What's happening to your engine coolant temp gauge when the A/C stops blowing cold in city traffic? Does it get dramatically hot or only moderately warmer? Both your clutch fan and your auxiliary fan must be operating correctly to keep engine temps under control, and that helps make the A/C more effective, too. That's not to say that you may not need to add refrigerant, only that proper airflow is needed for proper A/C function.

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1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't