kompressor m271

I have a problem with the heater not getting warm,the AC seems to be fine and have changed the air filter,should my next stop be to change the thermostat? it a 55 kompressor,thanks.

Got a late 2004 W203 M271 Kompressor and think the Supercharger is starting to groan a little. Looking at changing the oil but on removing the oil fill/drain plug I'm unable to get the suction pipe to go far enough into the supercharger to suck the old oil out so not sure how the various guides...