First, have you discovered the forum right below this Forum called "Diesel Discussion"? I just happened to click the wrong link and noticed some posts I thought I'd check out.

Second, .. . the most common reason for fuel leaks, or the first thing to wear out are the return lines which are made out of hose/rubber material. Over time, they get brittle and start leaking and pooling at the bottom of the head. I would suggest buying a length of the proper OEM hose, remove, measure anew, snip and replace. I would replace all of them, even if only one is leaking, as the others are sure to follow. Similar to replacing coolant hoses . . . [don't do like my ex-husband did and replace one at a time, one every month and having to pay the cost of coolant replacement each time.!!!!] Then do your normal bleeding of the system. Unless you observe the injector leaking, or a leak from a crack on the tubing, or crack on the tubing, I would say go straight for the return hose, especially if it's pooing below it.

As for the AC question, you are just as likely to get an answer in the Diesel Discussion Forum, even though the AC systems may be identical between the E and D models.
Sorry I cannot help you with that problem, but I would look for a reason for less power going to those wires, then replace the entire system. . . . sorry, just don't know enough about it.

Torie

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1983 300D, the "Avocado"
1976 240D, 4-spd the "Pumpkin", SOLD to Pierre
1984 190D, 2.2L, 5-spd, my intro to MBZ diesels, crashed into in 2002