I've just purchased a 2000 CLK430 Cabriolet and the a/c doesn't blow cold. I've run the HVAC diagnostics and came up with the following values. Could someone please help diagnose my problem? The previous owner says the car needs an a/c sensor, but doesn't know which one.

Note: I do not have any DTC codes (the display read E FF).

These codes are for the various sensors I believe:

1 - 122
2 - 115
3 - 124
4 - 124
5 - 125
6 - 20
7 - 0
8 - 127

Does the 0 on sensor 7 indicate no R134a? Should I simply add a can or two and try again?

Please advise. I great appreciate any help!
M-