If the compressor comes on & goes right back off then checking the compressor speed sensor would be MY next step.

All testing should be done at the klima relay connection, relay removed.
The speed sensor MUST generate at least 0.3V a/c at idle (650-750 rpm) with the compressor running.

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator