Odd Subaru Forester battery issue

[Donald]

Ok, I left keys in the ignition but off. Opened up hatchback and a little while latter I noticed the tail lights on. Closed the hatchback and lights went off, things looked fine.

Next morning battery was dead.

Tonight I tried a Battery Minder charger and it blinked red light, "rejected, voltage too low".

Then went to an older 10 amp manual battery charger and it cycled on and off pinning the amp meter when it was on. When it was on the vehicle headlights would come half on dim. The light switch was off. Key not in ignition. Door closed.

Pulled the battery cable and am now charging the battery.

I am mystified as to why the headlights were trying to come on. Any ideas??

 

[Chris142]

Electronically controlled cars can do all sorts of weird things when the battery is very low

 

[E150GT]

Yesterday I was working on the car and I noticed the headlights on. I looked and realized I had left the ignition on and the engine off. Battery was drained down to 12.2 volts. Whoops.

 

[HorseThief]

Originally Posted By: Chris142
Electronically controlled cars can do all sorts of weird things when the battery is very low

+1
Aftermarket security systems can make it even more fun....

 

[Chris142]

My wife's Tahoe will lock and unlock it's doors and turn on the radio a few weeks before the battery fails completely....at least it gives a warning.

 

[Donald]

I am not even sure why the battery went dead. Leaving the key in the ignition with key turned to off should not power anything.

This is the 3rd time over 3 years. Its not a battery issue. But who knows, do this a few more times and the battery will be shot.

 

[Trav]

The only way to find out whats going on is to duplicate the conditions and do a current draw test on it to find the offending circuit. Further diagnose from there once you what is causing the draw.

 

[ARCOgraphite]

On a some what side related issue, I go out to my car to get some stuff and the wifes Impreza ( forester did this too) will have a fuel pump running sound from the rear. The thing s running on it own hours after the car was parked and shut off.


The only thing I can guess it a vacuum pump for the PZEV maybe some kind of tank vapour recovery.

 

[WyrTwister]

IF it is the fuel pump , what comes to mind is MAY BE it is actuated by a pressure switch & it is leaking down ? Bringing the fuel pump on ?

I 100% agree , you will never solve this ( except , maybe , by accident ) until you trace down the offending circuit .

A down and dirty hack would , maybe , to install a battery disconnect .