My 2nd O2 sensor is STILL bad. They just ordered the part last week so I am taking it in tomorrow to finally get fixed. Well I was wondering, is that the reason I am getting much poorer gas mileage? I just filled up today and I got 260 miles to my last gas tank of 16.4 gallons. That averages to just over 16 mpg... not good! When I have my A/C on, does the compressor shut off above a certain RPM? I know that it can damage the compressor by flooring it with the A/C on. I want to know so that I don't demolish my compressor! Also, how long do you think that compressors last on average (made in 1995). I live in an average climate where the temp is almost always between 50 and 85, So Cal. Thanks guys.

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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!)

The C-class A/C compressor is the BEST that MB has used. Very few failures due to the fact that it always runs. IT is a variable displacement compressor, so instead of turning on & off, the pressure determines the travel of the pistons. MUCH better than all other models as far as replacement percentage is concerned.

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
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MBDOC, thanks for the info. That is good to know. What do you mean it's always on? Is it ALWAYS on? Whether I have it switched on via climate control or not? Why is that? So when I punch it with the AC on, it just reduces the cooling capacity instead of turning off? INteresting. Makes me feel a bit better knowing it should have a long life.

__________________
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!)

Also,
Anyone know about the 02 sensor and gas mileage?

(BTW, mechanics say my new 02 sensor is STILL not in, ugh... CE light has been on for close to two months...)

__________________
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!)

Unless the "O" off button or the "EC" button is pushed the compressor should run.
The second O2 sensor is a monitor for the catalyst, shouldn't have much affect on fuel mileage!

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator