porschejim928

For a while now my car has had a battery drain when just sitting. I'm trying to test the drain now. Putting my meter between the disconnected negative battery cable and the negative battery post I am getting these numbers:
1.3 amps with light in trunk on(light by windshield not working).
.09 amps with light off.

How bad is .09 amps? What is normal?

86.5 928

j.kenzie@sbcglobal.net

0.09 amps = 90 miliamps.
Normal, depending on equipment like radio, alarms, etc. would be 30 miliamps.
90 is not bad, it could be something quite subtle.
Good luck,
Dave

Kiln_Red

You can disconnect the passenger door so that you may pull fuses as you watch your meter. If the draw is on a fuse protected circuit, then this will isolate where to trace.

You may well kill the draw by disconnecting the passenger door as the door pin switches are a source of current draws quite often.

FredR

When I do this check [not very often] I do it with the door locked and thus the alarm armed to get the correct ampage number.

At 90mA I would be looking for the leakage. One approach is to look for a relay that is a bit warmer than the others first thing in the morning and of course you can pull fuses to see if you can spot the leakage circuit.

I had a problem of this nature years ago on my late S4- eventually the problem was traced to a minor short in the tailgate wiring that was chaffed and a cable was leaking to earth.

Regards

Fred

porschejim928

I removed the fuse for the interior lights and it didn't make a difference. Can I assume from that it is not the door switches?

porschejim928

Anyone care to guess what fuses I should try first?

Darien

Do you have an external stereo AMP / Bass Speaker?

I would start at one end and test across the board.

porschejim928

I'm reading through some other threads and someone suggested an IR gun. Will that really work?

porschejim928

I had one but I disconnected and removed it.

dr bob

IR gun is useful for relays but seldom for fuses.

I have a few tools that help for this stuff. One is a small 12V bulb wired through a fuse housing. You can do similar with narrowed male spade terminals but most are a little thicker than fuse blades. Anyway, plugged in to a fuse socket in place of the fuse, it glows when current passes through.

Harbor Freight sells a little digital ammeter with 30A capacity that plugs into a fuse socket. Handy. I made a set of pigtails for it using a fuse holder, some 12ga wire and a couple test clamps (small battery charger clamps). Connect the pigtails in series with battery ground to watch total current flowing from the battery.

Fuses have a small amount of resistance. So if any current is flowing through a fuse, there will be a measurable voltage drop across the fuse. Use your DC Voltmeter function and needle probes to poke through the little openings on the back of each fuse. A voltage reading will tell you that current is flowing. This much faster for a first pass test than removing each fuse one by one and testing current flow directly in series.

Plus the ammeter you are using, knowing it typically has a 10A max capacity.

Alan

No it could still be partly the interior lights. The relay itself is supplied on fuse #6 - the lights only are fuse #24 (labelled for this).

It is best to just be systematic & diligent when chasing down parasitic leakage - however it is most likely to be fuses #17 - #29 that are at risk (on this year) since they are all permanently supplied while the others are switched (varies greatly by model year).

Alan

porschejim928

Just wanted to share some of my findings. I'm not sure if my first .09 was accurate. I got that when the fuse for the interior lights was still in, but I was holding down the button for the trunk. Since removing the fuse I've been getting .12. I've been using this as my guide to the fuses:
https://www.928gt.com/t-8586fuse.aspx

I noticed that I have #3 and #22 fuses in. The #3 is a 15A and #22 is a 3A. Any idea what these would be doing? When I removed the #3 I went down to a .09 so that might be part of my problem. Removing the #22 didn't seem to make any difference.

I maintained a .12 when I removed the #6. The #24 has been out for all the tests.

I'm pretty sure my battery is trashed from this drain. With the negative disconnected it went down from a 12.4 to a 12.3 overnight. Shame it was only like 3 years old. Light to figure this issue out before I get a new one.

upstate bob

how much does the clock draw (early models)?

dredpyrt

I had the same issue with virtually the same voltage drops. Turned out to be the relay for the interior lights.

Alan

Try this.

Alan