Not one, but CO2

NZ VASA director‘s workshop could be first outside the European Mercedes-Benz dealership network to repair rR44 AC systems

Unintended consequences. When Mercedes-Benz became the world’s first car manufacturer to factory-fit an R744 (carbon dioxide) air-conditioning system to the facelifted W222 S-Class limousine in 2017, the plan was to only release models with this groundbreaking HVAC setup in the European market.

Off-the-record sources suggest this was to keep a tight rein on vehicles featuring an as-yet unproven technology.

It’s also understood there were doubts over the ability of an automotive R744 system to perform satisfactorily in high ambient conditions, another reason why models running this refrigerant were restricted to European sale.

But official restrictions on where a model is sold when new have no bearing on where it ultimately ends up, which is why CoolCar Hamilton, operated by VASA NZ Director Catherine Tocker, ended up with two R744 models in the workshop at once.

It’s thought that CoolCar is the first non-dealership workshop outside Europe to attempt repairs on faulty R744 systems.

Gulf states grappling with R744

A number of online Mercedes-Benz forums have questions from a workshop in Qatar, dating back to 2018, whose customer had a C217 S-Class Coupe with  R744 system that was underperforming in the hot Middle Eastern climate.

“I’m working on a car, C217 2018 model S-Class coupe 400 4matic which was imported from a European Country (according to Star Diagnosis) which is equipped with a new generation gas R744 (CO2),” reads the forum post.

“The car was imported to a Middle-Eastern country (Qatar). And the customer has [a] complaint [that] the A/C is not cooling as it should.”

The forum poster asks whether it is possible to retrofit the system with R134a, the only refrigerant used by Mercedes-Benz dealerships in Qatar.

It is unknown what happened, although among the advice given by other forum members was that the customer should return the car to the seller and ensure its replacement has the ‘Gulf State’ HVAC and engine thermal management specification.

More recently, the owner of a 2018 S560 based in the United Arab Emirates posted on several Mercedes forums asking about repairing their R744 system after it suffered compressor failure.

Anyway, back to New Zealand, where the climate is arguably more R744-friendly than Qatar or the UAE.

How R744 cars ended up in NZ

If you were lucky enough to purchase a new W222 or C217 in New Zealand, it would not have R744 in its air-con.

But NZ is a parallel import nirvana, meaning at least two (a third is known of) right-hand drive examples have carbon dioxide coursing through their HVAC systems.

Or at least, did. One of them (the black one in the images) has a leaking compressor that is being replaced under Mercedes-Benz international warranty and the other had its warranty claim rejected, with two leaks in the system thought to be caused by accident damage.

Now diagnosed by CoolCar, both six-cylinder diesel S350d models are back at the local Mercedes-Benz dealership waiting for parts to arrive from Europe.

Once the compressor is fitted to the black car, it will return to CoolCar for a charge of R744 and re-testing.

The grey car is awaiting a pipe, which is yet to be ordered as the owner is wrangling over who is paying for the replacement. Once the grey car’s system is repaired, CoolCar will give it a charge of R744 and check it is working.

CoolCar identified two leaks on the grey car; bolts on the alloy block the right of the grey car’s high side service coupler were only finger tight and the washer was torn up inside, while a weld was leaking below the low side service port.

In New Zealand it is only possible to obtain refrigerant grade CO2 in huge cylinders, so CoolCar had to vent some of the gas in order to make the cylinder a manageable weight for scales with 10g increments.

The cylinder was so unwieldy that CoolCar Hamilton director Rodney Smith had to use a gantry to hold it upright on the scales.

Once running with a 410g charge of R744, system pressures are 1100psi on the high side and 500psi on the suction side.

CoolCar Hamilton acquired the equipment necessary to work on the R744 vehicles from Europe. Workshop owner and VASA NZ director Catherine Tocker said it was “quite an investment to gear up but worth it to be at the leading edge”.

Catherine said Mercedes thought low refrigerant in the cars was because they were de-gassed on export due to refrigerant flammability concerns (ironically), however leaks were responsible.

“The owners of these cars are pretty upset that they had no aircon all summer in their high-price imports,” she added.

Keep an eye out for updates on these R744 repairs in future editions of SightGlass News.