my car had the exact same problem with both power seats....
it either works perfectly, or doesn't respond at all... but if I turn
the key, then it works(or not).... It's been driving me crazy
for the last couple of years.

Yesterday, I decided to finally do something about it...

I found this thread and followed the advice. Bought the K24 relay at my
local Mercedes stealership for $42(!)... . Another dealer 10 miles away
sells it for only $34, but I didn't feel like fighting the morning traffic, drive
the 20 miles roundtrip, just to save 8 bucks...

The strange is thing is that as soon as I showed the parts guy the original
relay that I brought, he said "power seats don't work? we sell dozens of
these relays every week..." B In fact, he immediatlely reached under
the counter and pulled out a new one from a box of perhaps 20 of these
relays... Based on his comment and all the people who posted about this
problem, it is clear that the relay had manufacturing defect or a design
flaw. Clearly, Mercedes and Siemens must also know about this. There's
no possible reason for a relay to go back after less than 10 years.
(maybe on a Jaguar, but definitely not a Mercedes)

Anyway, I just came home' and plugged the new relay in....
THE SEATS WORK PERFECTLY NOW!


THANKS!!!