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freezing poa vavle and suction line

modicab on Wed September 26, 2012 9:18 PM User is offline

Year: 1969
Make: chevy
Model: chevelle
Engine Size: 396
Refrigerant Type: R 134
Ambient Temp: 65
Pressure Low: 70
Pressure High: 100
Country of Origin: United States

new to the site and looking for a guru

vehicle: 1969 Chevelle with factory air A6 compressor
refrigerant R 134

POA valve was adjusted to 26 PSI
( perform this adjustment on a bench by attaching shop air to the evap inlet side and increasing the pressure slowly and watching the low pressure gauge which was attached to the low side port) turn set screw CCW to set pressure
results: POA valve leak slightly below 26 PSI but there was a notable pop at 26 PSI and substantially more air passing through the valve.
The low pressure gauge reading would then increase as the shop air pressure was increased at the valve inlet. 30,40,50 PSI
POA valve is a not rebuildable aftermarket replacement type

System is currently under charge (36 oz)
static gauge pressures is 85 PSI high and Low

compressor starts clutch engages no abnormal nose
Ambient temp 68
Blower fan set to high

POA valve frosting mid way right after low side port along with suction line all the way back to compressor
Evap stays warm
Gauge pressures: low 75 high side 100

If i pinch liquid line (from condenser to expansion valve) close to expansion valve, creating a blockage ,
pressures are: low 20 high 105

expansion valve what just change

what is happening here?
Could this be a faulty POA or compressor?
should i keep changing?
what can i rule out?

any help would be greatly appreciated

mk378 on Wed September 26, 2012 9:46 PM User is offline

The POA is not opening fully. It should be wide open at 75 psi. In the bench test once the set pressure is exceeded it should be able to pass lots of air without the pressure increasing.

Edited: Wed September 26, 2012 at 9:47 PM by mk378

modicab on Thu September 27, 2012 1:40 PM User is offline

MK 378

So the bench test for the POA valve should be as follows
set up: Shop air at inlet, lower pressure port connected to manifold gauge.

results/procedure: slowly increase shop air to set pressure, hear a notable pop at set pressure (26 PSI in my case)
continue to increase shop air higher then set pressure (30,40,50 PSI) but the low side gauge stays at set pressure (26 PSI in my case)
Is this correct?

Thank you for your help


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