Converting to 134a - Ford

R-12 "Freon" and 134a

Until 1995, most cars with air conditioning used R-12 Freon refrigerant which has shown to have an environmental impact. R-12 is no longer used or produced in many countries and remaining quantities have skyrocketed in price. Since then, the industry standard has been R134a, which is an efficient replacement. Contrary to popular belief, most cars originally equipped with R-12 can be converted to 134a and still keep you just as cool.

Understanding the basic type of a/c systems Ford used on their classics will help with you determine the best route for your project.

Cycling systems

This is also a generic term for both early ford systems and later and modern systems where the clutch on the compressor engages off and on to regulate refrigerant. In these systems, when the air conditioner is turned on, the compressor clutch is engaged until certain pressures and/or temperatures are reached in the system. Once this criterion is met a pressure switch or thermostat opens the clutch power circuit and disengages the clutch, stopping the circulation of refrigerant.

Bypass systems

This is a generic term for the later (Early 70s), valve regulated systems for Ford vehicles. In these systems, when the air condition was turned on, the clutch on the compressor was engaged until the air was turned off. When the system reached certain pressures and/or temperatures a valve opened and allows the refrigerant to continue to circulate. This is much different than the original and then newer systems where the compressor clutch engages off and on to regulate refrigerant. This is where the old adage of turning off the air to save gas came from. Because no matter what the compressor was working all the time when turned on.

Ford Temperature controlled Systems

Nearly all early Ford air conditioning systems are cycling systems. They did not experimet with a suction valve (bypass system) until the early 70s and then abandoned it. What they use is a somewhat simple system where there is a thermostat that has a temperture probe in the either the fins of the evaporator or clamped to the suction tube of the evaportor. It senses the ideal temperature before the evaporator freezes and simply opens the clutch circuit and the clutch diengages until the temperature drops to a specified level.

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.
• Charge with 134a between 70-80% of the original R12 charge amount.
• Replace any o-rings with 134a compatible.

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.

Systems w/POA Valve
(aka Suction Throttling Valve & By-Pass Valve)

The POA Valve is installed on the evaporator, near the firewall.

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.
• Have POA Valve Rebuilt & Recalibrated.
• Charge with 134a between 70-80% of the original R12 charge amount.
• Replace any o-rings with 134a compatible.

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.

Systems w/Accumulator

The accumulator is most often installed on the evaporator, near the firewall, but occasionally found in the middle of the suction hose between the evaporator and the compressor.

Minimum Requirements

• Change or restore the accumulator.
• 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.
• Charge with 134a between 70-80% of the original R12 charge amount.
• Replace any o-rings with 134a compatible.

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.