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Complexities of Replacing Components on Your Car

Tech Notes from Tony Callas & Tom Prine

A customer recently came in slightly perplexed at some work he performed on his own 2006 997 Carrera S. The initial problem was that the passenger side electric window began to slow and strain when closing the window. Finally the motor stopped working completely. The customer purchased a new factory window motor, installed it and, to his surprise, discovered that the motor would not operate at all. By the time he came to see us he was more than a little frustrated. His demeanor changed when he found out that there was nothing wrong with the new motor, or even the way it was installed — it just had to be coded to the car.

In today’s world of increasingly complex automotive electronic systems, one of the realities is that components on the car must be recognized by its intended control system in order to communicate and function normally. This is simply known as a “handshake” between controllers. Another interesting fact is that various electrical consumers (a consumer is an electrical device) will share one module (as in the case of the window motor). The window motor and other items share a single module: the Door Control Module. The customer did not know this and did not possess the means to code the new motor and controller into the system. Today, professional Porsche repair facilities must have the electronic diagnostic equipment with the correct software designed to talk to the onboard systems of the car. These electronic diagnostic tools make it possible to program new components into their operational role in the car.

Unfortunately, the cost and complexity of owning and using these diagnostic scan tools make it unrealistic for most vehicle owners to purchase and operate them. Once the new component is installed and wired, the coding can take place. With the electronic scan tool connected to the car, there are about eight choices to perform during the coding procedure for the window motor. Once the coding is complete, the motor will be ready to operate but, in the case of the windows, they will also have to be initialized. This is the process of setting the operational limits of the window motors. The window initialization is done by moving the window all the way to its upper and lower stops via the window switch. Once the window reaches the upper stop, continue to hold the window switch in the up position request for approximately an additional 3 seconds, then push the window switch to lower the window. When the window reaches the lower stop, continue to hold the window switch in the lowerrequest position (again for about 3 seconds). Repeat as needed until the one touch activation works. The passenger window will not have one touch until the window reaches approximately 65% of the up position for the 997s.

The sunroof assembly requires a completely different process for initialization following the completion of all repairs. You push the sunroof switch to the vent or up position and hold the switch in this position until the entire initialization is completed. The sunroof should open to the vent position and stop. Nothing may happen for some time but, as you continue to hold the switch in the vent position, the initialization phase should start and the sunroof will begin to operate. Continue holding the switch in the this position.

The sunroof will fully open and fully close, thus completing the sunroof initialization process. You can then release the sunroof switch. The sunroof initialization might take a few attempts to get the process completed.

Another point to consider is the car’s system voltage when diagnosing, testing or performing an initialization. When an engine is running, the alternator is tasked with producing voltage to charge the battery and power all the electrical consumers in the car. Normally the alternator will produce in the neighborhood of 13.5-14.5 volts and the electrical consumers and circuits are designed to operate in this voltage window to perform properly. However, this voltage is not available when the engine is not running and the key is turned on for diagnostic and testing purposes. During this testing there is a heavy load against the battery due to all the electrical consumers operating. It is highly recommended to have a Power Supply connected to the car to achieve the correct voltage and avoid draining the battery.

A Power Supply (not a battery charger) will provide a constant and stable voltage feed at high amperage output and without stray A/C voltage being emitted. With the Power Supply connected the electrical system of the car, you will see the same conditions as if the engine/alternator were operating.
Enjoy your Porsche

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