Saturn sunroof motor...limit switches?

Question

The sunroof in my girlfriends 2001 Saturn SC2 broke back in Aug and I was the unlucky recipient of receiving the task of fixing it. I did a little research and discovered that thousands of people have had the same problem. I purchased the replacement guides from sunroof doctor, installed them this weekend and have the module installed back in the car.

My question is this:

Before connecting the motor back up to the unit, the thought occurred to me that there is no evident limit switches on the sun roof assembly. My first instinct was that there must be limit switches in the motor that determine the start and stopping points. To test this, I connected all the wiring back the way it was and tested the motor (still not installed). To my surprise the motor spins endlessly when "open" and "close" are depressed. When "vent" is depressed, the motor will sometimes spin 2 revolutions and stop while other times it will spin about 5 revs then stop. I find it hard to believe that this is this complicated seeing as how many people have claimed to have installed the replacement guides and their sunroof is working flawlessly. I am weary of installing the motor back in the sunroof for fear of breaking something from the motor continuing to rotate. Any advice you can give me would be most appreciated. Thanks

-Jesse

C. E. White · Accepted Answer

Current limiting. Just like power windows. Ed

Steve W. · Answer

They are current limited. Basically when the window hits the end of the track and stops the motors current usage spikes. When that happens the module senses it and stops the motor. This is the same method that the power windows use in most vehicles.

Scott Dorsey · Answer

The logic that drives the motor is sensing the motor current, and decides it has come to the end of travel when it exceeds a certain amount. You can simulate this by putting on a heavy leather glove and applying resistance to the motor.

Note that if the logic driving the motor goes bad, it WILL break things. I have seen this a couple times.

--scott

HLS · Answer

lower the window totally, to facilitate toll booths, ATM machines, and the like.  To  raise the window, you had to hold  the switch constantly, naturally, to diminish the  likelihood that a child would get its head caught in the closing window. Our new car WILL raise the window with a single flick of the button, so that  tells me the process or technology has changed a bit.  Is it still current sensing -  just more sensitive - or is something else different.

Scott Dorsey · Answer

Damned if I know, but I'd guess it was probably still current sensing.  If you are curious, you can pull the panel and look for limit switches.  I bet you don't find any, though. --scott

HLS · Answer

Me either.... You can imagine the lawsuits if this system resulted in the decapitation or injury of a child or a dog (we men are just acceptable casualties ;>)

I am relatively sure it is a near litigiously failsafe system, but dont know how it works

Steve W. · Answer

Still current sensing on most GM some of the high dollar imports use a  switch mounted to the window track.

Tegger · Answer

"Steve W."  wrote in news:1226454888    snipped-for-privacy@isp.n: Wouldn't current-sensing be more reliable, not having a mechanical  component the way a microswitch would?

Steve W. · Answer

It depends. If you use a quality switch it would likely outlast the vehicle. The way they are set up is that the glass mounts on a pair of rubber mounts. Pressure on the top edge of the glass stops it in the event of a blockage. It also is faster reacting as well.

Jstein · Answer

News==---- #1 Newsgroup Service in the World!  >100,000 Newsgroups > ---= - Total Privacy via Encryption =--- So I was sure after everyone's posts that this motor was in fact current limiting.  To test this theory I hooked up all of the wiring the way it should be and had a helper press the switch to both open and close positions while I grabbed the gear with a pair of water pump pliers to simulate a load.  Much to my surprise the motor wanted to continue to spin. I am a bit confused as to how this is possible. Applying a load on the motor in the manner in which i did should apply enough resistance to the motor to kill it.  What am I missing?

Steve Austin · Answer

I've installed some of those cheap Chinese window motors that one touch  up and hold the button for down.  At least until I cut and swap the wires.

Saturn sunroof motor...limit switches?

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