The EU said Thursday it was taking court action against Germany for failing to force luxury automaker Daimler to use a new air-conditioning coolant deemed less likely to cause climate change.

Temperatures have reached boiling point over the long-running coolant row that has seen Daimler, the Mercedes-Benz builder, claim the new refrigerant makes cars more likely to explode in a crash.

Germany, Europe's top in car manufacturing, could face heavy fines if it is found to have infringed European Union laws.

The decision adds to the pressure on a German auto industry that is already feeling the heat from a separate pollution cheating scandal that has engulfed carmaker Volkswagen.

The European Commission, the powerful executive arm of the 28-nation EU, said in a statement that it had decided to refer Germany to the bloc's top court over the Daimler issue.

"The Commission alleges that Germany has infringed EU law by allowing the car manufacturer Daimler AG to place automobile vehicles on the EU market that were not in conformity with the (mobile air conditioning) directive, and failing to take remedial action," it said.

The EU warned Germany in September 2014 that it could end up in court if it did not act.

"Despite contacts between the Commission and the German authorities in the context of the infringement procedure, Germany has not taken any further steps," the European Commission said.

- R134a or R1234yf? -

Since 2013 EU regulations have demanded that car makers use a refrigerant called R1234yf on the grounds that it produces far less greenhouse gases than older coolants.

But Daimler is sticking to an older substance, called R134a, as it claims studies show the new one catches fire more easily and puts cars at a greater risk of explosion in case of a crash.

The makers of R1234yf, US chemicals giants Dupont and Honeywell, reject Daimler's claims.

Germany gave the auto giant special permission to keep using the older coolant, despite initial approval of the new one by the German Automakers Association, VDA, of which Daimler is a member.

The EU warned Germany in September 2014 that it could end up in court if it did not act.

"Despite contacts between the Commission and the German authorities in the context of the infringement procedure, Germany has not taken any further steps," the European Commission said.

Brussels dismissed Daimler's claims about the inflammability of the new coolant.

"These concerns were not shared by any other car manufacturer," it said, adding that they were also rejected by the German auto authority and the European Commission.

The case has caused tensions between Germany nd other countries on the continent over the way that the auto industry is regulated.

France's government controversially banned the sale of the latest models of some top-end Mercedes cars in July 2013 because they contain the old coolant.

The EU initially backed France and other countries supported an EU-wide block on the cars, but a French court overturned the ban a month later.