73 Charger How much a/c expansion valve insulation needed?

[WH23G3G]

So I had some tuning done on my Charger today and we vacuumed and recharged the a/c system. It held vacuum, no leaks. vacuumed for 15 minutes and it held pressure. We charged the a/c which was starting to get cold while we were charging it. Then when we drove it around it was hot like heater. The mechanic thinks the water valve maybe stuck open or the expansion valve stuck/or not insulated well enough. He said the sight glass shows clear and means a full charge. We put 3 can of r134a and 10 ounces of oil as stated in the instructions with the a/c compressor. Using a complete factory system but all new stuff. New hoses, evaporator, expansion valve, switch, harness, clutch, drier, and condenser. It's been installed for a couple years now but not opened up to the atmosphere just hadn't been charged because of tuning issues. Now the engine seems to be doing ok I want to get the a/c working right. The compressor and clutch comes on and runs nice and smooth. The mechanic said the pressures were right on when he was charging it. I know there is suppose to be some kind of insulation wrapping over the big expansion valve hose. I still have the original foam wrapping over it but I don't know if it needs more. What can I do to determine the problem? If the car runs as good as it did today after my mechanic did the tuning I'll look forward to driving it but would love a/c with it.

[Pete in NH]

Hi,

The first thing I would check would be that heater control valve. A simple way to do that is to use a C clamp to squeeze a heater hose closed. If things get cold again you'll have your answer.

On your A/C system, You can not charge R-134A by the sight glass as you can R-12. If you have three cans of R-134A in there that is about 36 OZ. Which is the original R-12 charge, you may be over charged. With R-134A you usually use something less than the full R-12 charge especially if you are using the original serpentine condenser. With a serpentine condenser the discharge pressures can get quite high when the system is operated in high ambient temperatures. For this reason a high pressure cut off switch should be installed as part of the R-134A conversion. The R-134A charge is usually something like 80% of the R-12 charge. Also, make sure you have the original radiator shroud in place for maximum air flow through the condenser.

You mentioned normal pressures. What were those pressures, at what ambient temperature, engine RPM, and blower speed?

The foam insulation should be over the part of the suction line where the sensor probe for the expansion valve fits into its well. I suspect your issue is going to be the heater water flow.

[WH23G3G]

Well the full charge of r12 on this year was 2lbs 14oz. So that in r134a would be 46 ounces. It should be close to the right charge. I just checked it real quick tonight, I didn't hook up the gauges yet. I mainly wanted to see if the engine started easily. And it started right up on the first try with no pump to the gas pedal. So I let run about 5 minutes with the a/c on. I checked the temp of the low pressure hose by hand. It got cold real quick on top of the compressor where the large low pressure line bolts to and then back at where it screws into the expansion valve it was cold. But it still felt like heat coming out of the vents. I tried a/c and max a/c positions. I'll try and check the pressures tomorrow. I bought an NOS heater valve for like $125 like a year ago. I know there was two different versions in 1973 for a/c cars. The rounded two piece one and the cadnium plated version that was released later in the year which seems to be the one still available at the parts stores. Is this one http://www.rockauto.com/catalog/moreinfo.php?pk=815513&cc=1079524 easier to adjust and setup? How do I know if one of the doors is closed or open when it shouldn't be? Or if the expansion valve is not working?

[Pete in NH]

I shouldn't try to math in my head too early in the morning. You are correct on the R-12 system charge and the R-134A charge is about right as you said.

From what you said about the suction port on the compressor and suction line getting cold, I think you're right about the heater control valve and water flow through the heater core.  Again , I would try clamping a heater hose closed or disconnect the control cable on the heater control valve and make sure it is closed manually. I suspect you're A/C system is working correctly but is fighting the heater. I would not worry too much about A/C system pressures right now, they were just something I was curious about.

[WH23G3G]

So how do I know for sure this water valve is closed? This was an NOS one correct for my year and production date. The Chrysler service instructions for installing and adjusting the cable is vague and illustrations are worse. I cannot figure out how the loop clip goes on the end of the cable at the water valve end. I lost it anyway. Is the aftermarket gold water valve an easier to adjust and install option? I tried manually pushing the cam lever both ways to see if there was a difference in outlet vent temp but it's like straight heat no matter what. When I switch from MAX A/C to A/C I can hear the doors open/close but I can't actually see the doors move so I don't know if all the proper ones are closing/opening.

[Pete in NH]

My 71 has a vacuum operated valve rather than the mechanical cable so I don't know very much about the specific adjustment procedure. To check if the valve is open when the engine is warmed up if both heater hoses are warm/hot there is water flowing through the heater core and the valve is open.

Being a NOS valve and likely quite a few years old, there is a good chance it is no long able to seal closed. You might want to try a new aftermarket valve. I've had an aftermarket valve on my 71 for many years. The original style valves with those plastic bodies eventually cracked and leaked. The aftermarket ones are all metal.

[WH23G3G]

So I clamped the small 1/2 hose on the water valve and started it up and it was cool. As soon as I unscrewed the clamp it was already hot even though it had only been running 3-5 minutes but you could definitely feel a temp difference. So does that mean the valve is bad or could hoses be hooked up wrong?

[Pete in NH]

I don't think there is a way to hook the hoses up wrong unless you don't have the water control valve in the loop at all. I would say the valve is not closing and is bad if things remain warm regardless of the control valve position.

[WH23G3G]

I bought the new aftermarket heater valve today and installed it. It seems to work. I couldn't hook up the heater control cable because I could not figure out how the bracket mounts to the fender under the hood or even if it will mount. So it's just hanging there but I don't think it will go anywhere. I'd like to see someone who has a 73 or 74 Charger with this aftermarket heater valve properly installed so I can properly place mine. It definitely doesn't go where the original valve goes. It's a whole lot easier to work even if you have to do it manually. You can just close the lever and it feels nice and cool. And then when you open the valve it's hot. I just have to ride it down the road now and see if it's working really good. It was cold just sitting there idling but not uncomfortable cold but then again I was sweating too so that's why I need to test drive it to see if it really gets ice cold inside. The blower motor isn't all that powerful, the same way on my 65 Valiant. It does change speeds just not as powerful as say my 1998 Ranger. I tried two resistors I have too but I guess it's just not a powerful blower motor. I replaced it during my resto when I had the plenum box out for rebuilding. But yeah if anyone has a 73 or 74 Charger with the aftermarket heater valve hooked up and mounted properly I'd like to see because I can't figure out how it bolts to the fender.