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ac not blowing cold

blasterx2g on Fri April 18, 2008 12:45 PM User is offlineView users profile

Year: 1972
Make: chevy
Model: chevelle
Engine Size: 350
Refrigerant Type: r12
Ambient Temp: 85
Pressure Low: 40
Pressure High: 150
Country of Origin: United States

My chevelle got out of the paint shop after 6 months and the system was very low. Put in r12 and its not blowing cold anymore. pressure wont raise to over 150 on high side and it continusly cycles. Low side doesnt cool anything down as far as hoses/pipes. I have replaced the poa with a straight tube so shouldnt have any issues with that. COuld the expansion valve be blocked from sitting for that long? what else could it be? I also dont see bubbles going through the system even though its almost fully charged

mk378 on Fri April 18, 2008 1:22 PM User is offline

Why is it cycling? Compressor should be on steady with those pressures.

Whenever a system comes in "very low", find and repair the leak before putting more R-12 in. It could be leaking out almost as fast as you're putting it in.

bohica2xo on Fri April 18, 2008 1:24 PM User is offline

Paint shop? Check the condensor for a coat of paint. If the body shop had the system open, check for 134a contamination (or unauthorized conversion)

POA eliminated? Cooling eliminated with it. Return to stock components.

TXV clogged? A possibility for sure. Inspect & replace if blocked.

No bubbles in sight glass? Fully charged R12 system.

Cycling? OEM A6/POA/TXV system did not cycle. Repair as needed to return to OEM configuration.


"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

blasterx2g on Fri April 18, 2008 2:03 PM User is offlineView users profile

I repalced the original broken poa with old air products straight tube. I had no other choice due to not being able to find anothe rpoa. Its worked great for 7 yrs with the straight tube. Its made to cycle with the tube. I wouldnt put it past the paint shop to take my freon. It did have a very small leak before it went in. Leaks 12oz a yr but was very low and figured it was from sitting for 6 months. I will replace the expansion vaalve this week to see what it does

blasterx2g on Wed April 23, 2008 9:28 AM User is offlineView users profile

ok..Replaced the expansion valve and put 3.75 pounds of r12 in the system. works great until a few miles down the road and the bottom tube from the expansion valve freezes up. what next? Adjustment of the aftermarket POA tube?

mk378 on Wed April 23, 2008 10:08 AM User is offline

Having a real POA valve will prevent freeze-up. Trying to cycle on pressure instead is a poor substitute. If you insist on running without a POA valve I suggest doing what most TxV systems do, which is using an evaporator temperature switch to cut off the compressor before the evaporator can frost up.

blasterx2g on Wed April 23, 2008 10:24 AM User is offlineView users profile

i ran the poa tube for 7 yrs with no issues so wasnt sure why im having one now. Do the tubes eventually go bad? Where can i even get a regular POA without paying big bucks?

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