I do not know for sure about grey market but why would it be any different?
The circuit is designed for the Driver's front and the Passenger rear on the same circuit and vise-versa. if both of the rear windows do not operate, try the lockout switch on the center console and see if it is hooked up. That is what it is designed to do: keep little ones from opening the rear windows.
1985 500SEL (260,000 miles) SOLD!
1974 280 SOLD!
1994 Volvo 850 Turbo Wagon (Yuppie Ice Sled)
"I know I have a Benz and they know it too." If you start bragging about it or shoving in people's face, you then become a Wally; especially to the girls.