Alternator Condensor

[Foster48x]

In another thread Car Stereo Issues I had some problems with what I originally thought to be my car head deck wiring. Come to find out after re-wiring the darn thing a half dozen times that it is most likely the voltage regulator on the alternator causing the radio to go into protect mode. I also verified this by testing voltages on other circuits and found it to be spiking at 18+ volts everywhere when the rpm's were up.

I pulled the alternator (it's a 6mo old refurbished Bosch 55 amp w/internal volt reg) and removed the voltage regulator. It looks fairly new but not having the ability to test it I can't tell if it's bad or not by just looking at it. What I did find was the small condenser on the back of the alt looks pretty rough. It looks like its somewhat melted and almost looks like it was repainted black? The metal base that attaches to the alternator casing is really dirty also. I know they half a** these re-builds sometimes so I'm sure it's not new.

Here's a pic




It's my understanding that the condenser is like a resistor that keeps the voltage out of the alternator from producing noise in the stereo system. So my question is, before I buy a new voltage regulator and re-install the alternator, is that all the condenser does? Could a bad one cause any other issues? I wasn't getting any noise from the stereo before the voltage started spiking.

Thanks,
Rick

[carl55]

The condenser is a capacitor that shunts a momentary spike in voltage to ground.
It does look a bit funny. Does a new one cost alot ?

Carl

[Foster48x]

Carl,
From what I've found so far they don't look to be too expensive, maybe $15 or so from a couple of places I found on the net. I couldn't find any of our vendors that carry them. It's going to be around $30 for the voltage regulator so I'd rather not replace the capacitor if I don't have to. However, I also don't wan't to find out later that the capacitor was part of the problem and end up replacing everything a second time.

Rick

[carl55]

Rick
A capacitor can be tested. You can use an ohm meter to see if it is shorted, that would be bad. Radio Shack or any similar electronics store may test it properly. The odds of it being bad are slim.

Carl

[spider2081]

The main filter for the car is the battery. A fully charged battery acts as a nearly perfect filter for an alternator. Any poor connections in the leads at the battery, grounds, or alternator can keep the battery form reaching full charge.
Alternator noise is a whine that changes pitch with the rpm of the engine that one hears in the audio of the radio or sound system. Sometimes one hears the wine after starting the car and then it goes away. That is because the battery may not be fully charged when the car is first started but after driving for half an hour the battery gets fully charged and the whine disappears.
If you are hearing static in the radio that is rpm related it usually is ignition related.
If you have an ohm meter you can check the capacitor as mentioned for shorts. IF it reads a low value of resistance it is defective. If you have an analog ohm meter swapping the meter leads on the capacitor terminals should make the meter read low and then increase as the capacitor charges in the new polarity.
If you have a digital meter it may have a built in capacitor checker.

[Foster48x]

A new voltage regulator on the alt and i'm back on the road. The old condensor seems to be working fine also.

Thanks for all the help guys!
Rick