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Porsche 928: Why is My Window Stuck?

Eliminate the disaster of a stuck window. Learn to isolate faulty components here.

By James Karuga - April 17, 2015

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

When either of your car windows begins to stick, it limits where you park your car for safety reasons, and before engaging in any drive, you have to consider the weather. If its rainy, snowy, windy, or dusty and one or more of your windows can't close, then driving in those conditions will be very unpleasant. A stuck non-closed window, exposes components like the car lock and window mechanism to road salt, debris, and rain and can cause them to malfunction.

If your Porsche 928 has stuck windows, there are components to examine that could be the problem source. After discovering the root of the issue, you can decide whether to do the repairs yourself or seek professional help if it's challenging. The advantage of doing it yourself is that you save money and learn in the process. Read on to troubleshoot a stuck window in your 928.

Step 1 – Check the window regulator

The lower part of a car's door panel houses the window regulator. The regulator has metal strips and gears on the half circle component. The gears are turned by motor gears to generate movement that pushes the window up or down. You can detect a window regulator problem if the motor moves but the regulator doesn't.

When the window regulator has gone bad, you can usually tell by a slow, noisy-moving window. You can usually extend the regulator's life by lubricating the actuator often.

Figure 1. Window regulator and drive gear.

Step 2 – Check for clogging or wear in the power window motor

If you notice the 928's windows begin to slow and then stick when moving up or down, chances are the power window motor is old and worn out or clogged by dirt. A problematic motor can also be noticed if one window is okay but another is stuck. The power window motor's gears rotate the window regulator gears which then move the window.

If you feel the motor is not old enough to wear out, check if it has trapped dirt. Dirt can appear as old hardened grease inside the motor, clogging the gears, stopping their rotation, and causing the window to stick. Car experts advise for application of liquid grease to lubricate as it won't harden with time. If you want to test a motor, plug the power wires connected to it to a voltmeter; if the reading is 12 volts and the motor wasn't rotating, the motor is faulty. A refurbished power window motor for the 928 costs over $160 online.

Figure 2. Power window motor.

Step 3 – Check the window relay condition

All windows for the 928 rely on one relay; if it blows due to current overload, the power windows will get stuck. One way to diagnose window relay failure is to check if the wires that bring power to it are loaded. You can test the power wires by using a voltmeter. If there is no power being transmitted, the relay has a problem.

Alternatively swapping a bad relay for a working one helps you know if the fault exists. Besides blowing up, window relays get clogged by dirt which insulates them and hampers power transmission through them to the windows. If the relay is damaged, a new one for the 928 is less than $30.

Figure 3. Window relay.

Step 4 – Check the door window switch condition

To test if power is being delivered to the 928's door window switch, plug the power delivery wires to the voltmeter. If the voltmeter reading shows 12 volts, then power is getting to the door window switch. If you notice one window sticks and the other is working, then test the switch of the sticking window; it may be bad. Also, failure to hear any motor sound could indicate a bad switch. Door window switches can be damaged by spilled fluids which corrode them. At times, slight clean up of the switch gets them working again, but if that doesn't work, purchasing a new door window switch for less than $20 works.

Figure 4. Check the door window switch.

Pro Tip

Wire connections to the door window switches get damaged at the door hinges, so always check to see if the failure originates there.

Step 5 – Check for a blown power window fuse

If all the windows stick and none of them move, check if the power window fuse is working. For that, use a test light, and on the fuse box, insert the test light on both the power windows' fuse endings. If the test light translucent handle bulb does not light up on one end, the fuse needs to be replaced. A new fuse for the 928 costs less than $10.

Figure 5. Power fuse locations.

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