89 a/c low pressure line freezing up
 

My low side is freezing up. I did replace compressor couple months ago. Changed orifice tube and pulled a vacuum. What causes line freezing?

Low Pressure Switch should open at 25 psi to prevent the ice (assuming it's still R12). It's either defective or needs to be adjusted. There's a screw between the terminals of the switch. Turn it clockwise to raise the cutoff threshold. To check it out, hook up your Manifold Gage set and put the a/c on Max. Pull the Blower Motor connector and the pressure should drop. Note the low side pressure when the compressor cycles off. Remove the Low Pressure harness from the switch and turn the screw a 1/2 turn and recheck. If it doesn't change anything, get a new one. Note: the new Switch may be set for R134 which is a 22.5 psi threshold. That's too low and it will have to be adjusted to 25 psi to prevent the icing.

Its still r12. I will check the #'s and that switch and post findings! Thxs!