Recently the owner of a ’65 Mustang asked us how to convert his car’s original compressor to use R134a refrigerant (also known as 134a). Production of R12 Freon was discontinued in 1995 due to concerns about R12’s damaging effects on the ozone layer. The more environmentally friendly R134a has been used in most models since then. Assuming the compressor is in good shape, the owner of this 1965 Mustang can convert from R12 to R134a. Here are the steps to take to make sure the converted AC system gets nice and cold.
1. Drain the compressor oil and recharge with a full charge of R134a compatible oil such as PAG or Ester Oil. Flush/clean any existing parts such as the evaporator to remove all traces of the old R12. Depending on the condition of the component and the level of contamination, this may be a simple matter of blowing it out with compressed air, or liquid flushing with a good-quality AC flushing agent (available at local parts houses).
2. Replace the old R12 serpentine condenser with a more efficient one. We offer a mechanically correct version of the 64-66 Mustang condenser that is a direct bolt-in replacement. Our version is a 6-circuit serpentine pattern designed to handle the higher pressures and heat loads generated by the R134a without any loss of efficiency.
3. We recommend replacing all hoses when making the conversion to 134a, but if the stock liquid and suction hoses are in good condition (not kinked or scuffed too badly, with clean flare-seats), it’s possible to make the conversion by replacing only the discharge hose. This is the hose that connects the discharge side of the compressor to the top fitting on the condenser. It is made of rubber, while the rest of the hoses in the system are made of nylon.The old rubber hoses have no barrier to prevent the R134a from passing directly through the old hose. We have the correct discharge hose in reproduction.
4. Replace or restore the filter drier. Not only is this the filter for the system, it also removes moisture from within the system. This part is designed as a throwaway part that is good for one use. It should be changed not only when converting to 134a, but each time the air-conditioning system is opened to the atmosphere. If the filter-drier is not changed, significant problems can arise from contamination to a clogged filter screen within the filter-drier, or a build-up of acids resulting from the combination of moisture mixed with refrigerant and lubricant that will corrode the system from the inside out.
5. Install R134a charge port adapters.
6. Charge with R134a to between 70-80% of the original factory R12 charge amount. On a 64-66 Mustang this comes out to 20 oz. R134a.
Note: Ignore the sight glass. It’s not unusual for a properly charged R134a system to show bubbles in the sight glass.
Breakdown of Parts Needed
11-101 64-66 Mustang condenser
12-101 64-66 Mustang filter drier
05-127 134a oil — 11 oz. bottle
13-118 64-66 Mustang discharge hose V8
14-122 Ford 134a adapter set straight
More information about parts and services for your Mustang can be found in our Mustang catalog and price sheet. On our website we also have a list of steps for converting Ford R12 AC systems to 134a, as well as a diagram of Ford service valve positions.
If you have more questions about converting your classic ride to R134a, send us an e-mail or give us a call and we’ll be glad to help.
Converting Other Model AC Systems to R134a