Background:
98 coupe bought in Feb 08 with 112K on the odometer. Many months after getting car driver window wouldn't go down. Could hear the relay click AND the lights (shining against the garage wall) would noticeably dim for the second or so that the relay was latched in.

Based on some reading on the forum I pulled panel, removed speaker, briskly tapped the metal end cap of the motor with hammer. Window returned to normal operation. This fix lasted for a while then problem occurred again, seemingly at random times. After having to "fix" the window this way ~5-6 times over 3 years I decided to actually FIX it.

Given my symptoms, I decided it must be a bad window regulator. I based this diagnosis on the fact that when the relay contacts would close (but window not go down) that the system was passing enough current to noticeably dim the lights. I surmised that if the relay contacts were bad that they wouldn't be passing enough current to dim the lights. So I replaced the window regulator about 1 year ago.

Now:
I've had my new window regulator not work approximately 4 times now. Twice I fixed with the hammer to the motor method. Once it spontaneously fixed itself. The last was this morning when I tried to roll down my window to show my badge to the guard coming into work .

So... either the regulator didn't fix the problem or I got a bad regulator- how likely is this? I can replace the door module, or take the time to desolder and replace the relay on the module. But I would prefer to actually understand the problem rather than just throw parts (and time and $) at it while crossing my fingers.

For you electrical experts- do you think it's possible for the relay contacts to pass enough current to dim the lights but it not be sufficient to make the motor move- assuming the motor isn't faulty?

HELP!

 

I've read that supposedly the passenger and driver side control modules can be swapped.... so I decided as a troubleshooting step I'd pull both door panels, verify P/N's match, and swap them. If the problem switches to the passenger side window then the problem is in the module, if it stays with the driver side then the nearly new motor is the problem.... except as of this morning the driver side window is spontaneously working again. The gremlins are going to drive me nuts.

I may go ahead and pull the passenger side panel just so I can verify the module P/N is the same as the driver side for the NEXT time this thing messes up. Can anyone with experience with the window modules on 97-99 C5's verify that the modules are actually interchangeable?

Anyone got a working 16257811 module they want to sell for reasonable price? And not sure why, but this number doesn't even return a result when I search GMPartsHouse.com. Is it dealer only item or no longer available?

 

Thanks for the link to the post showing both modules. I'm fairly sure from the reading I've done that the module for the driver door changed in 2000. I'd assume the passenger door did as well.

I've already looked at the selection on ebay and may end up getting one from there.

As for the P/N not showing up for a new parts search- and I tried more places than just GMPartsHouse.com- it's been my experience that when a number has been superseded (which happens often as you pointed out) a search for the old number will return a result referencing the new P/N. However, that didn't happen for this module.