Your engine temperature sensor is responsible for relaying your engine temp to the ECU. Once the temp gets so hot, the ECU commands the radiator fan to come on. If your Golf has a bad engine temp sensor the radiator fan won’t know to come on, because the ECU won’t know how hot the engine is. You’ll need to locate and test the engine temp
Putting the air recirculation on would help a bit because the air the system.is cooling starts at a cooler temperature. And we refer to regassing the air con. It's gas at normal air pressure, but when in the pressurised system that is car air-conditioning, it's actually liquid. So it flows round the system.
18529 posts · Joined 2007. #6 · Apr 23, 2019. With ECON selected the air con is disabled and thus the fan doesn't come on. With ECON de-selected the air con compressor should engage and the fan should run to draw air over the condenser. If the fan is not running it's more than likely the resistor on the low speed circuit has burnt out.
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mk5 golf air con not working