W210 E420 repeatedly blowing fuses 7 and 4, it's not the blower
 

As the title says, I keep blowing out fuse 4 and fuse 7 immediately on putting the key in position 2.

If fuse 7 is left dead and fuse 4 is replaced, it stays alive -- fuse 4 only dies with fuse 7 but not alone. I unhooked the whole blower motor and resistor/regulator assembly from the harness, same behavior. I removed and unhooked the automatic climate control module and the behavior stops. If I plug in only the left plug of the automatic climate control, the fuses do not blow. If I plug in the right plug it blows. I bought a replacement climate control unit and the behavior is unchanged.

Nothing new happened to go from fine to the current state, that I am aware of. It was working fine when I parked it, and the next time I drove it (this is my daily driver so it was a few hours later) it started the behavior outlined above. I had a similar behavior about a year ago (fuse 7 blowing) that I did not document or study extensively but it was resolved by replacing the automatic climate control module. This time that did not seem to help.

There's not a lot of other stuff on this circuit so I'm unsure how to proceed.

Try unplugging the auxiliary water pump.

just tried that, no change in fuse blowing.

bump for fresh ideas

bump