Automotive Air Conditioning Information Forum (Archives)

klopper92 on Mon August 18, 2014 9:38 PM

Year: 1967
Make: buick
Model: gs 340
Engine Size: 340
Refrigerant Type: r134
Ambient Temp: 87f
Pressure Low: 104
Pressure High: 130

hi im new here and i need some help! started out recalibrating the poa on this car and replacing all o rings.
filled with 3.6 lbs r134 and 8.5 oz esther oil. ran system and got 105 hi reading and 16 low. had higher than ambient temp into exp valve
inlet line. outlet was ambient. felt like exp was stuck closed so evacuated system and replaced expansion valve with new unit from
orileys. now with charge of 3.0 freon i have hi side of 130 and low of 104.
the suction hose from outlet of poa valve is frosty and checked at 40 degrees with infared therm.
seems that the poa is acting like a expansion valve since it has such hi psi entering it from the evaporator.
am i correct in thinking that the new expansion valve is hung open?
the kicker is when all these tests are ran the that i have expansion bulb submerged in ice water
versus ambiet temps the pressures never change on gauges.
sounds like stuck valve.
but whats odd is when car is turned off the pressures take a very long time to equelize between low and hi side.
any help and ideas is greatly appreaciated!
note that first fill with freon was with small cans and thats why i over charged it. the second fill up was at work with recovery machine
the spec on vehicle is 3.25 lbs and i used 3.0 as a start since i read that the 134 volume doesnt need to be as much as original r12 required


Edited: Mon August 18, 2014 at 9:41 PM by klopper92

mk378 on Mon August 18, 2014 9:54 PM

It would appear that the POA is stuck (almost) closed, allowing the evaporator pressure to rise until no cooling occurs. POA should be wide open at 104 psi. Instead it is just cracked open and acting as the expansion device.

klopper92 on Mon August 18, 2014 10:07 PM

thanks mk378 for the quick response! when i tested the poa i used 60 psi into the inlet of evap with the with the exp removed because original exp would not let 60 psi pass through it.
with low side gauge connected to poa valve at factory shrader it would maintain 34 psi when constant pressure applied and drop to 29 and hold there when i stopped pulling trigger
on blow nozzle. i recalibrated so it was set at 26 holding psi. i assumed that this meant the poa was functioning correctly.
is there another way to test it or verify that it is whats giving me fits?
i have another poa and evaporator and when i blew through it with 60 psi it made no pressure on my gauge and all the pressure applied came straight out the suction line side of it.
i guess its stuck fully open.

mk378 on Mon August 18, 2014 11:17 PM

In a bench test you should connect the POA inlet direct to the air line and turn up the applied pressure gradually using your air regulator. When the set pressure is reached it should open rapidly and let a large quantity of air through.

klopper92 on Tue August 19, 2014 7:17 AM

Going over this in my mind I also have noticed that when car is started and compressor is turned on
That it will pull low side down about 15 psi pretty quick for about five seconds and then shoots back up
To 100 ish and longer it runs will climb higher. I assume the later climb is due to heat soak from excessive pressure.
So it seems suction line pulles on poa and starts working and then it just cant meter enough volume to
Keep evap side psi down.so I agree with your idea of bad poa but I do want to test the exp valve
Off the car with heat and ice water too when I open system back up to verify it opens.and closes
Since it is a cheap parts store murry version. Poa was clean inside when I had it off first time. Is
There anyway to tell.what restriction is within it without sending to someone to rebuild it?

klopper92 on Sun August 24, 2014 6:03 PM

Want to say thanks mk378. I piddled on car yesterday and started car with expansion bulb in a block of
Ice I drilled a 3/8 hole in and and low side psi was still high. 90ish. Started gently tapping
Poa valve with ball peen hammer. After about a dozen taps the low side reading dropped to about
20psi and inlet line to evap got frosty cold ! Thanks for the advice

mk378 on Sun August 24, 2014 6:30 PM

Next put the TXV bulb back on the evaporator outlet line where it belongs with some insulating tape and see what you have.

klopper92 on Sun August 24, 2014 7:14 PM

I put it on the evap outlet line as far down as I could without removing inner fender to install
Properly cause we had a show to attend last night. Zip tied it and put doughy goop around it for a
Temporary rig until I have time to take all the way apart. It actually cooled pretty good on the drive to and.from
Show and.it was 92 degrees outside! What is the proper putty I need to get to install the.bulb when I do pull it apart ?