Hi Charlie ..

Try repeatedly depressing the large rocker switches on the
outside of the climate control panel it's the one
with the small red LED on top .. If that doesn't engage
the 'auto' mode try simultaneously depressing the temperatue
direction keys ( blue and red ) .. this is supposed to
put the climate control system in auto with a default
temperature of 72 degees ..

I've found that the climate control behaves best when in
'auto' mode .. I leave mine @ 65-67 degrees and with
the fan on at the 2nd level .. ie two 'bars' blacked
out on the fan digital display .. and I rarely adjust/fool
with it once setup ..

Couple of other items to check ..

Make sure you use a MB approved synthetic oil ..
I use Mobil 0w-40 year round and check your
coolant to be sure it's 'orange'.. no 'green'
stuff in this model please

Run your rear passenger windows up and down on
a regular basis to give them some exercise ..
The regulators seem to 'break' with lack of use ..


What color combo did you get ??

Jim in CT ..