I recently recharged my A/C system in my 94 e320 (r134a) because the system was low on refridgerant (but not empty). I did not vacuum the system and it was never opened to the atmosphere (no component replacements). Here is the trouble: the A/C system doesn't blow cold in the city, stop/go traffic, or even at 30-50 mph moving. The A/C works great on the highway (65+mph) it blows ice cold after about 5 or 10 minutes at that speed. Unfortunately I no longer have access to the set of R134 gauges that I used to do the recharge to double check the low/high side pressures. Any suggestions on troubleshooting before I purchase a set of gauges? I have heard a few things about the mono valve (or heater valve) but don't know how to test this part out or what the symptoms of a bad part are. Thanks!

Edit: My aux fans are working on both stages, I just replaced the fuse on the low speed relay and double checked their operation. It seems almost as if the condenser has slight blockage and only cools at high speed (when there is more than adequate airflow)??