1979 C10 Restoration problem.

[Jrwhit]

New to auto HVAC and could use some advice. My system is R12 with rebuilt A6 compressor, new condenser, new compressor hose assembly, new liquid line, new accumulator / dryer, new orifice tube, removed flushed and cleaned evaporator core. Upon system assembly, I added the total system requirement of 10 ounces mineral oil to compressor, knowing the rest of the system was dry. After evacuation, I am able to charge with a little over a pound of R12 to accumulator (low side) to around 160 psi R12 static pressure low and high side. With the engine running and compressor cycling, the low pressure side is not dropping to allow more R12 to be added. The total R12 system charge is 3.75 pounds so I know I am low on refrigerant. Also, during compressor cycling, the high pressure side is not increasing while the low pressure side is not dropping both are staying around 160 - 170 psi. Downstream side of orifice tube is frosting and slight cooling out of dash registers, but evaporator output line is warm and accumulator is warm. When removing old orifice tube it was difficult to remove due to evaporator tube deformation and old orifice tube screen had a lot of black ( and magnetic) debris and looked mostly clogged which is why I flushed the evaporator before reassembly. Upon reassembly, new orifice tube had a tight fit into evaporator tube, again probably due to afore mentioned tube deformation. I tried to straighten tube to get best most free orifice tube fit when installing new orifice tube. So, I'm wondering if I have too much restriction at the orifice tube, insufficient refrigerant charge preventing good refrigerant flow, or a compressor problem. My thought is to change the evaporator core first. I would appreciate you guy's thoughts on my situation.

 

[CountKrunk]

Following along.

My gut says the evap isn't working properly. Everything else is brand new right?

 

[NLD79K10]

160 psi is pretty darn high for static pressure on an R-12 system unless you're over 120F under hood, at 70F I'd expect a static pressure of around 70psi.
Your system seems severely overfilled if you ask me.

 

[Jrwhit]

What about the orifice tube oring not fitting properly in the evaporator tube? I'm wondering if the evaporator tube may be a little out of round and the oring on the new orifice tube may not be sealing to the evaporator tube ID.

 

[Jrwhit]

I forgot to mention this is Texas and the temperature is around 105*F. The under hood temp could actually be around 120*F.

 

[NLD79K10]

Sounds like the evaporator isn't doing what it's supposed to. I'd have dumped the old evaporator and put a new one in rather than flushing it if there's a load of crud in the orifice tube screen and it has a deformed tube on it. If you're replacing everything else, the additional cost of a new evaporator isn't going to bankrupt you, but it would save you headaches like this. If the evaporator is leaking enough refrigerant past the orifice tube o-ring, the pressure drop is going to be too little to cause the expansion of the refrigerant needed to extract heat from the air passing through the evaporator as the refrigerant will try and go through the path of least resistance.