Just got my 72 A/C back together. I have a issue that I have never seen before. Been working on Auto a/c systems for years and have never seen anything like this. Lets start with whats new:

New A-6 compressor (not rebuilt)
New suc/discharge hose assembly (Ecklers)
New liqiud line (Ecklers)
new TXV (Ecklers)
POA conversion kit (Ecklers)
New reciever drier (Ecklers)

Basicly the only thing I did not replace are the condenser and evap.

Condenser and Evap were flushed with a/c flush solvent. Both seems to have good flow and no restriction. I know it is hard to tell with the evap being as it is plate and fin, however the condenser is tube and fin and flushing is straight forward. Now to whats happening:

Pulled and held 29 in of vacumn overnight. With 32 oz of refrigerant, presures are: low side 60-70 and high side 100-150. Ambient temp about 95. Discharge line is hot all the way to the condenser and about halfway through the top row. Drier sight glass shows flow but hard to tell how much. Drier inlet and outlet cool to touch as well as liquid line to TXV valve. Evap inlet warm. No refrigerant flow. It is very obvious that there is a restriction in the discharge side, but where?? As I said, the condenser seemed wide open when flushed. I know the problem could be in the new hose assem.(discharge), however brand new and unlikly (but possible). If it was a used or rebuilt compressor I would suspect could be the issue, but it is a brand new A-6.

Any ideas?? Thank you for your help.

 

did you change the filter? mine was slugged up pretty bad...also. you may have to much oil in the system... i did that also, and it also acted like a plugged system.

 

What refrigerant are you using?

 

Yes, new reciever drier. Using R134A. I usually charge to about 80-90% of r12 charge spec. System completely flushed. Only oil in system is what came in compressor.

 

the drier and filter are 2 different things in two different places.

im still running R-12, did you do an orfice change for the new R134a?

 

I don't know which one these systems use but is the orfice tube/ expansion valve functioning properly? If it is an orfice tube was it put in orientated correctly? Ie not upside down.

 

Dammest thing. Went down to my shop this am and was ready to recover the refrigerant. Said to myself, lets try it one more time...Works perfectly. Go fiqure...

1972 does not use an orfice tube. They use a Expansion valve. Also, the reciever drier is the filter as well as the dissicant to keep the system dry.

Anyway, thanks for the suggestions. All I can fiqure is on the intial startup, the condenser got the load of oil from the compressor and became slugged. After letting it sit overnight and with the pressures equalizing, it straighten itself out. As they say, never look a gift horse in the mouth!!

 

According to the CSM, pressure should be 29.5-30.5 psi on the low side of the compressor or at POA valve, @ 2000 rpm and 90* ambient air temp. with temp at right side outlet between 49-53* on MAX AC.

 

Thats just about where the pressures are running with mid 40's duct temps on high blower.

With the POA conversion kit, it changes form a gas bypass system to a low pressure cycling system. System cycles off at about 22psi low side and back on at about 38-40 psi low. Head pressures run about 250-275 psi at high idle (2000 rpm)

 

(literally).