Strange Electrical Behavior

[SVXalter]

About 2 weeks ago my car wouldn't start and needed a jump. It would only take a jump if everything was turned off. So I got it started and then charged up the battery and got a spare battery just in case. Everything went fine for about a 10-12 days.

Then yesterday after driving around town my ABS light came on randomly (although it was raining and wet outside, which has caused the ABS light to come on before). Then the speakers stopped working, that is the head unit was still indicating that music was playing, but no sound was coming out of the speakers. This continued intermittently.

So I parked the car, and with it still running I turned the headlights on and off. Whenever I turned the headlights on the ABS light would turn on and the head unit would die and then restart. (at this point the speakers were working again) When I turned the headlights off the ABS light would turn off and the head unit and speakers would continue to work.

So I left the car parked overnight and came back today to find there wasn't enough juice left in the battery to start the car. I swapped in the new battery and it fired up with no problem. I tested the headlights to see if it would cause trouble with the ABS light or the head unit and nothing happened. Everything seemed to be working perfectly.

Is something draining my battery? (It was good for about 2 weeks of semi-infrequent use after a fairly quick charge.) This shouldn't cause strange problems while the car is still running should it? Any thoughts would be appreciated.

[Trevor]

Kia ora Dan,

It would appear that you had an intermittent fault which was dropping voltage on several circuits. Turning the headlights on and off would cause an increased battery drain/load and therefore make the fault more obvious.

Reduced voltage could very well have caused the audio problem, as well as ABS fault indication. You report a flat battery with everything OK after replacing the battery.

Everything would indicate a faulty battery, now replaced.

P.S. When changing the battery, could you by any chance have fixed what had been faulty battery connections?

[SoCal LS-L]

Check your grounds..... sounds like a chassis ground is bad or disconnected.

You can also find a parasitic draw by monitoring battery voltage while you pull one fuse at a time..... if the voltage jumps when one is pulled, that circuit is drawing current (of course the key should be off, all interior lights verified off.).