Air Conditioning Gas Quantities

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AC Gas Type And Quantity

February 2016 (ish)

This date is the best I could get from smart. Looking at the AC pipes on the parts system, the swap over date is Feb 2016.

However, you should check your car before ordering any gas. It doesn’t matter if you are taking it to a specialist since (apparently) the connectors are different between the 2. If you look carefully, at least 1 of the pipes at the front will state what gas it’s designed for.

Gas Type

Since the beginning of the smart, the air conditioning gas type used was R134a. The European Union decided that R134a was shit-in-a-can and it would single handedly destroy the world. So they chose a replacement, made by Honeywell and was called R1234yf. It had a far lower GWP (Global Warming Potential).

R134a has a GWP of 1430.
R1234yf has a GWP of 4.
Carbon Dioxide (CO2) has a GWP of 1.

In 2011, the EU made up new rules stating that all new car platforms must use R1234yf. The 451 had already been released so smart weren’t required to adapt it to use the new type of gas. However, Mercedes, Audi, VW and BMW refused to use R1234yf for 3 reasons.

It is less efficient.
The system has to be at a higher pressure.
R1234yf is flammable.

The new R1234yf systems have to be more robust due to the pressure, plus it has to not leak as easily in a crash.

So, for years, Daimler pushed back against the EU despite fines and legal threats.

Because of this, even when the 453 was released, it was still using R134a gas. Mercedes aren’t happy with having to use R1234yf and are looking at moving towards CO2.

Can I Put R143a In An R1234yf Car?

In most countries this isn’t legal but you can do it yourself or find a shady AC gas man. All AC gas refill companies will say you absolutely shouldn’t do this but it’s mainly because they want to sell you the more expensive R1234yf gas.

R1234yf systems run at a higher pressure because it’s less efficient compared to R134a systems. Running R134a gas in a R1234yf system could possibly over-cool and freeze up the condenser. If the cooling cuts in and out as it runs, try reducing the amount of gas in the system.

The refill points are a slightly different connection between R134a and R1234yf so you’d probably need an adapter for the refill can.

You MUST remove all of the old R1234yf gas and oil from the system as it doesn’t react well when mixed with R134a.

Ignore the gas fill capacity on the car’s label because the 2 gases have different weights. You will have to go by pressure. The R134a refill can will have a pressure gauge but the dodgy AC gas refill company should be able to calculate the correct fill amount. The oil quantity is the same between the 2 gas types.

Oil Type

To keep the compressor running smoothly and to keep the rubber O rings from drying out, a percentage of the air conditioning system is filled with a refrigerant oil. This oil is normally PAG 46 (Polyalkylene Glycol) but PAO 68 (Polyalphaolefin) is compatible.

PAG 46 is thin, PAG 100 is medium, PAG 150 is thick.

*However, oddly, on the 451 Electric Drive (ED), the car recommends PAG 1234. This oil is specially designed for AC systems running R1234yf gas but as you can also see, it runs R134a.