lemurss

So I bought this car as a seizure, and so it has some mysteries that I have to figure out on my own. It had a custom audio system in the trunk, but no head unit, and the computer and alarm immobilizer units were connected, but laying on the floor.

I bought a nice head unit and installed it to the aftermarket wiring harness that was there, and it powered right up, along with the system in the trunk. However, once all that was connected it drained the battery at night to the point of needing a jump start.

I disconnected the system in the trunk, and it still drains it. I had a mechanic friend of mine take a look at things with a test light that can show if we have a draw when the car is off. It's just a basic light, and doesn't measure actual current numbers.

When he disconnected the positive terminal on the battery and hooked up the test light between the positive cable and the positive terminal the alarm immobilizer started making a pulsing noise and the pulsing reflected on the test light. It could have just been that it didn't have enough power to do.. whatever it does.. but when we plugged the head unit back in (with the test light between the battery terminal and cable) the pulsing stopped but there was still a draw.

We checked the wiring on the head unit to make sure that the constant power line was hooked up correctly. We are a bit stumped because this immobilizer is preventing us from being able to test things. The clues (no headunit when I bought the car) point to the previous owner having the same problem and resorting to removing the headunit until the problem is found.

We are stumped..

Any ideas? I'm desperate.

Charlie

You need a volt meter that will measure current draw.

Measure the draw with the radio (radio off and ignition off) plug connected.
Measure the draw with the radio not connected.

lemurss

Thanks I will try to find a meter that shows that

touareg

I would look to make sure the radio alarm to ground wire is not being triggered. Pretty common for people to ground this loose black wire thinking it is part of the radio install (it is but only if you want the alarm to trip if the radio is slid out) Normally it is connected to a reed switch on the radio sleeve, and grounds to the radio when it is slid out (being stolen)

If this is grounded 100% I would think maybe the alarm is being tripped, but since you hear no sound, I question if the horn works?

I think it uses the horn for the alarm.

lemurss

duplicate

lemurss

I had to pull the horn fuse because the steering wheel button was shorting out.

Any suggestions on how to identify this black wire? What is a reed switch?

lemurss

I guess it's not the headunit... I disconnected the head unit and drove the car around a lot last night and got the battery charged up enough to start the car without a jump, and then this morning its dead again.

The immobilizer is clicking like 5 times a second. If I move the dome light switch forward the clicking speeds up, if I move the switch towards me and the dim light comes on the clicking stops.

Charlie

The reed switch grounds a black or could be a brown/blue wire when the radio if removed to I assume set off an alarm. Not sure if all 968's had this.
Look where the radio goes and see if you can see this wire and if it is grounded.

Are you sure the horn switch is grounded or could the alarm be sounding the horn?

lemurss

Ok so a lot of stuff took place today. I jump started the car and drove to Harbor Freight to get a multimeter. After 20 mins of driving it started right up at the Harbor Freight and got me home.

I disconnected the negative terminal on the battery (and also used the positive later just to be sure) and connected the multimeter in between to measure DC mA. At first it appeared that I had 750mA of draw. I pulled every fuse and noticed a major drop when I pulled out the engine and trunk accessory light fuse. I found that the light in the trunk might have had some wires crossing. All seemed well after that, but only when the hatch was open. When the hatch was closed there was still a draw of 100mA. I thought it might have been the electronic key latch because when I disconnected it the draw appeared to go away, but it might have been my imagination.

SO... I pulled every single amp and fuse at once and there was still a 100mA draw. The only thing that I could find that would reduce that draw was to pull off the BLACK connector on the alarm immobilizer. Of course then the car wouldn't start, only crank.

Thoughts?

Charlie

I just checked mine and it has a 20 milliamp draw. I would put all the fuses in and measure the draw with the alarm hooked and unhooked.

Does the horn sound with the alarm unhooked. Just trying to figure out if the horn is shorted or if the alarm is making it sound????

lemurss

How do you hook and unhook the alarm?

I drove it around quite a bit and never heard the alarm horn, and the horn was working, but due to a short in the horn button itself, i had to pull the horn fuse to avoid embarrassment.

So in addition to all my problems tracking the drain today, as soon as I put everything back in the antilock brake light is on, the speedometer doesn't work, and the idle is a little more rough. I don't even know how that can be possible, but the alarm immobilizer module sounds like it has a bad connection at the harness because if i wiggle the harness i can hear the module making lots of clicking sounds.

Charlie

What I was suggesting was to unplug the black connector on the immobilizer. With all the fuses in if you pull the black connector how much does it drop the current draw?

lemurss

When I pull the black connector it drops to zero..

Charlie

I would think your clock and radio memory would show some draw?

lemurss

Well, there is one little problem, lol, at this point in the diagnosis i must have blown the fuse inside the multimeter because the more sensitive modes wouldn't work, so I was forced to use the 10A mode. I would see a .1 if I had a 100mA draw, but I don't think it had the ability to show something as minute as a 5mA draw. I'll have to go guy another or figure out how to repair this one..