I have just finished restoring a nice 67 Eldorado Cadillac. Its charged wiht R12 has a newly rebuild compressor, new expansion valve, new dryer and all flushed out. Great vacuum and mostly all new parts.
I am not happy with the AC yet thought. Its 100F outside today measured near the front of the car. I hooked up the gauges and get 40 psi for the low side and 280 for the high side. The temp inside the vent with the AC on high is 57 after about 10 mins. The motor is running at 1580 RPM in neutral with the fast idle vacuum idle kicked in. If I cruise down the road at 60 or so I can see the vent temp go down to 45 ish. The vent temp will get down to 49 or so and the low side pressure drop if I run it at 1600 RPM for about 20 mins.
I am running with R2, really good Fan and fan clutch so the radiator runs cool even on a very hot day.
The problem is that the vent temps go up to about 60 just sitting and idiling in gear. Can I do better somehow? The car used to have a POA which seemed to work but when I was rebuilding everything I switched it out for a pressure swich replacement. I have read on this forum how the old POAs can be adjusted should I put that back and start over?
1) The 45f vents at highway speed vs 60f vents idling just scream "Condensor airflow issues". Non-OEM fan or fan clutch, missing fan shroud, missing seals allowing air to bypass the condensor... Just because the engine does not overheat you can't say the condensor airflow is adequate.
2) Your pressures also indicate poor condensor airflow (2.8x ambient high side), and the low side should be much lower, and stable.
3) The missing POA valve. When I finally got to that point, some of the previous things began to make sense. Your pressures are all over the place, partially because of the cycling clutch system you installed. What is the cycling switch set at? You really should re-install the POA if you want OEM performance.
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.
I have not looked into the condensor area yet. I am going to take off the blower motor and look in there to see what is what. I should have taken that all out when I restored the car. It looked good from the outside so I was a little afraid to take it all apart since parts are impossible to get. I always fear breaking rare parts.
This may be a big part of the problem though since even on high the air force comming out of the vents just does not seem strong enough. I know the fan is blowing full speed because I have checked the voltage in high. The clutch and fan are new and pulling lots of air.
I will put the POA back on when I inspect the condensor. I was a dummy for taking it off but some adds convinced me that modern technology was going to be better. Ha! I am glad I kept the old valve.
I am not sure but I think the pressure switch goes of at 20lbs or less.
Do you have a full charge in the system? Your vehicle calls for a full 4 lbs of R-12 - 64 oz - do I love those old cars! My 05 DTS only uses 36 oz of R-134a.
By all means put that POA valve back in. Anyone that tells you to remove a POA and install a device to make the compressor clack on and off doesn't have a clue.
Do you clamp off the heater hoses for 15 minutes and recheck vent temps? If vent temps improve, you could have some heater action diluting the cool air. You really should have ice cold vent temps with 40 PSI low side readings. The high side readings are within spec at 100F.
I agree with Bohica, with a cutout of 20 PSI that evaporator should turn into a block of ice with the A6 pumping R-12 through it.
Hey about a little treat for us here... post some pics of the restoration!
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