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Porsche 928: Why is My Power Window Not Working?

Here are some potential causes as to why your power windows aren't working.

By James Karuga - April 8, 2015

This article applies to the Porsche 928 (1979-1995).

In normal weather, it's easy to ignore malfunctions of the Porsche 928 power windows. But just wait until you drive into a sandstorm or in rain; then it becomes a matter of absolute necessity to have the Porsche 928 power windows working as they should. The power window system is complex, and when it's faulty, its not easy to isolate the problem source. This article is a diagnostic walk-through that will help you isolate the cause(s) of power window system malfunction in your Porsche 928.

Step 1 – Is the power window relay faulty?

If you fail to roll up the windows of the Porsche 928 before turning off the engine, the power window relay retains a little amount of charge that rolls the windows up. If you notice that the power windows are not rolling up after switching off the engine, then the relay is faulty. A fault in the relay can be as simple as a broken wire or its connection plates being clogged with dirt. A broken wire can be soldered back, but if the relay has aged, a replacement is vital. An ordinary power window relay for the Porsche 928 costs less than $30.

Figure 1. Power window relay.

Step 2 – What's the condition of the power window motor?

The power window motor propels the regulator which moves the windows up and down. The regulator is the harness anchoring the car windows, and its gears are rotated by the motor. If the motor is old and damaged, the whole power window system of the Porsche 928 gets crippled. If one of the windows is static when others move, it could be a motor problem.

If you also test the window relay with a voltmeter and it has power, you can narrow the problem to a faulty motor. Also, if the Porsche 928 window switch indicates low voltage, then that may also indicate a motor problem. Buying a new genuine power window motor for the Porsche 928 costs from $200 and upwards on eBay.

Figure 2. Power window motor.

Pro Tip

The motor can be okay, but if the fuse connecting the power window system to the car's electrical system is blown, then the motor won't function.

Step 3 – How is the window regulator condition?

The window regulator is a pulley-like component located on all the doors that holds the mirrors in place. When the motor is running after the power window switches are on, it rotates the window regulator gears to move the windows up or down. The window regulator generates lots of friction, which causes its gears and hinges to wear out. That often results in the windows being stuck in the door frame. In other instances, the window plunges into the door frame and is trapped there. Auto experts advise to replace the power window regulator when that happens. The cost for a new Porsche 928 window regulator costs around $80.

Figure 3. Window regulator location.

Step 4 – How is the main switch condition?

The main power window switch controls all functions of the other windows. It's located on the driver's side, and its connecting wires are prone to damage from spilled beverages or rain when the driver's side window is open. When damage results, a new power window main switch is necessary, which costs less than $20 for the Porsche 928.

Figure 4. Power window main switch.

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