intermittant charging on 98 Malibu

My sister in laws malibu has a problem. The charging system stops charging after about 10- 15 minutes.

Ive changed the alternator 4 times and the problem happens with all of them. Battery is also brand new.

After I put the new alt in, it will charge for about 10 minutes or so and then it will stop charging for a little bit and then start again and then eventually it will stop charging altogether.

Is there a voltage regulator on these cars? I know the alternator has a battery connection and then it has another connector with 2 or three wires in it. This usually means that there is an external regulator but where is it? Or is the regulator in the computer?

Does anyone know what signals or voltages are on the smaller 2 wire connector?

Can anybody help?

What is the voltage across the battery when charging, and when not charging? Does the battery go dead? Does the battery light on the dash activate after 10 minutes? I think the regulator is within the alternator.

electrical short most likely

when charging the voltage at the battery is around 14v (a little more maybe) and when not charging, it is around 12.5 or battery voltage. and when it doesnt chargem the battery light does come on in the dash.

Someone told me the voltage regulator was in the computer but I havent verified this yet. This would give meaning to that smaller connector on the alternator.

I was looking for a short but ther intermittant occurance happens as the car is sitting there and I tried moving wires and stuff like that to clear a short but when it doesnt charge, it is pretty solid. it seems like after the elctronics warms up, something quits working.

mainly, I really need to find the voltage regulator. I really doubt its the altenator since it has been swapped with new ones several times now.

anyone have any info on where the voltage get regulated on these cars?

I'll see if I can find out where the regulator is. I do believe that it is in the alt., but its on\off cycle may be controlled by the CPU. [ I can't believe that they would route the actual charging current through the computer, but they could be turning the altinator field ckt on and off using the computer]

...Anyway, I'll hit the library this weekend, they've got some Chilton Manuals there...not all, but some.

I rebuild alternators the regulator is in the alternator. check your fuselink, see on a hand held voltage meter to see if it is charging at the battery also check your body grounds

so, if the regulator is in the alternater, what does that smaller 2 or 3 wire connector on the alternator do? It must have some purpose in and I would expect that it controls the output somehow.

These alternators are not single wire alts which is why I figured the regulator was outside somewhere. but even if it has an internal regulator, those wires go somewhere and do something to it.

thanks for the help.

the smaller wires control the alternator. otherwise it would allways be charging the battery and whatnot. There is a larger output wire but you got to look for it

the wires on the plug are as follows.. p.stator L.light F.fr S.sense