On The Road

Getting a clearer view of window regulators

We’ve all been in a situation where we’re driving along and try to use some feature of our car and it doesn’t respond.

That includes the window controls. It always seems like the windows won’t roll up or down when you need them most – at a drive-thru or car wash, on a really hot or cold day or when it starts to rain.

At our shop, we repair or replace at least two or three window regulators each week.

There are two types of window regulators – the cable-driven regulator and the scissor-driven regulator.

Most Japanese cars come with the scissor style, and most European cars use the cable-driven design. Over the years, I have found the scissor design more reliable than the cable-driven design.

Parts of the regulator

To better understand the problem, I must first explain how the window regulator works. The window regulator is basically an elevator for the window. Most window regulators have five main parts:

• The main track that holds the window rail; the window is bolted to the rail.

• The frame that the main track is connected to; the frame is bolted to the inside of the doorframe.

• The pulleys and gears, which are bolted to the frame.

• The cable, which connects to the top of the window rail and is routed through a pulley, a gear, another pulley and then to the bottom of the window rail.

• The window motor, which is bolted to the gear assembly.

Once all of the parts are in place, one can command the window to go up or down.

Scissors vs. cable

The scissor design is more basic and has fewer parts. It has two arms – the gear arm and the main arm – that fit together like scissors. The main arm bolts to the doorframe and has a mount for the electric motor. The free-floating gear arm has a built-in gear on one side and the other side is a mount for the glass. The gear arm pivots on the main arm. By commanding the motor to go forward or backward, the window will go up or down.

Cable-driven regulators give customers the most trouble. The weak points of the design are the plastics pulleys. Electric motors have a lot of torque. If the window glass gets stuck, the motor will tear the pulleys apart. The cable then jumps off and the window falls down. In rare cases, if the window glass gets stuck on a scissor design, the motor will bend the gear arm or break the gears.

Obviously, the key is not to let the glass get stuck.

Preventing the problem

Following are a few tips that can help avoid the problem.

• Don’t hold the window switch long after the window has gone up or down.

• If it has been a long time since you have operated a window, or if the car spends a lot of time in the warm sun, make sure that the window seal isn’t stuck to the glass. If you try to operate the window when the seal is stuck to the glass, it will tear the pulley off. Use a plastic knife and run it between the seal and the glass – this always frees the glass.

• Try to operate the window regulator at least once a week so that your windows don’t get stuck in the first place.

Matt Pataky owns Sunnyvale Foreign Car Service, 15 Pioneer Way, Mountain View. For more information, call 960-6988, email This email address is being protected from spambots. You need JavaScript enabled to view it. or visit sunnyvaleforeigncar.com.

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