Since fall is in full swing, I thought writing about gremlins would be fun.

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What Is A Gremlin?

A gremlin is a mischievous creature in English folklore that sabotages machinery. This myth became very popular amongst aviators during WWII and quickly spread to the automotive industry.

Illustration by Sam Berman (1943).

A Quick History Of The Gremlin

In 1970, American Motors (AMC) interestingly chose “Gremlin” as the model name for their new economy car despite the negative connotation. The vehicle’s designer reportedly tried to rebrand the word as “a pal to its friends and an ogre to its enemies.”

Car advertisement

Today, the word gremlin is usually only brought up when a vehicle exhibits odd or unexplainable behavior.

I recently encountered such a situation on one of our backup vehicles; a 2003 Jeep Liberty. One evening, I was walking past it when I noticed the left rear window was about halfway down. It caught me off guard because I knew I had put the windows up before I parked it a few months ago.

Black Car
Finding the window halfway down...

Various questions flooded my mind. Did someone else drive it recently and forget to put it up, or did it go down on its own somehow? How long has the window been down without anyone noticing? Is there any damage to the interior from rainwater?

I grabbed the key inside the house and started to investigate my concern. Thankfully the interior wasn’t wet, but the back seat did look dirtier than usual.

With the ignition in the ON position, the master window switch would not operate the window up or down. The window motor inside the door could be heard operating, but the glass wasn’t moving. I took hold of the window glass and was able to move it up and down in the window channel, which confirmed it was a mechanical problem rather than an electrical issue.

Manually moving the window glass down.
Manually moving the window glass up. 

I’ve seen several different internal door problems that can produce these symptoms; the window glass mounting tabs can separate, or the window regulator linkage can break.

Window Mounting Tabs

Window mounting tabs secure the window glass to the window regulator. Tab designs vary from vehicle to vehicle, but they are mostly made of plastic and permanently glued to the glass. If the plastic tabs break, window glass replacement is often necessary.

Side window glass with window tabs. 
Window glass tabs.

Window tab replacement isn’t impossible, but it’s usually not practical from a business standpoint. Tabs are not typically serviceable, meaning they are not sold separately as direct-fit replacement parts. They can be purchased in a universal format, but there are no guarantees that the fitment will be correct for the regulator mounting hole or glass channel. Then, if a suitable replacement part is sourced, there’s the problem of removing the broken plastic and epoxy from the surface of the glass without breaking it.

The Window Regulator

A window regulator is a mechanism powered by the window motor that raises and lowers the window glass. There are multiple regulator designs; some use lever arms, while others use cables. The regulator must be replaced if a cable snaps or the linkage pivot point separates.

How A Window Regulator Works

To help illustrate how a window regulator works, imagine you are using a pair of scissors. As your fingers move away from each other, the height of the scissors lowers, and when they come together, the height raises. This is precisely how a scissor-type window regulator raises and lowers window glass.

Scissor-type window regulator. 

A cable-type window regulator is comparable to an elevator, where an electric motor pushes and pulls on a set of cables to raise and lower the load. This style is popular in modern vehicles.

Most new window regulators now come with pre-installed motors; this was not the case when I started my career. The benefits of replacing a window motor/regulator assembly are that the issue will be resolved whether the failure is in the regulator or the motor, there is less replacement labor involved, and it alleviates worry about the OK portion of the assembly potentially failing in the near future.

Removing The Door Panel

Now, let’s get back to the Jeep Liberty. Using a special tool to suspend the window glass, I removed the door panel mounting screws and popped the door panel retaining clips loose.

Suspending the window glass with a special glass holding tool.
Removing one of the door panel mounting screws. 

Next, I disconnected the linkage to the door handle and removed the panel. Then, I removed the audio speaker and gently pulled the vapor barrier away from the door to expose the internal door latch and window mechanisms.

Disconnecting the door handle linkage. 
Removing the door vapor barrier. 

When I removed the spring clip that connects the window tab to the regulator, I observed that the tab was intact, which isolated the issue to the regulator. Next, I loosened the mounting bolts for the window motor and regulator, unclipped the door lock linkage, and positioned it out of the way.

Loosening the window motor mounting bolts. 
Disconnecting the door lock linkage. 

With the window motor and regulator loose, I was able to access the window motor’s electrical connector and disconnect it. I then removed the window motor/regulator assembly from the door.

Removing the original window motor/regulator assembly from the door. 
Inspecting the original window motor/regulator assembly. 

The new window motor/regulator assembly was visually different, presumably an updated or improved design over the original. I transferred the bolts from the old mounting brackets to the new assembly and installed it into position.

Inspecting the new window motor/regulatory assembly. 
Installing the new window motor/regulator assembly.

After reinstalling all of the other parts in reverse order, I validated the repair by operating the window using the master window switch; it worked perfectly.

Verifying that the window closes properly.

In The End

In the end, there wasn’t any window gremlins for me to battle; sorry for the disappointment!

I do have to admit, though, this particular failure initially felt like someone had meddled with the vehicle. Perhaps through this experience, I got a taste of how those early aviators felt when something went wrong. But, of course, I can’t begin to imagine how spooky it would have been at 20,000 feet!

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