optima....

[ws91420]

The battery is not a load it acts like a capacitor when the car is running. To effectively test any altenator you have to put a load on it. The factory manual states to test an alternator to hook up a VOM, an ammeter, and a variable resistor. Rev the engine to 1400 or 2200 or 6000 rpm. Change varible resistor till you get apporiate amp reading for rpms used. Then measure voltage. 14000 rpm = 10 amp 2200 rpm = 33 amp 6000 rpm = 50 amp This all assuming you still have stock 50 amp alt. Basic electronics you get a drop in voltage after the resistance. If the problem Aaron has described is what I think it is load testing wont do any good either because I tested mine and it did fine at the appropriate rpm but the light was still a problem till I replaced the brushes. This was on my other 914 I was driving till this one was ready and now that alt is on my 76.
BTW the brushes help power the field. the current goes from the outer windings to the diode trio and to the batt post.

Found this about alternators.


Load testing is a standard practice for testing alternators and batteries. Check any service manual of a car that has an alternator.