Automotive airconditioning experts...Help!?

My 91 Ford Ranger AC will not discharge cool air after about 10-15 minutes at Idle or in traffic.I’m not sure if the clutch shut off.I checked suction pressure…it was 35# (R12). Don’t have a 3/16 fitting to check head pressure.My Condenser is a little bit dirty.Any ideas? At idle after running for 10 minutes the clutch disengaged and would not come back on until the car was off for about 15 minutes…

Not an expert, more like an automotive airconditioning schmuck, but my WAG is that the fan clutch is going out. This would keep the condensor from cooling, which would cause it to cycle off.

No fan clutch…fixed fan. The clutch I was referring too was the compressor clutch.Thanks anyways