Air Conditioning on classic vehicles with R12


Classic vehicles with R12 A/C systems.


If you own a vehicle manufactured before the early 1990's you might already know all about R12 refrigerant gas. R12 was used in new cars until around 1992 - 1994 when the newer, more environmentally friendly replacement R134a was introduced. R12 was phased out on 01/01/1995 and banned outright on 01/01/2001. It is now illegal to use and unobtainable anyway. If your vehicle was built to use R12 this leaves you with the problem of what to do if the Air Conditioning is not working or needs to be regassed. Here are two alternatives available to you:

Option 1. The good news is that there are gasses which are a direct replacement for R12. The gas we use is commonly known as R437 or R437a (Isceon® MO49Plus™). This is the most up to date replacement for R12 (and supercedes RS24 / R426a). One of the main advantages is that it is a "drop in replacement" so there is no need to change the lubricant in the compressor or any of the components. We would however recommend you consider changing the drier especially if it is the original unit. The drier is designed to remove tiny amounts of moisture from the system and older models contained desiccant which can break down when saturated (or old) and clog up the valve and pipework. On a Jaguar XJS V12 for example these are usually around £30 to buy and very easy to change as they sit on top of the condenser right at the front of the engine bay.

The downside to using R437a is the price. As there is so little demand for the gas it is quite expensive compared to R134a and the cost for regassing a vehicle would be around £90 (500gms of gas) to £130 (900gms of gas) depending on the amount of gas required. This compares to £50 to regas any typical R134a car (500gms of gas).

Rolls Royce Silver Shadow
Rolls Royce Silver Shadow with R12 A/C

Option 2. Your vehicle can be converted to use R134a which was a relatively cheap gas (until recently) as it is widely used today. R134a is now being phased down so the price is shooting up - it has risen 600% in the last year. However R134a is not compatible with the mineral oil that was used in compressors with R12 so the compressor would need to be removed, the system flushed and the compressor filled with new oil and replaced. Additionally the drier would also need to be changed and on some vehicles the valve needs changing too. R134a has very small molecules and can often leak through the seals and hoses designed for R12 so it is also possible that you may need to change all the pipework and seals throughout the air conditioning system. Lastly R134a is not as good a refrigerant as R12 so you may find that the temperature from the air vents inside the vehicle does not get as cold as it used to either.

To summarise R437a is the best option in our opinion as it is a direct replacement and also provides up to 10% better cooling capacity vs R12. The only downside is the cost but that seems insignificant compared to the cost of the additional work needed to convert your classic car to use R134a.

There are many pre 1992 cars still being used today including Jaguars, Bentleys, Rolls Royces, Ferraris etc and we have recently worked on a Nissan Figaro for a lady locally who loves her little old car but could not get the air conditioning sorted out anywhere else.

Nissan Figaro

Please note: due to a lack of demand for R437a we now order it in when required rather than keeping it in stock. If your classic car has no gas in the air con system then it must have a leak which needs locating before refilling with gas. Lastly don't assume it just needs refilling with gas, we often see vehicles which have other issues such as electrical faults and are still filled with R12 gas. Please also bear in mind it may take two visits to sort out the problem with your air conditioning, one to establish the problem and another to fix it once the required parts or materials have been sourced.

We hope you haven't found this information too confusing with all the "R" numbers! If you have an older vehicle with air conditioning in need of some tlc please contact us now for a friendly, no obligation chat - we are car enthusiasts too!

We cover all areas within a 25 mile radius of Derby including Ashbourne, Burton on Trent, Castle Donington, Long Eaton and Uttoxeter.