I have a 300SD built Oct 83. It has a 500mA draw on the battery that will flatten the battery if you don't drive it for 4 or 5 days. I traced it down to something associated with the power seat circuit. The draw goes away if I pull the relay associated with the power seats. There are two of them one is labeled Isolation relay or some such. I pulled the one closes to the center of the car. I thought maybe is was a sticking relay but I swapped it with the aux fan relay but same problem remains.

Any ideas?

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98 E320 4matic Wagon
84 300SD (2 ea.)
51 Chev 1-ton PU
Assorted old motorcycles

Do you power seats get power when the doors are open and the ignition is off? Maybe the circuit is staying energized all of the time.

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1989 300CE

The seats do get power when the doors are open with key off. I don't think they have power with the door closed but I'll check to be sure.

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98 E320 4matic Wagon
84 300SD (2 ea.)
51 Chev 1-ton PU
Assorted old motorcycles