How can I visually tell if the AC compressor kicked in for 2003 SL500?
Does this model AC compressor have the clutch that can be turned by hand?

The reasons for my questions were that I can’t turn off the “AC off” lamp at the climate control, it will blink slowly three times and keeps stay on, I am still not sure of the problem, but this may have caused the AC compressor not to kicked in. I have been trying various setting but have not able to turn the “AC off” lamp off.

I tried to spin the AC compressor clutch (not sure if that is the clutch, the center of the AC compressor pulley) by hand but it didn’t move, but I can see it spins with the engine when the engine is running.

There is no error code read with the OBD II, with engine running or just key ON.

I have check both AC LOW and HI pressures when engine running and while engine not running and there are no different in pressures, both LOW and HI stay at about 45 psi. This also indicates that the AC compressor is never kicked in, right?

Any suggestion that I can beside take it to the dealer?

Regards,
Hung