AC questions

[69riviera]

hoping someone here can help diagnose an AC problem. with gages hooked up and about 75 outdoor temp i have 30psi suction and about 150 head pressures, but very little or no cooling. i have bubbles in sight glass, but when i try to add freon(r-12) the suction pressure won't rise at all and i don't get rid of the bubbles in the sight glass. i did notice frost build up on the small line from POA valve to evap box after 15-20 min of running. compressor sounds normal and clutch is pulled in. was thinking of replacing POA and Expansion valve, but not sure thats my problem. any ideas?

[Smartin]

Heater door not working properly?

[69riviera]

Heater door not working properly?

well maybe, but it doesn't seem to want to take enough freon to clear sight glass even tho there is plenty of pressure in the tank, so thought maybe the problem was freon related. i'll check the door to see if its closing tomorrow. thanks for the idea.

[69riviera]

so it must be a refrig problem any ideas as to cause? the large suction line to evap is warm, when i added r-12 the small bleed line from POA to Expansion valve frosted up, but all other lines were warm or hot. bubbles in sight glass remained and head pressure rose some with added r-12, but suction stays at 30#'s. seems its a metering or flow issue, just not sure how to tell if its POA or Expansion valve. any other thoughts

[Buick64203]

I would recommend changing the POA valve. From the frost on the line,I would say you have a clog in it. the POA valve is the predessor to the modern day orifice tube

If you have 30 psi on the low side, you should have 30 degrees coming out of the vents. Pressure equals temperature.

make sure before you charge the system, that you hold it under a vacuum for a 1/2 hour. It will boil off any moisture in the system. Plus under a vacuum, the freon will suck right in.

[69riviera]

i'm thinking maybe just change the POA and expansion valve and be done with it, maybe should do the drier as well? thanks guys for all your help, i sure appreciate it.

[69riviera]

ok, here's the outcome to my AC issues. i changed the expansion valve and drier with NAPA current replacements. i evac the system over night and measured in 4 lbs of r-12 using my digital bathroom scale. ambient air temp of approx 80 degrees, i had the following: vent discharge air temp of 41 degrees, suction pressure of 35 psi and discharge pressure of 195 psi. at this point the suction line had frost from the POA to compressor on suction line with sight glass clear, so i added another 1/2 lb of r-12 and the line thawed and is now just sweating. i think that is pretty good according to service manual, so looks like i'm good to go. there is a little "bounce" in the high side gage-kinda vibrates 2-3 psi-hope thats ok? thanks again for all your input guys!! Now if i want the OEM look i'll have to send out my old expansion valve and drier for restoration, but for now i am COOL!!

[Buick64203]

The Riviera AC system takes alot of Freon. Offhand I think its 4.75 lbs. Sounds good to me. Sweating is normal, frost is not

[69riviera]

The Riviera AC system takes alot of Freon. Offhand I think its 4.75 lbs. Sounds good to me. Sweating is normal, frost is not

my sticker says 4.25 lbs, but my muffler is missing so might be a bit less.