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A/C LINES ARE FREEZING UP

bigcoaxum on Tue May 13, 2008 10:42 AM User is offline

Year: 1973
Make: CHEVROLET
Model: IMPALA
Engine Size: 350
Refrigerant Type: R134A

MY A/C LINES ARE FREEZING UP. THE LINE THAT CONNECTS TO THE BACK OF THE COMPRESSOR AND THE LINE THAT GOES INTO THE EVAPORATOR CORE ABOVE THE EXPANSION VALVE IS FREEZING. WHAT IS CAUSING THIS TO HAPPEN? WHAT SHOULD BE MY FIRST STEP IN TRYING TO RESOLVE THIS ISSUE. SEEMS LIKE SOMETHING IS STOPPING THE FLOW OF MY FREON. I'M USING R134A RIGHT NOW BUT I WOULD LIKE TO SWITCH BACK TO R12. I HAVE NOT REPLACED THE EXPANSION VALVE OR THE DRIER CAN BUT I HAVE BOTH ITEMS HERE WITH ME.

ALSO, I'M HAVING PROBLEMS WITH MY A/C CYCLYING SWITCH. MY COMPRESSOR IS NOT KICKING ON AND OFF LIKE IT SHOULD. WELL ACTUALLY I'M NOT SURE IF ITS SUPPOSE TO KICK ON AND OFF OR NOT BUT I KNOW MOST OLD CARS SUCH AS THIS ONE DO. CAN ANYONE HELP ME FIGURE THIS OUT.

oznznut on Tue May 13, 2008 10:55 AM User is offline

Big
Did you resolve your air flow isues? Since you refer to a txv, I assume that your system uses a poa valve, is this right? A freezing line downstream of the poa with low heat load is normal. However, freezing out of the txv is not. What is the evap suction pressure measured at the poa. If you have not adjusted the poa for 134, it should read 30 psig. If it is way low, you have a clogged txv strainer.
Dave

oznznut on Tue May 13, 2008 11:00 AM User is offline

Big
Part 2. Unless you have one of those dreaded "poa update " kits, I don't believe you have a cycling switch. The A6 compressor runs all the time. The poa controls evap pressure, the txv keeps the evap supplied with gas.
Dave

bigcoaxum on Tue May 13, 2008 2:25 PM User is offline

yes, i resolved the air flow issue. my ducts were all screwed up and i replaced everything. thanks for your feed back. I "THINK" my system uses a POA valve. I'm not 100% sure though. I haven't tested the pressue yet, i'm just trying to save myself some money by doing it myself. I'll test the pressuer in my lines and let you know what i come up with. is it a good idea to replace the expansion valve and drier/receiver since the system is so old?

mk378 on Tue May 13, 2008 3:35 PM User is offline

If you have a POA valve it is a cylindrical thing in the line from the evaporator to the compressor. It will have a pressure testing port on it.

Many old receiver-driers are not compatible with R-134a, the R-134a dissolves parts inside. Debris will come out and foul up the whole system. If you had one of those you would probably know by now. Very good idea to replace it anyway. Expansion valves don't require routine replacement unless they get dirty.

oznznut on Tue May 13, 2008 3:39 PM User is offline

Big
It sounds like your txv strainer is clogged. Irrespective of load, the poa maintains the evap at 30 psig. This prevents the evap from freezing. That is of course, assuming that refrigerant is getting to the evap. Clogged strainer--ergo txv freeze up. Put in a NEW txv, NEW drier, use the correct charge of refrigerant and right type of oil. My 71 book lists 3 3/4 lbs of R12 60 ounces. Your 73 probably is the same.

Do a search for "POA" in the archives. Lots of good info.

Dave

bigcoaxum on Tue May 13, 2008 4:16 PM User is offline

do you recommend a certain type or certain "Brand" of R12 to use?? is it all the same regardless of the brand??

oznznut on Tue May 13, 2008 5:04 PM User is offline

Big
All the same stuff-just be sure is pure/virgin. Not recycled. If its recycled, must say so on can--- I think!!! No sealers, o ring conditioners, or other snake oil stuff.
Dave

oznznut on Tue May 13, 2008 6:15 PM User is offline

Big
Do a search in the archives author name impaladan73, date july 23, 2003. He did a repair/conversion of a 1973 Impala. Lots of detail, pictures, etc. Good read.

Dave

bigcoaxum on Wed May 14, 2008 8:28 AM User is offline

i did a search but only the username comes up for impaladan73. No info at all. how do i perform the search to get the info?

oznznut on Wed May 14, 2008 9:00 AM User is offline

Big
At the top of the first page of the forum, in the yellow area, click "advanced". In authors name type "impaladan73" . In the date boxes use 07/20/2003 and 07/30/2003. Click "search" . When the next page comes up, click on the item.. " 73 impala repair,"etc. Opens right up.
Dave

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