'99 F250 Super Duty- immediate low side drop

[Tim]

The liquid line to evaporator was 46 degrees and the evaporator to accumulator was 43 degrees. I took both measurements about an inch from where the lines go into the HVAC box.

Give or take the coil temp and vent te,p/ Should have around 40-degree vent air. Next is to find out why you are reheating the evap air before to reaches the vents.

[69DropTop]

Next is to find out why you are reheating the evap air before to reaches the vents.

Ok, so do you think the in/out temps seem right and the pressures seem right? I guess you think that heat is getting introduced back into the cool air somehow/somewhere? I didn't get a chance to last night, but I can try pinching off one of the heater core lines to see if that makes a difference.

[69DropTop]

I pinched off one of the heater core lines with a set of vise grips then took the truck out for a spin. I got 42 degree air out of the vent. I removed the vise grips and the temp went about by about 8 degrees So, I guess that answers the question of why the pressures and everything seem right but why I wasn't get as cold of air as expected.

I'm guessing the foam that seals the hot/cold air mix door in the heater box is shot. I was thinking of looking around to see if there is some type of manual shut off valve I can install in the heater core line or maybe install a vacuum operated water shut off valve like my '69 Cougar has that is activated when the A/C is turned on but not sure there is a vacuum line I can tee into that is only used for when the A/C is on. Anyone have any suggestions or other ideas?