I did a conversion on a W124 from R12 to R134a, and I had to do it twice in order to get the same cooling efficiency I had with R12.

The second time around, I changed both the condenser AND the A/C fans (from single to dual) to the versions used with the FACTORY designed W124 R134a A/C (already did hoses, expansion valve, dryer, and A/C compressor).

Since R134a is NOT as efficient as R12 (all things being equal, e.g., using the existing condenser, etc.), you will need MORE airflow (esp. when not at speed) to get the cooling efficiency you had with R12.

:-) neil
1988 E36T AMG
1993 500E