1979 Ford F150 A/C not cooling
I have a 1979 Ford F150 1/2 ton P/U XLT, 4WD 6.6L 2BL OHV 8cyl that I'm trying to put A/C back in. The truck had factory air, but the evaporator is the only original part in this setup (along with the controls inside the cab on the dashboard).
The new compressor is working. All the pressures look good (the low side is around 35 to 40). But we're finding that the air out of the vents is only dropping 20 degrees max. We've checked to see if the blend door was not working and it was getting heat from the heater core. We blocked off the heater core completely with the same results. It just doesn't seem to be getting cool enough. The large fittings on the firewall should be cold (maybe 40 degrees), but it's only cooling to about 79 degrees, about a 15 degree drop.
We cannot see into the evaporator box to see if there is an expansion valve in the system, but we did not put an expansion valve in with the new system we put on.
Any advice appreciated!