My 63 CDV factory A/C was trash so I replaced every part in the system and converted to R134 . I also installed a STV bypass kit which eliminated the STV all together and converted the system to a cycling system.  I vacumed and charged the system with 36oz of 134. The system is cycling as it should and the pressures are right at 250 high side, cycle off at 25lbs and cycle back on at about 35lbs. It is making plenty of water on the low side hoses and evaporator drain. There is very good air flow through the dash vents .

My problem is this, the best I can do on the vent temps is about 50-55 degrees on a 90 degree day, sitting in the garage or going 65 mph. At that temp I am barely able to keep from sweating. I have checked and double checked the outside air intake and it shows to be operating as it should , shutting off outside air while on recirculate. The techs (where I bought my parts} are great but they were unable to lend any ideas that I had not tried.

I am wondering if anyone has had a similar problem. 

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Comment by Mark S Anderson on July 23, 2018 at 10:46pm

Oil flooding is very common.  if it's filled with oil so much that it makes a problem, you should be getting higher pressures, though.   it would likely never cut off at 25psi.  If it's cycling off and not reaching temp, with the high side never going above 300, i'm still behind my opinion that it's obstructed. The pressure shouldn't go down with the temp staying up, unless the flow isn't adequate.  But still you need to rule out a duct problem, by measuring superheat coming out of the evap.  If the temp is correct there, and not at the vents, it's the mix door. or something like that.

Comment by Tony and Ginny 429 on July 23, 2018 at 10:19pm
Do we have an --Ac temperature pressure chart --for R-12 available someplace ?

Comment by Dana G Cooper on July 23, 2018 at 9:53pm

I had tried 36 & 48 oz today with about the same results. I talked with an old mechanic friend of mine tonight who suggested the system may be flooded with oil. When I replaced the evap, I installed the remaining needed oil into the evap before I installed it. 

Comment by Tony and Ginny 429 on July 23, 2018 at 8:46pm
If you installed 36 ozs and it SB 48 oz that should be your answer
Put more 134a into the system i would think

Are you working with the chart that tells you what the AC meter readings SB at a given outside temp ?

Comment by Tony and Ginny 429 on July 23, 2018 at 8:46pm
If you installed 36 ozs and it SB 48 oz that should be your answer
Put more 134a into the system i would think

Are you working with the chart that tells you what the AC meter readings SB at a given outside temp ?

Comment by Mark S Anderson on July 23, 2018 at 7:34pm

i may be wrong about the 4 lbs figure, that's for a 64-67 system, and it should be the same, but i don't have a 63 and it didn't occur to me that it might be different from what i'm used to, sorry if i'm in error about that.

Comment by Mark S Anderson on July 23, 2018 at 7:26pm

where did the 36 oz volume come from?  Manual says 4 pounds of r12, so you want about 75% of that amount in r134a.  Something more like 48 oz.  

Unplug the low pressure switch and run the system, see what the gauges are really saying.  If it's going to 25psi with vent temps in the fifties, then it's either low on gas or something is plugged up, since the evaporator is new and clean.  If the suction pressure goes to zero or a vacuum, something is plugged internally.   If it goes lower than 25 but stops above 5 psi, then you need to measure the temp at the evaporator return pipe (just before the stv) and see how much superheat you're getting.  If you're using a stock expansion valve, should be less than ten degrees.   I have a feeling it will be something more like 30, indicating a possible low charge.  


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