MBMB

Since the last time I used the Speake Spanner (I don't think that caused the problem, but I mention it just in case) on my '89 GT, I've had a persistent small battery drain that leaves me flat if I don't run the car for a couple of days.

Today I narrowed the leak down to the circuit served by fuse 24. Even with all interior lights off, something there is drawing about .47A. (Side question: should that run my battery down so quickly if everything else is functioning properly?)

The 928 Specialists fuse chart has this one listed as "Diagnostic Connector, Current Pulse - Tailgate, Interior lights"

What do I do next to track down the problem?

I don't use my interior lights or tailgate release, and the car seems to run fine with fuse 24 removed.

Thanks,
Mark.

John Speake

hi Mark,
0.47A is certainly a significant "leak" - say 12A/H per day - that's going to run your battery 1/2 flat in 3 days or so.

That current draw represent quite a low resistance 24 ohms or so. And it's 6 watts of power - enough to make something quite warm !

Do both the hazard lights in the edge of the doors work ? Have you tried taking the bulbs out of those in case one is always on ?

Check the wiring diagrams to see everything that hangs off that fuse.

Good luck !

MBMB

Thanks, John. After reading your message, it occurred to me that I may be following a false lead. I didn't make sure the hazard lights in the edge of the doors work, so they might be creating the 6w drain. I'll go back out to the garage in a moment and see.

With that fuse out, the stuff that's still hooked up draws about 0.08A. I was figuring that was the radio clock, digital clock, and always-on sensors. That's not enough to run the battery flat in a couple of days, is it???

What is the "Current Pulse - Tailgate" referred to in the fuse list?

Thanks,
Mark.

FlyingDog

I've heard of the light in the headliner shorting out and killing the battery, so that'd be another thing to check.

MBMB

More data:

I pulled out the hazard light bulbs. The draw with everything off now appears to be 0.2A.

Then after reading Matt's email I dropped the headliner bulb socket out of the headliner to rule out a short there. No change. (Matt, I got my first dog at the Frederick ASPCA.)

But here's something: I'm testing by putting my ammeter between the battery negative terminal and the ground point to which it would ordinarily connect. When I connect the ammeter with fuse #24 out, I get an immediate and steady 0.08A draw.

When I connect the ammeter with fuse #24 IN, I get a 1A draw for about 1.5sec, then a steady 0.2A draw.

Any thoughts?

John Speake

Hi Mark,
If you had all the doors closed, then removing the door hazard bulbs shouldn't have made any difference to the current draw, should it ?

This suggests that maybe the controller that gives the delay on the interior lights after door closure may be the problem. Or mabe one of the "closed door" switches is staying permanently closed.

I don't have detailed experience with this system, and it may be that your alarm systen is also wired into the door closure system.

0.08A is no problem, it would take weeks to drain your battery :-)

MBMB

The rear hatch was open, so the door hazard bulbs were on. All of the other interior lights (that I could find) were switched off. So now with the rear hatch open, all interior lights off, and door hazard bulbs pulled, there's still a 0.12A draw through the #24 fuse circuit.

AO

Make sure the hood light is off. If you place your hand on the hood where the light is, it should feel warm if the light is on. Just a thought.

Bill Ball

Just to be complete, did you pull the glovebox light? 120mA total draw is too high. Less than 50mA is considered normal, although since you mention a clock on the radio, your aftermarket stuff might be raising the baseline draw to the 80mA you mention with fuse 24 out. So, anyway, something is still drawing power of 24.

Fabio421

My thoughts exactly. My annoying battery drain was caused by that little bugger. The switch wasn't working properly so the glove box light stayed on when the glove box was closed. It took a little while to find it but was very easy to fix once I did. Good luck.