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Boxster Bath-“Light control module failure”

When you work in an automotive repair facility and it starts raining, it’s only a matter of time before the tow trucks start rolling in. Usually the problems range from dead batteries to wet ignition system failures. One particular morning, we were graced with what could only be described as a much younger German version of Stephen King’s Christine. It was a 1997 Boxster, which had an extreme case of demonic possession.

The car would not start, the top and door locks would not operate, and the lights were flashing like a bad 70’s disco video. Being suspicious of water damage on this very wet day , we starting poking around and found a non-factory installed option for this Boxster; an indoor swimming pool.

Under the driver’s seat was about 2 inches of standing water. Normally this would be a small task for a good wet/dry vacuum. However on this model vehicle, a very important control unit was taking a bath in the depths of this new pool.

This little black box controls everything that is even remotely related to the alarm. This includes the top, the door locks, the windows, the lights, and of course the starting of the vehicle.

After removal and disassembly of the control unit, it was apparent that this was not a single incident damage issue. The printed circuit board showed extensive water damage that had occurred over a long period of time. Each time the car was washed a small amount of water would make its way to the pool area, and take a small bite out of this control unit. When the car was left in the torrential downpour, the control unit was drowned for the last time with no recovery.

A car should be able to withstand a little rain, shouldn’t it? Yes it should, and it would if all was well. But this Boxster had one tiny little problem, a tiny plastic problem. The problem was in the water drains for the convertible top. As water runs down the back of the top fabric, it drains into the top storage area. On the bottom of this area there are two drain holes, one on each side. But this car had a little plastic umbrella stuck in the left drain. (See figure #1)

Notice the top pin cover (umbrella) just above the drain hole.

This umbrella is intended to keep dirt and debris from entering the hard top locating pin socket. When a hardtop is used this pin is usually removed and discarded. With the left drain tube blocked, the water level increased until it had no place to go but behind the seat. This is why you should check the carpet behind your seat after washing your car or leaving it in the rain. If it is wet, be sure to check the drain holes and their operation.

When the drain holes become clogged, the excess water will saturate this back

carpet piece until a pool of water collects under the seat (and over the control unit).

Checking the drain tubes is easy; just activate the top until the metal cover is fully open with the top in the up position. Look in the top storage area to see if both drain covers are in place. Testing the drains is as easy as pouring some water over the drain holes, it should quickly drain onto the ground in front of the rear tires. If this is not the case, remove the drain covers and blow some compressed air through the drains. Anything caught in the drain should shoot out the bottom of the car.

Good Luck