Help with Mercedes Benz Seat heaters

i have 2005 Benz E320 CDI. Heated front seats and steering wheel. 25A fuse in left side dash fuse panel blows and takes out power to both front seat heaters and heated wheel. Replace fuse, wheel and passenger heaters work fine, circuit blows fuse if drivers seat heater is turned on. Replaced the heating element in the drivers seat (it showed a short when tested) yet same condition exists. Can someone help? Where are the relays? Any other ideass?

Bob