Mercedes W220 Climate Control Read Out Fault Memory And Erase Fault Codes Turn the key to the on position. Turn the a/c switch on. Both AUTO buttons should be pressed out. Push and hold both the charcoal filter button and REST button at the same time and release. You should now be in diagnostic mode. Scroll through the faults using the left temperature selector. To delete the faults press in the left AUTO button and then press in the right AUTO button then press out the right AUTO button and then press out the left AUTO button. The display should show “deleting fault codes”. Thanks for the input - still having problems but greatly narrowed nown as result of your help. Tried to add 134a this am, wouldn't take any. leaning toward the evap temp sensor, as Item #50 on diagnosis indicates that the Comp unit is off -recei8ving no power. I located the speciific diagnositc proceedure for the 1997-1999 C280 Thought some of you may be able to use it...