[70 SS 454]

my system was rebuilt in 2006 using NOS POA valve
system is all GM except the new hoses & R-12
used to run 38* duct temp right after the rebuild


this summer it is running about 45* duct temp during day with ambient 93-100*
pressures are 30/250 with engine/rad warmed to 170*

drops a few * to 40* if driving (better airflow thru condensor ) at cooler nite 83* temps

what should the operating pressures be?
i know the POA is calibratetd to hold 29 psi but dont know if the operating pressure should also be 29 ( if so i am only 1 psi high at 1500 rpm... goes to about 33 or 4 psi high at idle) but i dont knw that the actual operating pressures should be.

anyone know for sure?? for a stock GM system???

TIA

 

[twotone64]

you will actually need to take temperatures 6" in front of the condensor. This temperature will tell you what the High Pressure side should be. You will also then take the temp (which you already did) of the air coming out of the vent closest to your evaporator (you should actually take the temp of the evaporator but it is not redily accesable. Again these temperatures will correspond to specific pressures on your guages. You can go here to see what your temps/pressures should be.

http://www.ackits.com/aacf/ptchart.cfm

 

[JAYARTER]

Greetings from Arizona
It sounds like its about right, Are you using R-12 or R-134? I just did my 67 Elcamino, all new parts except POA valves are no longer availible, there is a kit that you can put in that looks UGLY! My friend who does AC for a living helped me out. We installed a POA valve that has been machined internally and has a orfice tube instead. working great with 45 degree air in our 100+ temps. And the best thing is it looks 100% stock. I'm using R-12 Pictures on photobucket. Have a good weekend....Jay

 

[Ark68SS]

what should the operating pressures be?
anyone know for sure?? for a stock GM system???

From the Service Manual--
Doors and windows closed, car in shade, hood up, in neutral or park with engine at 2000 rpm.
A/C controls set on MAX, high blower speed
Thermometer placed in front of grille and another in the right hand vent.

Temp of air entering condenser, high side pressure, evaporator pressure @ POA, discharge air temperature @ RH outlet

70* 160-170 psi 29.5-31.0 psi 41*~44*
80* 195-205 psi " " " 42*~45*
90* 220-230 psi " " " 44*~47*
100* 270-280 psi " " " 45*~48*
110* 300-310 psi " " " 47*~50*
120* 345-355 psi 29.5-34.0 psi 51*~54*

BillL

 

[LeoP]

There is enough explaining in this post, the temps and pressure are in the ballpark.

 

[lsrx101]

I agree with the others who said that the pressures look good.
However, you could be getting some reheating of the air via the heater core, if the foam seal on the blend door has disintegrated. It's common unless the suitcase was removed and resealed.
Also, if there is a coolant shutoff in the heater hose, you need to make sure it's working correctly. If not equipped, adding one can help drop the vent temps a few degrees.