'92 300SE - Replaced both rear regulators. Non OEM parts. Comparing what I bought to what I had (which is OEM), can't tell the difference. Pullies, cables, springs, etc appear identical.

Before repair, both doors worked fine in the downward path. The passenger-side (p-side) door wouldn't roll up without assistance. The driver-side (d-side) would occasionally emit the dreaded pop-pop-pop when reaching the top, so I replaced both of 'em.

Now, d-side when rolled all the way down causes the cable to go slack. (I think same can be said for p-side - I've not checked) Didn't pay attention to how the OEM unit acted, but I think this is a normal condition - the springs are what keep the cable taught, and when you roll the window to either of it's extreme positions, the spring is compressed and the other side of the cable goes slack because there's no spring tension to take up the slack. When this occurs on both doors, you get the pop-pop-pop sound. In express mode (d-side only tested) the pop sound is brief in express mode. It is constant if you're 'manually' controlling the window with the button at the first detent position - until you release the button.

Express up and down is unreliable on both doors. If I program the driver's side door and press express down and allow the window to go all the way to the bottom, it won't express back up. If I stop it mid-travel, it will express back up. If I stop it past 2/3rds down, it will express back up sometimes, other times it catches at about 2/3rds and reverses briefly - like there's too much load on the motor.

I've lubed the sliders with some good silicone lubricant. I can't see where there's anywhere else to adjust the glass or places to lubricate the mechanism. On the driver's side window, you can see just a tad of the outer glass at the left side of the window when fully up - the right side is covered by the gasket. AllData says there's supposed to be a 3mm gap left, right and top between the outer glass and the gasket. I can't see how this would ever be possible on my car - there's no gap at all on the rear edge of the glass (adjacent to the fixed window). If I lower the window about 2" and try to adjust it in the frame (grab the upper edge and try to "twist" the glass to raise the left side and lower the right side), it appears to be solidly in place in its tracks.

I've ready many posts where people complain of the cruddy design of these units - comparing them to the front windows I can see why.

Any suggestions?

Well - and darn-it, too - it's not the regulators. The motors are kaput. The passenger window started making the same popping noise at roll-up that it did before I changed the regulator. Pulled the motor and used a pair of pliers to securely hold the gear while a friend toggled the switch. On down - no slippage at all. On up, easy to make the gear stall and pop-pop-pop.

It's frustrating that these units aren't user serviceable. On my two previous cars (both Lincolns - 92' Mark 7 and 93' Mark 8), when the motors quit, you could pay $200 to LM for a new unit, $85 to the parts house for a rebuilt unit, or for about $5, you could buy a gear kit and rebuild the factory unit yourself.

I'm looking at some remanufactured units from Cardone - $76 at AutoZone with limited lifetime warranty. Since they're so easy to replace, I figure it's worth the "risk" of having to replace them again in a few years.

Here in Houston, it's rare that the weather is comfortable enough (for me) to actually need to roll all the windows down anyway.

Thanks for the interest.