ANOTHER parasitic battery drain problem

[Lewis Long]

I've been through past threads, watched YouTube videos, and talked to friends, with no luck.

Car: 1998 Boxster, ~110k miles, 5 speed, no heated seats or alarm.

The battery drain completely drains a brand new, fully charged battery in two days. (I have replaced the battery.) The multimeter reads at 12.83 volts, so the battery is healthy.

A multimeter between the negative post and ground, with all accessory lights (front and back boot, door markers, overhead) off, shows the car drawing about 3.5 amps. Two different multimeters gave the same reading. Based on available data, it should be drawing from 70 mA down to 30 mA after the ignition is turned off.

I have pulled each fuse to locate the offending circuit, but with no effect; the draw stays constant. I do have a aftermarket stereo with two external amps, but I disconnected both amps for the test; no change. The head unit is on the existing fused circuit.

What am I missing? Is there a separate set of fuses, breakers, or relays not run through the primary fuse box in the driver-side footwell?

Any help or suggestions will be much appreciated.

[Phat Hippy]

Lewis, I would unplug the ignition switch under dash and check the amperage draw again. The switch is a constant cause of electrical problems. There are also a set of relays (fuses too?) in the trunk (not frunk). I hate electrical gremlins... Good luck I hope you find it. If it is the switch, replace it with the best quality OEM part you can find.

[thstone]

My first thought is to further investigate the aftermarket stereo. I would track down/trace the power wires for every component in the stereo system.

The installer may have connected the stereo (I use this word generically to mean any or all of the actual components) direct to the battery or to a wire that connects direct to battery power without going through the stock fuse panel in the driver footwell. If this is the case (and the installer knew what he was doing), then there is likely another fuse block or inline fuse for the stereo power that is in parallel with the stock fuse panel.

[Lewis Long]

Originally Posted by Phat Hippy

Lewis, I would unplug the ignition switch under dash and check the amperage draw again. The switch is a constant cause of electrical problems. There are also a set of relays (fuses too?) in the trunk (not frunk). I hate electrical gremlins... Good luck I hope you find it. If it is the switch, replace it with the best quality OEM part you can find.

Thanks for the suggestion. It is helpful, and I appreciate it.

I have ordered a new ignition switch, and am awaiting its delivery, but it didn't occur to me to simply unplug the existing switch and check the current draw. I will do that while I wait for the new part.

If it's not the problem, at least I will know where not to look, and will have a backup switch when it eventually does fail.

[Lewis Long]

Originally Posted by thstone

My first thought is to further investigate the aftermarket stereo. I would track down/trace the power wires for every component in the stereo system.

The installer may have connected the stereo (I use this word generically to mean any or all of the actual components) direct to the battery or to a wire that connects direct to battery power without going through the stock fuse panel in the driver footwell. If this is the case (and the installer knew what he was doing), then there is likely another fuse block or inline fuse for the stereo power that is in parallel with the stock fuse panel.

Thank you for the suggestion. You have given me an idea for another area to investigate.

I installed the aftermarket stereo myself. I have a lot of stereo installation experience, and I don't trust an aftermarket installer to wire it correctly, avoid shortcuts, or make sure that there are no squeaks and rattles under the dash. I am very detail oriented, and even a competent installer isn't working on their own car, and won't have to live day-to-day with the results of a shoddy job.

I was very careful to wire the head unit into the existing wiring harness, and preserve the appropriate wire/fuse assignments. I was also careful to route the wiring, and protect it with split loom from crimps or wear. I did pull the head unit when the problem started to make sure that I didn't pinch or short any wires, and that nothing pulled free from a connector. Having said that, however, I neglected to pull the stereo and THEN check the current draw with it out, which I will do today.

Thanks for the suggestion, and the idea. This is a very likely place to look for a problem.

[Lewis Long]

Thanks for the suggestions. After reading Phat Hippy's post, I pulled the plug from the ignition switch, with no change to the current draw. On the good side, I do now have an extra ignition switch for when this one fails, and have learned that I can seek a new career as a contortionist, after wedging my 6'4" body into the footwell, upside down.

Thstone, I installed the stereo myself. I have a lot of stereo installation experience dating back forty years (!), and I don't trust aftermarket installers working on someone else's car to make sure that there are no shorts, rattles or squeaks after the installation. I made sure that all of the lose wires were in split loom, capped and tied up. It is wired into the existing wiring harness with an aftermarket adapter plug from Crutchfield, and fused from the car's fuse block, and no power drawn directly from the battery, so pulling fuses should have isolated that problem. The amps do draw directly from the battery, but I pulled the amp power lines to test the draw.

That having been said, though, your suggestion is a good one, and I will pull the head unit again to make sure that I haven't pinched or abraded a wire when I pulled the stereo a few months ago for a different problem.

It's drawing between 3.4 and 3.7 amps even with all of the interior and trunk lights off, which is a lot of draw, and if it were a short, enough to generate some serious heat. I'm beginning to think that there may be a short near the alternator, somewhere that can drain that kind of power without starting a fire.