The Eldorado leaked all of its refrigerant charge over the winter, so it was time to bring it back to the shop. It was recharged with R134 and all the necessary changes were made for the conversion.
I got a new remanufactured POA valve (suction throttling valve) from Classic Auto Air to make sure that the system can cope with the much higher pressures of R134. Classic Auto Air was very helpful with providing the factory correct parts. Classic Auto Air says that the re-calibrated valve can make a 15-20º F / 6º C difference.
Yesterday I got the Eldo back from the shop and so far it seems to cool the car down properly. The air discharged out of the vents is 10º C / 50º F cold - not bad for R134.

This is what Classic Auto Air is recommending for a change from R12 to R134:

Minimum Requirements

• Change or restore the filter-drier.
• Drain the compressor oil and recharge with 134a compatible oil. (PAG or Ester Oil)
• Insure that the system is clean and free of contaminants (Depending on component condition, this may be a simple matter of blowing out with compressed air or liquid flushing with an air-conditioning flushing agent)
• Replace or restore all rubber hoses with barrier hose.
• Install 134a charge port adapters
• Send POA valve in to be calibrated
• Charge with 134a between 70-80% of the original R12 charge amount.
• Replace any o-rings with 134a compatible

Recommended:

• Install hi/lo pressure switch

HELPFUL HINTS

• Ignore the sight-glass. A properly charged 134a system will likely show bubbles in the sight-glass.
• Typical 134a charge rate will be approximately 70-80% of the factory R12 charge amount.

The new factory correct POA valve. Internally it was calibrated for the use of R134 instead of R12. The expansion valve was also replaced together with the evaporator, condenser, compressor, O-rings, filter-dryer. I did not install a hi/lo pressure switch which would cycle the compressor on and off to keep the car original.

Tags:1967, Eldorado, 1967 Cadillac Eldorado Repair Tip, 1967 Cadillac Repair Tip, Aircondition, Restoration, POA Valve, R134, AC, ACC, Recalibrate, suction throttling valve