Brandon Buchanan

New to Porsche, so forgive any obvious or dumb questions.

I have a 2003 986 that I am working on for a friend. I am experiencing an electrical problem and I need some advice on where to start.

Intermittently, when you open the driver door, the entire dash including radio and climate controls are completely dead. The car will still start, and other items such as the top, headlights, ect are fine. The dash is completely dark. When this happens I can disconnect / reconnect the battery and everything returns to working normally. Obviously pulling the battery is resetting something, but I need to know where to start looking.

Any Advice?

Macster

Reads like a connection problem. Whenever someone reports a car's electrical system acting up I always think "ignition switch". (So too do a lot of other people.) I also think "mice" but other people not so much. And there is always the concern water has gotten into the cabin on the cabin floor or is in the doors.

If the previous owner was one to hang a ton of keys off the key chain that held the Porsche key the switch becomes more likely. But the absence of a heavy key chain doesn't eliminate the ignition switch.

The time I watched a tech "test" an ignition switch he tried wiggling the key as it turn the key on and off again to see if by wiggling he could affect the dash lights or any other electrical circuit into manifesting the wrong behavior, coming on when it was not supposed to or not coming on when it was supposed to.

Check the cabin floor for signs of moisture. Trouble is water could have been in the cabin then dried but the damage was done. The car's security module is located under the driver's seat -- but confirm before you remove the seat -- and you probably should check this for signs of water damage.

Check the body water drains. There are a couple in the front trunk located on either side of the battery. You'll have to remove the Torx screws that secure the plastic panels -- you'll need a Torx tool bit set with the security defeated feature -- a smalll hole in the center of the torx bit hole -- and expose the drain basins and drain hole/tube. If full of trash... While you are there carefully remove the trash and be sure water flows down and out the basin and to the ground.

There are two drain basins located on either side of the top under the clam shell arms. You'll have to put the top in the "service position" to expose these rear drains.

Another area from which water can enter the cabin: Feel along the door bottoms -- the carpets -- for any signs of dampness. What can happen is the door mebrane fails -- due to age (both have failed in my 2002 Boxster) -- and let water from the wet side to the dry side. Initially this results in odd window/door lock behavior but if left unaddressed electrical gremlins can begin to appear in other seemingly unrelated areas. I note the odd behavior you report appears when opening the door and it is the door lock controller that detects the door is open and signals the rest of the car of this.

If the car has sat a while unused mice become a possible explanation. While you are working on the car keep an eye peeled for signs of rodents. Trash/litter on top of the plastic underbody panels is a sign, but -- but really anywhere in the cabin, trunks, in/on the engine. Bare patches of carpet another. The critters like to remove the fuzz and use it for nesting material.) Gnawing marks on wiring, plastic hoses -- the ones that run under the car from the front to the back are favored.

Brandon Buchanan

So i had already planned on replacing the ignition switch. I got the old one removed, but was having hell getting the new one in. Long story short I discovered the original switch was a European version. Just different enough that the switch I have won't go in. I have ordered the correct one, and will try again when it comes in.

Brandon Buchanan

I replaced the ignition switch to no avail. I am starting to think it could be the central locking control, but at this point I am just guessing.

Macster

Absent being exposed to water the security module appears to be rather robust and long lived, but of course YMMV. The hardware/electronics in the doors is less robust, but nonetheless expensive to replace unless one has a high degree of confidence the in door hardware/electronics is in fact at fault.

A tech with access to a Porsche diagnostics computer could possibly identify the source of the problem. He can query the security module for any errors and if any these could shed some light on the possible cause of the behavior.

(When my 2002 Boxster's passenger window was acting up: not dropping when the door was opened or worse dropping then going back up after the door was opened, when the car's security system would sound a mini-beep like a door ajar upon locking, or when the car door locks would activate on their on after pulling away from a stop; the tech checked with the car's security module and the error codes pointed to the door lock controller. He got the door card off and checked some other possible explanations -- hardware and electrical connections -- and finding none wrong replaced the door lock controller. Symptoms gone.)

There's not much you can do without a Porsche diagnostics computer but you can do a little bit of investigation.

The tech gave me a rundown on how the various items behave if they work right but a problem could exist even if all the items appear to behave.

Briefly, when either door handle is pulled the window should drop. This is a sign the door handle switch (and at least part of the door lock controller) is working. If you release the handle without opening the door the window should go back up. This is more confirmation the door handle switch is working ok. It also is a sign the door latch switch is working.

