With the windows, I cannot stress enough that you have to keep the window tracks clean and free of debris and make sure everything is sliding properly. Many people see the regulator is bent and throw in a new one and get pissy when it fails 3 months later. The regulators will warp because of the lack of stop switches but more often it is due to lack of proper lubrication and other parts in the system that have to be cleaned, lubricated, or replaced. My brother has a set of Chinese-made aftermarket regulators in his front doors on his W116 and they have performed flawlessly because he took his time to get the windows moving properly before installing them. That being said I have seen brand new OEM regulators that are already starting to warp when they are still sitting in their packaging.

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Current: 1975 450SEL, 83 300D, 88 Yugo GVX, 90 300D OM603 swap, 91 F150 4.6 4v swap, 93 190E Sportline LE 3.0L M104 swap, 93 190E Sportline LE Megasquirt, 03 Sprinter, 06 E500 4Matic wagon.