Any insight/advice would be greatly appreciated! I’m about at my wits end and ready to order a Vintage Air system for this 1979 C3 of mine, but I would love to find the reason why I can’t get my AC to cool, even if I decide to go that route or not.

I purchased the car knowing it had a blown AC compressor from my friend. Air did not work for a few years as the compressor had seized up and he just cut the belt. I ordered a new AC Delco gold compressor, orfice valve and a new accumulator and installed them. Another friend had R12 stashed away and so I left the system using R 12 Freon. I evacuated the system and it actually held vacuum of 29 inches for three days before I blew in the charge so i totally positive I have no leaks.

Ran car and it blew hot air through all the vents. I then traced down and replaced the heater control valve. In fact, I used a four seasons heater control valve part number 74781 (in photos) which I saw recommended on the number of sites. I decided to use this because it totally bypasses the heater core and routes water right back to the engine block instead of even allowing some hot water to get into the core like the original control valve does . I have vacuum to the valve and the valve opens and closes. I also rechecked my AC pressures and they seemed just a little low so I ended up adding in one additional can of Freon. At 90° I’m running 23 pounds on the low side and about 225 on the high side.

I then found that I didn’t have high-speed on my blower fan and that was a bad heater blower resistor which I replaced. I also know that I do have vacuum to the heater control valve because I can actually see the valve opening and closing when I put it into AC mode and off AC mode. No I didn’t measure how much vacuum, but it is fully closing the valve in A/C mode so that heater water completely is bypassing back to the engine and not into the heater core.

I still have hot air coming out of my vents! I’ve searched and searched the Internet, but can’t seem to find any other suggestions. The Compressor clutch is engaged. The pressures are good. Vacuum is at the new heater control valve… Does anyone have any other ideas of what I could or should look at before I just decide to pitch it all the way out and spend a lot of bucks for vintage air system. Since I live in Arizona, you need to have air conditioning 10 months of the year or I can forget driving the car. Any help would be greatly appreciated for me to go track down before I give up.

 

does the compressor run and you still have hot air?
what are vent temps?
does your recirc door close when in max setting?
I would use shut off valves to be sure no water into core.

 

With those pressures and the fact that the system took in a full charge of R12 that is mystifying that you get no cool air. Only thing I can think of would be the evaporator box is jammed full of debris.

Does the suction pipe (the big one) show condensation???

VS

 

Blend door cable adjustment. Door not closing completely

 

Prowlrman
Just a couple of ideas to throw out:
I would totally eliminate the potential hot water by looping that back itself..... just to take it out of the picture. I do like that 4-way valve quite a bit too. Try that and then if it doesn't help I'd do a cleanup of the box as mentioned in post #3.
If, after doing those 2 things you still don't get cold air then spray a hose on the condensor while the a/c is running to see it helps with heat exchange..... assuming your fan clutch is in good shape it should be drawing adequate air in to support the a/c operation.

 

It doesn't look like you have any insulation around the orifice valve, so is the evaporator inlet and outlet getting cold? (ideally measure the temps, but you can just put your hand on them to check) If so, then either there is little or no air passing through the evaporator, or your blend door is not closing as has been mentioned above.

 

The low pressure line coming out of the compressor should be very cold to the touch and sweating like crazy if your ambient outdoor temperature is upper 80's to 90's. If not you may have a defective compressor out of the box.