If the door handle is pulled hard enough to open the door the window should stay down. This is a sign the door handle switch and door lock controller and door latch switch are working.

Then when the door is closed the window should go up again. More sign the door handle switch and the door lock controller and the door latch switch are apparently working.

A weak or feeble window drop is a sign the window regulator is going bad, is bad. These wear out.

The above "tests" are not exhaustive though. The door controller is an electro-mechanical device, has some electronics in it, thus it can appear to work ok most of the time but not ok some of the time. But working ok most of the time is usually a sign it is bad.

Since you have apparently eliminated the ignition switch if the dash lights go dark when the door is opened this suggests the problem is in the door lock controller.

Brandon Buchanan

Hey Macster I appreciate the help.

Let me be a little more detailed in explaining the problem. Lets me start from the beginning.

1. After a fresh disconnect / reconnect of the battery cable, the car behaves perfectly. The dash, gauges, environmental all work fine. When the car sits a period of time (sometimes overnight, sometimes several days later) when I open the door, the dash, gauges, environmental are dark. I can start and drive the car, but nothing on the dash works.

2. When this dash dark event occurs, everything else seems ok. The windows on the doors behave as they should when opening and closing... The Top will go up and down... The interior lights come on and off.

When this happens, I can pull the battery cable and put it back on, and the entire process starts over.

Here is what I have done so far.

1. New Battery. The car sat for two years, so the existing one was shot
2. New Ignition switch... Just because it was easy and cheap.
I also had to drain the fuel tank, and replace the fuel pump and sending unit, but I do not think that is related.

So any further idea's would be appreciated. This car only has 33K on it, so its a shame that I can't get it to be reliable.

Macster

Just so it is clear, absent a Porsche diagnostic computer it is all supposition and guessing.

The battery disconnect/reconnect is just a power reset. That a power reset makes the symptoms go away suggests an electronics problem.

Then that the dash lights go dark when you open the door suggests the car's instrument cluster/dash controller is getting a message that the door is closed when in fact it is open. Note these cars do not have the old fashioned button that is worked by the door jam when the door is opened or closed. This functionality is all in the door smarts. The smartest item in the door is the door lock controller.

If you don't like the door lock controller for this -- and I can understand your reluctance, your desire for a higher confidence diagnosis -- I can't recall if I covered this but water in the door(s) can cause electrical gremlins that first appear with the door/window but later can appear at other seemingly unrelated areas. Even if the water has dried up if there are any signs of water on the dry side of the door, if the membrane is loose, has tears/splits, almost certainly water has gotten where it shouldn't.

Last but not least when I read the car sat for 2 years you know what that brings to mind? I may have covered this above -- I have not taken the time to refresh my memory -- but it brings to mind mice. Two years is a long time for a car to sit. Cars are very attractive to mice for various reasons. One doesn't have to live on top of a garbage dump or a trash pile have mice make an appearance. Mice are everywhere humans are. Mice like the same things humans like. Cars offer a secure shelter.

Mice like to gnaw, have to gnaw to wear down their incisors or these can grow to the point they will eventually kill the animal. Plastic, rubber are favored at least in cars. I've seen A/C vent tubing chewed through. The heavy rubber sheeting used to form radiator ducts. Plastic tubing under the car that carries fuel vapor. The mice will chew into this but stop when they get a snoot full of fuel vapor.

And wiring harnesses. I've seen a 996 Turbo Cab with a severely damaged engine wiring harness. But the mice can get at the wiring in the dash/instrument cluster too. The creatures may not have set up long term residence in the car. They might have visited it a couple of times and done some exploratory gnawing then gone away. Natural predators, and cats, dogs, traps, and even poison do take a toll on mice and if one of a pair got taken out the other one might have moved on. While the car is still an attractive place a (new) mate is even more a draw.

You have to really check over the car very carefully. While often the signs are unmistakable if the infestation was long term, a short term/brief infestation the only real signs after 2 years (with mice only being in/at the car a short interval) might just be gnaw marks on various items. But these likely won't be that visible. Mice do not like to be in the open and any damage they have inflicted will likely not be out in the open.

Techs use a hand and run all wiring and hoses/tubing feeling for gnaw sign. In really tight places a mirror on a stick and a good light are used.