CHEVROLET 1500 CLIMATE CONTROL

I Checked All Fuses First, All Good. Put On Gauges, Engine Not Running 75 On Low Side, 75 On High Side. Start Engine A/c On High, Clutch...

On My 1991 C1500 My Ac Cools Good On The Low And Medium Blower Settings. The Problem Stars When I Turn The Blower On To The High...