has anybody out there just changed freon without changing poa valves?ive talked to a bunch of people and have gotten a different answer from everybody.some say adjust the expansion vavle.some say dont touch the expansion valve just get a poa vavle for 134a,other people say just ,flush,oil vac and put in the 134a,"it will work fine".so far i have changed the o-rings to the blue/green ones.i am at a crossroads and dont know where to go next!!! o No:
I changed mine and only changed the receiver dryer tank which you should always do upon this change. I then just had a shop change the oil and charge it up and it works fine. Don't bother with the POA valve. My system has worked fine for two years now. You should also use less charge of 134. Use about 3 lbs. That spec for R12 was 3.75 lbs. on a GS or skylark. I also unscrew the larger valves and keep them in the glovebox and put the old ones back on so they look stock. If it needs a charge I'll just screw the others on. I also did not put a 134 sticker on.
I do the conversion on all the cars I build. My friend is a local AC man and he adjusts the POA valve. If not, you will not get maximum cooling at idle....probably not a big deal where you are ...NY.... but in FL....must have item. I have done several previous conversion w/o the POA adjustment and it does not work/cool well at idle/low speeds. So, I have empirical evidence supporting my friend and it does not take him much time to adjust the POA valve. He does this all the time. Up you what you want to do.
George is correct about the POA valve. It must be adjusted to work as good as the R12 due to the pressure differences. It is a easy thing to do on most gm cars. Look in the end of the inlet side of the POA valve and you will see a adjustment set screw and lock Nut. take the set screw and turn it counterclockwise a 1/4 turn and tighten the lock nut. In most cases this is all that will be needed . This is the instructions recommdended by the Gm for any expansion valve R12 system. Of coarse if you are not worried about the stock look you can eliminate the POA valve all together and use a new pressure cycling switch. It replaces the valve and cycles the compressor like the newer vehicles.
You might want to consider one of these. http://aircondition.com/vov/ I use one on my Regal GN 134 conversion. Works great! :TU: ElectraJim
The New green o-ring gaskets are recommended but not required. But for the average 7-10 dollars it cost for a kit it is really a no brainer. Plus the material used to make the new o-rings are a much better composite. Usually most 30 year old cars have the stock O-rings in them somewhere, so it is best to replace them. Most auto parts stores have them in kits and go figure they are usually green or blue. My advice would be to replace them.
Did that adjustment about 2 years ago on my 71 Riv when I converted it over to 134. Made a huge difference at idle and even at higher rpm's it was cooler. It brought the pressures in line with the 134 refrigerant and worked well. I would do it again if I had another older car.
12 to 134a Shop manual says the POA is not adjustable on '72 fullsize. What to do? I plan on just taking the car to a shop to have the system converted. Should I purchase any of the parts beforehand, or just let them do it. I can get a receiver/dryer ordered but it takesanywhere from 1 to 5 days. Thanks. Mitch
Try looking thru this site for info. Somewhere in here is where I found the info for the adjustments for the poa and expansion valves. Sorry I cannot find the original post there. But this seems close. http://www.autoacforum.com/messageview.cfm?catid=20&threadid=7567
Thu July 24, 2003 11:18 PM Here is a pic of the test setup for on the car testing of the POA. Pretend the evap coil is in the box on the firewall. Hook up a low side gage to the POA port. Blow 60 psi air into the TXV using a rubber tipped gun. Read the gage and adjust the POA pressure with the socket in the outlet to 29 psi for R12, or 26 psi for 134a. Check to make sure the valve setting is repeatable.
Mitch, The POA valve you have pictured is adjustable. Once you take it apart see if there is a nut for adjustment. If not, you can send it to my friend and he can do it for you. Ones w/o the nut require machine work (lathe). He then re-welds them and they work great. Contact Tim. His site is www.thepartguy.com
