My car's voltage jumps around a lot. It's completely random, so it'll be hard for me to talk about the symptoms, but I'll try. Generally the voltage runs around 13. When all goes as it's supposed to, it stays there. When I turn the ac on or have the blinkers on, there's the small expected drop in voltage, that's no problem. Other times, however, the powerdrain is so great that even something like the turnsignals will cause a 2 volt drop in power, and I know that's not right. It's not only the blinkers, it's any electrical system: Fan, blinkers, ac, stereo, etc. I recently installed a new radiator and battery, but I know that's not the problem because it was doing it before I installed them. And sometimes, just driving down the road my car's voltage will drop not quite into the red, but the first line above it. From there it will slowly flutter back and forth between that voltage and the normal 13-ish reading.

Reving the engine up has no effect; I'm somewhat at a loss as to what to do about this. I understand that some drop is acceptable, but 2 volts for blinkers? That's excessive. The only thing that I can imagine is that there's a short somewhere, perhaps two stripped wires that are coming into contact occasionally.

How would I begin to diagnose something like this?

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89 iroc-z 305 tbi
k&n filtercharger, open element air filter. nuffin' else

 

It sounds like your alternator. Inside the unit there are diodes that convert the AC to DC voltage. Aslo there is a build in requlator to control the output voltage. If these fail then you get a low charge condition. From what you have discribed I would suggest that one of the contacts from the windings of the coil in the alternator has a bad contact. You know where the wires go into alternator at the top? Check those contacts. Spray WD40 on them, this some times cleans the rust of the contacts. Make so the engine is not running

 

Yeah! I completely forgot to mention that. Some idiot that had the car before me (did all sorts of stuff to it) apparently spliced the wrong kind of connector at the top of the alternator. It fits right, but there's an extra wire coming out of it. I need to hurry up and get that replaced... thanks.

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89 iroc-z 305 tbi
k&n filtercharger, open element air filter. nuffin' else