Factory ac system. Low pressure line freezing. Refrigerant is at proper level???? Also is there any easy way to increase the ac / heat fan speed??
If the low side is freezing, it's probably a restriction or TXV. Need to know what your pressures are. With the gauges does the low side pressure try to pull down to zero or even a vacuum before cycling?
For the fan, try and adapt a late model Caravan dual blade fan. Those move a monstrous amount of air. Spinning the old fan faster is going to have limited results. And get a OE fan! The aftermarkets have really bad blade designs and don't move much air but make lots of noise!
