Battery Charging Issues

[phillyphils944]

I've got a 1986 944 and I'm having problems with my battery holding a charge. Battery is brand new and the alternator was rebuilt last week. When jumped, the car drives just fine and has a strong charge. When I let it sit for a couple hours and then try to start I get nothing. Something seems like its drawing power while the car is off, and enough power to cause the battery to go dead within a couple hours. Its not my headlamps (made sure they're off), interior lights (never on) or my headlamp motor (needs replacing and is unplugged). Anybody have any helpful advice or had this problem before.....?

[guru944]

phillyphils944:

Bad Ground loop. Current is being drawn even when engine & key is off. Suggest det a digital DMM Volt meter and measure your engine and every Ground point to (-) battery resistance and even your exhaust system (the most common oversight). Next step is to start pulling fuses starting with your radio & accessories circuit. Alarm system & then your Fan Circuit (common power drain when vehicle is hot, Fan stays on and kills battery).

Keep us updated. Later...

[John_AZ]

Originally Posted by phillyphils944

I've got a 1986 944 and I'm having problems with my battery holding a charge. Battery is brand new and the alternator was rebuilt last week. When jumped,....?

If you continue to jump the car, rather than fix the problem.....(repeating...)




Clarks has an electrical discharge page you should read:

Excessive Battery Discharge Rate

And a recent post on common battery drains...
common battery drains, let's have 'em...

J_AZ

[phillyphils944]

Thanks for the heads up John_AZ. I'll get my hands on a volt meterand get right on it guru944... I'll keep you updated. Thanks again.

[mytrplseven]

Listen for the fans after engine shut-down. If they're one, see if they're still on 10 minutes later. That's a quick clue to a bad radiator fan switch. Make sure the engine's warm enough for the fans to come on (leave the A/C off).

[onrails]

just a note: had the same thing, but took longer to kill it. turned out being a bad door jam switch for the dome light was grounding out. just a thought.

[djnolan]

The door jamb switch also controls turning off the DME after shutting the engine off. Once you exit the car and close the door, the dme shuts off. (at least in a late car, not sure abut an early car) If there is a bad door switch the dme will stay energized. easy to test, does the dome light go on and off when you open and close the door?

However dme is not enough to kill a battery in a few hours. I once thought I had a bad alternator draining my battery and had it rebuilt, but I can't be sure if it helped or not. Has anyone else seen a bad alternator drain a battery?

If it is not obvious, the first thing I would do is disconnect the neg battery cable and put a amp meter between the battery and the terminal and measure the drain. Consult Clarkes for more details.