I replaced my alternator about 2 wks ago and.

ANONYMOUS

MEMBER
1994 SATURN SL1

I replaced my alternator about 2 wks ago and still have a problem w my battery being drained. My anti-lock light will come on and a small black relay switch under my parking brake (I'm assuming this is what it is by placement and the electrical hook ups) will tick uncontrollably. Soon to follow my battery light will come on. This has been an issue since I got the car. I'm unsure if it's a brake issue or electrical and have had no luck finding a local garage that can find and fix the problem.

1 Reply

CARADIODOC

MECHANIC
33,741 POSTS

Was that a rebuilt or used generator? Start by measuring the battery voltage while the problem is occurring. The engine must be running. You must have between 13.75 and 14.75 volts. If it is low, suspect the generator. If it is okay or even a little high, have the generator professionally load-tested. If it can only develop exactly one third of its rated output current, and "ripple" is very high, it has a defective internal diode. To prevent numerous repeat failures, replace the battery at the same time unless it is less than about two years old. Due to their design, these generators develop huge voltage spikes that can destroy the internal voltage regulator and diodes, and can interfere with computer sensor signals. As the battery ages, it loses its ability to dampen and absorb those spikes.