Power Windows: Getting a Lock on the Problem

New homes do not have power windows, but new cars do. How odd. At the push of a button, the car window goes up or down, at least until the mechanism buried inside the door breaks. Then the convenience of power is transformed into the mundane problem of a window stuck open or closed.

Power windows, now standard equipment on the majority of new cars, often last the life of a vehicle without needing repairs. But when a car does encounter window problems, the owner will face an unpleasant repair bill.

Gas-fueled vehicles could not go very far without electric motors that operate many systems, including the power windows.

With so many devices operated by electric motors, problems with them are not uncommon.

Under the hood, electric motors operate most fuel pumps and engine fans. Antennas, seats, door locks, windshield wipers and minivan doors are all powered by electric systems. In coming years, electric motors will operate water pumps, engine valves and even air conditioning compressors.

A reader not long ago wrote to complain about his Ford’s power windows--which opened and closed with a jerky motion, sometimes requiring a little push or pull from the driver to behave properly.

The problem was solved temporarily with a spray lubricant, but the jerky movement returned. Another type of lubricant also provided temporary relief. “Am I missing something?” the owner asked.

Well, of course. The lubricant failed to fix the problem. And who wants to spend every weekend lubricating the inside of a car door?

The power window is certainly not one of the most sophisticated pieces of equipment on a car, but like a cup holder it is expected to perform flawlessly for the owner’s comfort. And as with a cup holder, a lot of car makers are fussy about the design of their power windows.

Most people never get to see the workings of a power window. They all have a little bit of Rube Goldberg design in them, using various combinations of gears, levers, pulleys, cables, felt tracks for guiding the glass and rubber seals.

Not only do the windows have power action, they also must withstand winds of 80 mph or more, driving rain, ice and baking desert heat, not to mention the abuse inflicted by 4-year-olds who are infinitely fascinated by putting windows in motion.

Almost all power windows have two key parts, the electric motor and the regulator--the mechanical linkage that transforms the rotating motion of the motor to the up and down motion of the window.

The most common regulator is a scissor-type arrangement that has four bars arranged in a parallelogram. Ford typically uses a scissor regulator married to a plastic gear system on the electric motor. Some vehicles, including some Volkswagens, use what’s called a goldie cable or a bowden cable. Both use cables and pulleys to provide lifting motion to the window.

Regardless of the type of regulator used, problems with power windows typically occur in four areas: a weak or broken motor, a poorly aligned window, a worn-out felt track or a binding regulator.

If the window is slow to move, particularly when it is going down, the problem is usually a weak motor, said Sam Memmolo, a master mechanic and nationally recognized auto repair expert from Georgia.

The only way to be sure is to open up the door and inspect the system. Felt tracks often become bunched up, creating obstacles for the window. Attempts to straighten the felt usually fail, so it’s best to replace the tracks if there is any wear on them. Regulators should be lubricated at their pivot and movement points and checked for proper alignment.

If those items look like they are in working order, then the problem probably is with the motor. A mechanic can perform a voltage check to determine whether it is getting current and whether it is shorting out. A new motor can cost upward of $100 and that much or more to install.

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Ralph Vartabedian cannot answer mail personally but responds in this column to automotive questions of general interest. Write to Your Wheels, Business Section, Los Angeles Times, 202 W. 1st St., Los Angeles, CA 90012. E-mail: ralph.vartabedian@latimes.com.