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134a charging problems

oledave60 on Mon November 09, 2009 10:33 AM User is offline

Year: 1973
Make: Chevrolet
Model: Camaro
Engine Size: 350
Refrigerant Type: 134a
Ambient Temp: 72
Pressure Low: 80
Pressure High: 110
Country of Origin: United States

I am converting to 134a. New(rebuilt) compressor, new condenser, dryer, expansion valve and hi/lo switch. New green o'rings. Pulled 29 in vacuum for 1 hr. Held vacuum over night. Added 24oz of 134a, suction line and 2/3rds of poa valve have ice, tube coming from evaperator is warm. Will not take anymore refg.Is this a bad, clogged or stuck POA valve or something else? Thanks for any and all help.

Dougflas on Tue November 10, 2009 1:12 AM User is offline

Did you recalibrate your POA for 134 refrigerant? Did the system work before you attempted to convert? If not, did you test the POA? POA's can show some frosting when not completely charged. 72º is not really a good temp to charge as you're at the min point of performance. I like to see in the 80's or higher. To test the POA on the vehicle, unplug the blower motor. The low side should be 28 to 32 psi for r12 and about 26 for r134 after the POA is calibrated. Another problem point on these systems was the oil bleed line plugged up from oil.

mk378 on Tue November 10, 2009 9:17 AM User is offline

Recalibrated or not, the POA valve should be wide open at 80 psi. It does seem that the POA is not working properly, it is working like an expansion valve. You should be able to get the low side to drop by disabling the evaporator fan. If it does not, the TXV would likely be bad.

oledave60 on Tue November 10, 2009 2:34 PM User is offline

Thanks for the replys. The system did not work before all this and it had been open for sometime. But all the old componets were flushed good and dried with dry air. I calibrated the POA per instructions posted on this forum by Mitch on 7-24-03. His post was detailed and had how to picture. When I blow 60lbs air through expansion valve (which is new and for134a) I have steady flow of 26lbs out the POA. I have tried to charge twice, both times same result. It will take 2 cans (24oz) then both metal ends of suction line freeze up as well as POA fromcharging port to suction line. The evaporator feels warm. I tried a third can for over 30 minutes and it didn't seem to take any of it and the pressures didn't move. I will try wihout blower and let you know. Thanks again

oledave60 on Tue November 10, 2009 3:46 PM User is offline

Disconected blower and got about 1/2 of third can in . Low side went from 70 to 85 and high side went from 110 to 125. Still no cooling in evaperator, but the inlet tube is slightly cool Temp today is 75. Outlet 2/3 of POA still turns to ice

Dougflas on Wed November 11, 2009 5:33 AM User is offline

^There is a schrader in the POA. By any chance did you remove it? It is NOT a standard schrader but a special one.

oledave60 on Wed November 11, 2009 10:14 AM User is offline

The schrader valve is still in the R12 port with the 134a adapter screwed on top of it. The 134a adapter has some type of valve in it, but it won't hold pressure in either direction.

Dougflas on Wed November 11, 2009 12:43 PM User is offline

Not the schrader I'm speaking about. ON the POA, there is an oil bleed line/fitting. There is a special schrader in this port. Is it still there and did you remove it? If you put any old schrader back in, the POA will not work.

oledave60 on Wed November 11, 2009 12:59 PM User is offline

That' the schrader in the oil return port, right. No I didn't remove it or mess with it at all. Should this be tested and if so how. Thanks

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