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a/c pressure diagnosis

kato on Sat October 25, 2014 9:43 PM User is offline

Year: 1995
Make: Mazda
Model: 626
Engine Size: 2.0
Refrigerant Type: 134a
Ambient Temp: 83
Pressure Low: 55
Pressure High: 25
Country of Origin: United States

Hi, new to this forum. Originally, my 626 a/c blew warm air. Low side about 25 psi. Didn't hook up high side manifold gauge yet. Gave a 12 oz charge. No change. Tried another can and half way, no change, I hook up high side and it ran at about 340 or so. Suspecting it was a clogged expansion valve, I replaced it, replaced all of the o-rings in the lines, evacuated for about 1/2 hour and recharged with a 12 oz can. It now reads low @ 50 and high @ 25lbs. Did I mess up on the expansion valve install? Is it stuck wide open? I was careful to bend the small copper tubing into place but I may have kinked it. I rewrapped the bulb with the original wrap. Any help appreciated!

Dougflas on Sun October 26, 2014 12:20 AM User is offline

You can not just add refrigerant while monitoring just the low side. You had 340 high side and that indicates a possible over charge. You probably wrecked your new expansion vale if you kinked the copper line with the sensing bulb on it. You can check TXV operation by removing the bulb from the line, placing it in your hand for a minute or two while looking at your gauges. Then place the bulb in ice water and look for pressure changes. If the line is kinked, the valve will not have P1 pressure to open the valve so that may be a possilbility that you damaged the TXV.

mk378 on Sun October 26, 2014 3:03 PM User is offline

Charge the proper amount by weight. You won't get any cooling from one can. 25 on the low side and something less than 340 on the high side is normal, the evaporator should be getting cold (maybe the heater is reheating the air?) Blockage in the TXV usually causes the low side to go below zero psi.

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