Hi everyone I'm going through the A/C system in my Riv (has never worked in the 13 years I've owned it). I was bench testing and trying to set the POA Valve for R134a by blowing ~100psi shop air through the evaporator. Instead of smoothly regulating to the 30PSI expected, the valve opens and closes repeatedly and the low side pressure fluctuates between about 25 and 27PSI. There is a loud honking sound that accompanies the valve opening and closing. I took a video of this happening. You can watch it here: Is this OK?
It probably would not do that with liquid refrigerant. Looks like its regulating as it should for 12. Im no expert on automotive systems.
Hey Briz Yeah I have no idea if this is normal or not. I’ve tuned it down a couple of psi to get in the ballpark for r134a. I was expecting it to be smoother in operation rather than regulating by opening and closing. If it’s even 1/4 as loud in operation on the car it will be unliveable. AC shops here would have never seen this kind of system before. Getting the system vacuumed and filled here is very expensive to just attempt and see how it goes.
Thanks for the suggestions. An update for posterity: The valve had initially tested OK when I first pulled the evaporator out. It started honking after I cleaned the mineral oil out with A/C Flush solvent. I added a couple of drops of PAG 150 oil to the inlet of the valve and re-tested. The valve stopped opening and closing and regulated properly at my new set pressure of 25psi and was quiet. It started to get a little bit noisy after some of the oil had blown out. With the system in proper operation there should be adequate lubricant flow. Whatever mechanism that is in the valve must require adequate lubrication to function correctly. Hopefully it has a few more seasons left in it. The valve had been open to the elements for approx. 2 years after I (foolishly) gutted all the old AC lines out of the car and didnt tape off the POA valve and TXV openings.
