I had the same problem of yours and have solved him!
I have cream beige leather seats and my driver seat don't heated up...
You have to unmount your seat completely and separate the metal and the cushion, to access to the pads.
This guide will be helpfull for everyone here!
http://www.omegaowners.com/forum/YaBB.pl?num=1192830810When you have the heated pad before you, check the wires connection that entering in it... I'm sure that you will find at least a burned one... You just need to re-sold it (may be using a little piece of new wire, same size that those used for speakers...).
You will need A LOT of time and patience, and you need to be VERY carefull, but the job can be done! Mine heat again now and it's a pure happiness when it's -7°C out, I just hope that will last long

For the leather seats, the heated pads are stitched with the leather, but it doesn't matter for repair it!
CHECK THE PAD ON THE SEAT FIRST!!, that could be saving your time as I'm pretty sure that the heated pad on the backrest of the seat is OK!
Unfortunatly I don't have made pics...
Hope this helps
