I have a 1997, SL500. The A/C is stuck in EC mode (light on). I have read quite a few threads about running the A/C diagnostic program. I turned the key on, set the temperature to 72, hold the Reset for 5 seconds. I can see the 1 and 78 flashing alternately. I assume that is the in-car air temperature.

I can't go up or down to display any other number. I have the single temperature unit. I tried the Auto button, up/down button, defrost etc.. Nothing seems to work. Is my unit defective or I was just pressing the wrong button?

Thanks
Bob

Try the blower + and -.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

OK that works using the fan +/- button. Here is what I got:
1 - 75
2 - 67
3 - 73
5 - 73
6 - 80
7 - 4.7
8 - 71
9 - 37
10 - 125

According to http://pages.prodigy.net/jforgione/MB_AAC.html
I don't see anything wrong. The AC system shows about 85 psi on both high and low side without compressor ON which is about the same as #7 (4.7 bar). Is this number (pressure) too low which causes the EC to be on all the time?