68 Vette Cycle Issues

[dntoearthman]

I installed a new Sanden compressor, parallel flow condenser, new evaporator and insulated heater box , hoses, drier, Expansion Valve, and a POA bypass valve with cycle switch.
All the vent controls and fresh air and valves have been rebuilt as well.
MY issue is it cycles to often and takes a long time for the compressor to come back on, my LS pressure is just to low I suspect for some reason?
I don't know if this means anything but when I turn the system off it takes 25 minutes for the system pressure to balance out.
I installed another new Expansion Valve thinking this was the problem, Another new cycle switch as well.
Could a faulty drier cause any of my issues?

Here are some readings:
Recharging the system after full vacuum:

23.3 OZ
83 deg Amb
LS = 10 PSI
HS = 165 PSI
Vent temp = 43 Deg

23.3 OZ
90 Deg Amb
LS = 12 PSI
HS = 180 PSI
Vent temp 42 Deg

39 OZ
90 Deg Amb
LS =16 PSI
HS = 200
Vent Temp 43 Deg

In Garage:
The only time the LOW side goes up is if the AMB temp Exceed 95 deg and or my electric fans are not on.

Electric Fan on with External Fan, raising the RPM up to 2000 RPM the LS pressure will drop below 8 PSI – this is with cycle switch bypassed and it will freeze up the LS lines.

I have the cycle switch set to go off at 15 PSI now because at 20 PSI it will not keep the compressor engaged, The car spends more time with the compressor cycled off than engaged, It takes several minutes for the LS pressure to go up enough for the cycle switch to re-Engauge the compressor.

Road test:
It cools relatively well 45- 50 deg vent temp but the compressor cycles way to much its off more than its on. The vent temp will get up to around 65+ Deg before the compressor re-engages.

Thanks for any advise.

Mike

[dntoearthman]

I just found a NOS POA valve, once installed I'll post back. From what I have read I can not recommend anyone trying the POA bypass kit.

Thanks Mike

[JohnHere]

To me, it sounds as though a couple of issues might be in play here. One is an incorrect charge (too little refrigerant), and the other is an incorrect TXV (when used with the POA eliminator).

When you install the NOS POA valve, check the under-hood decal for the original amount of R-12 it called for. My guess is that it was about 52 ounces. So an 80 percent charge of R-134a would be around 42 ounces, which is nowhere near the 23.3 ounces you charged originally and still more than the 39 ounces you put in after that. This assumes keeping the TXV you have in there now.

[Dougflas]

Early Corvettes were a hard vehicle to keep cool. If I were you, I would keep it original and keep it R12.

[Dougflas]

If my failing memory is correct, the POA has an oil bleed line on it. There is a shrader valve in it that is SPECIAL. Do not use a normal replacement.