Roof A/C

[bigray]

Hello All,

Last weekend I ran my A/C from about 4 PM to 7:30 am. At 4 it was really hot so I had it on full blast. As the evening progressed I was able to turn it to low where it remained throughout the night.

When I turn it back on around 8:30 or so, some pea-sized ices was blowing from the unit.

1) Is this normal?

2) Has anyone added refrigerant. Does the roof A/C (Duo
   Therm) require R-12.

3) And has anyone converted it to Freeze-12 or some other alternative.

4) When not using the dash air, does your roof A/C cool the entire rig.
   Mine does not. I have changed and reenforced my doghouse insulation
   but I still get alot of heat in the cab.

Thanks for your help!