Yes, when I have REST on I can hear it click every few seconds. THat seems to be your problem, but is the Rest light illuminating.. or does the PBU let you know that it's on? Does heat come into the cabin also?

Interesting... I don't know why the DIA is not working on your car... I got the info from a 96 202, and that climate control is more similar to yours (maybe just aesthetically). Steve... can you help us out with this??

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2006 E350 w/ 155k miles (Daily Driver)

Previous:
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)