With all the electronic gadgetry in our cars today from ABS to PDK, it is hard to believe that when I started driving in the early ’80s that power windows were such a big deal. That’s right, you could actually open the passenger side window from the driver’s seat with just the flick of a switch!

Back in the day, power windows were simply manual crank windows that had an electric motor attached to where the hand crank would normally be. There was a switch that reversed polarity to the motor and made the window go up or down.

These old systems were super simple and reliable, and rarely had a problem other than an occasional switch replacement. These systems were used all the way through the very late ’90s in all US Porsche street car models.

For coupes with window frames there was not much to go wrong. But if you had a targa or cabriolet, there were always issues with window height and the glass getting caught against the seal. When you don’t have a window frame, the glass must seal against a rubber seal with a lip. The glass must be tight enough against the seal to keep wind and water out but not so tight that the glass catches against the seal when you open/close the door.

It is not as easy as it sounds. In actuality, more times than not you had to have the glass adjusted very tight against the seal to keep the wind noise to a minimum. After closing the door many times, the glass would get caught on the outside of the seal. With this enormous air leak, you would lower the window, allowing the glass to pop back in under the seal, then you would put the window back up and the glass would be in just the right place.

When the Boxster and 996 emerged in the late ’90s, Porsche completely changed their power window game. There were no more window frames, and with convertibles and coupes sharing the same window design, some Porsche magic was in order.

At this point, power windows were no longer directly controlled by a switch. They were now controlled by a computer. This had to be done because windows had to perform many tasks, not just lowering or raising from a switch. They must automatically drop down when the convertible top is raised or lowered. They must also raise or lower automatically from a remote or outside door key tumbler. But most importantly, they must lower slightly when the door is opened and then pop back into position when the door is closed for perfect door-glass-to-seal mating.

Let’s look at how this magic trick is performed.

So, you are sitting in your Porsche and you want to get out and go into the house after a long day at the office. The first thing you do is pull on the interior door handle. The handle has a micro switch that tells the computer, “Hey! He is about to open the door—hurry up and lower the window just a smidge!”

So, the computer lowers the window about a half of an inch the instant you move the inside door release. When you fully pull on the inside door release, a cable attached to the door latch releases the door and enables you to open the door and get out of the car. But wait! As soon as the door latch is open, it sends a signal to the computer to tell the window to stay down. “Hey window, stay down for a moment while my owner gets out of the car.” The window complies, but only until the door is closed again, at which time the door latch signals the computer to tell the window to raise back up a half an inch to the normal position. We don’t want any of those nasty wind noise air leaks!


Control unit as is sits under driver’s seat

Getting back in the car from the outside is the same procedure, but this time it starts with the outside door handle instead of the inside door handle.

But what about when this orchestra of cooperation fails? You will usually notice the window failing to drop that half inch and the glass catching on the seal. Sometimes the window will go down that little bit and just stay there.

Let’s take a look at each circuit’s job and how to determine what portion of this system is at fault. Starting from the driver’s seat, pull gently on the interior door release. The window should make a noise for about 2 seconds, drop down, and then pop back up when released. If it makes no noise at all, you have a bad microswitch at the interior door handle. If it does make noise but doesn’t drop or barely drops, you have a bad window regulator. (More on that later).

Now, open the door and stand outside the car. The glass should be dropped slightly, and when you close the latch the window should pop back up to the normal position. You can close the latch while the door is open with the tip of a Phillips screw driver.


Sliding the tip of the screw driver into the latch simulates a closed “latched” door.

Now pull the outside door latch and listen to the latch click loudly and the window pop back down. If it doesn’t do any of this stuff, you have a bad microswitch in the door latch and it must be replaced.

Now you can close the door. From the outside, pull gently on the door handle and the window should drop slightly before the door opens. If it is not working properly you have a bad latch just like in the paragraph above.

Window regulators; new vs. old:

Window regulators are the most common failure for these newer window systems. Old systems used a huge gear-driven scissors of sorts to raise and lower windows, and they rarely failed.  However, they took lots of power, were slow and heavy and fairly expensive to replace. The newer systems are much lighter and operate the window with much less drag and at greater speed.

Unfortunately, the new regulators are made of a long cable (the size of a bicycle derailleur cable) and plastic wheels. The down side with these newer systems is that they wear out much more quickly. Not only are they not as durable as before, but they are in use twice every time you open the door. In an older system, it might be years before a passenger side window is even used, and the drivers’ side is only used when ordering a Frappuccino at the Starbucks drive-thru!

Even if you just drove your newer Porsche to work daily and made no extra stops or runs through the Starbucks drive-thru, you would be inadvertently operating the driver’s side window over 1000 times each year! That is how they get worn out so quickly.

Window regulator Testing and inspection:

The most common failure is cable stretching and fraying. Put the window all the way up and down. Does it sound like it is grinding or jumping? If so, it means the cable is badly stretched or fraying and about to break. Replace it as soon as possible so it doesn’t leave you stranded with a window that won’t go up, leaving you with a car that can’t be secured.

The stretch test:

Here is how we test the regulator cable that we can’t see because it is deep inside the door. With the door closed, attach a piece of masking tape to the trailing edge of the window between the glass and the rear seal. Cut the tape with a razor blade right at the glass/seal border. (Don’t cut the seal!)

A piece of tape cut in two, marks the resting position for the window.

Now pull the door handle and measure the amount the window glass dropped. A new window regulator will drop the glass about 13mm.

The distance between the two top edges is your checking distance; which ideally is 13mm. use a small ruler or caliper to get your distance.

As the regulator wears, the amount the window drops will decrease. The reason is because the motor moves the cable a set distance. As the cable stretches and gets slack, the motor has to pull the slack out before it can move the window. At 13mm of slack there is just nothing left to move the window.

Once the drop distance becomes 4mm or less it is about time to think about window regulator replacement. When the back of the window tilts back and the front doesn’t move, you are living on borrowed time. (The slack is mostly in the front edge of the glass).

Measure both left and right sides and you will notice a difference, as the driver’s door usually gets so much more use. Well, unless you are really popular and have friends that want to go places with you. In that case, a worn out passenger-side regulator is kind of like being voted the most popular kid in high school.

Okay, so maybe it’s just a window regulator and not a measurement of popularity….



Good luck.