2003 Volkswagen radiator fan not coming on? - Volkswagen Cars & Trucks

Truly a ridiculous amount of electronics in this vehicle. Lots of fuses and modules for radiator cooling, but no relay. That means it is a function of the ECM and the 'modules'.

https://www.autogenius.info/volkswagen-jetta-2003-2009-fuse-box-diagram/

In earlier models it is located under the coolant reservoir. Videos in the link.

https://www.google.com/search?q=2008+volkswagen+jetta+radiator+cooling+fan+relay+location

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It may also be the temperature sensor.
Not knowing your model, if it uses both a belt driven and electric fan, the electric fan (or its sensor) may have failed.
Turn on the AC to see if the electric fan will cycle as it should since this is used (in most vehicles) for engine cooling if the main fan isn't adequate whether AC is in use or not.
On high mileage engines if distilled water was not used instead of tap water (along with coolant), the radiator core can eventually become clogged with calcium deposits. .

replace thermo switch... this is normally located near radiator hoses.

Make sure the air conditioner is not on. Otherwise the themostatic switch which controls the fan (located near the top radiator tank) will require replacing.

MOST OF THE TIME WHEN COOLING FANS KEEP RUNNING WHEN ENGINE IS OFF.ENGINE RUNNING HOT.YOU COULD HAVE A DEFECTIVE WATER PUMP.THERMOSTAT FAULTY AND THE RADIATOR CORE IS BLOCKED.CHECK GRILLE FOR RESTRICTION LIKE LEAVES AND OTHER DEBRIS.HAVE YOUR CAR HOOK TO A SCANNER THAT WILL TELL YOU YOUR COOLANT TEMPERATURE.THAT WAY YOU WILL KNOW ITS THE THERMOSTAT.

it has 2 get up 2 the themastat temp before fan works,hot air blows threw heater if not a curciut breaker for fan or motor on fan is bad.. system needs 2 be flowing water pump should be, with belt turning

CODE P2181 COOLING SYSTEM PERFORMANCE MALFUNCTION CONDITIONS - ECT SENSOR HAS FAILED. 2.0L ENGINE ECT LOCATION IS ON THE UPPER RADIATOR HOSE CONNECTION AT THE REAR OF THE CYLINDER HEAD. 2.5L ENGINE ECT IS ON THE UPPER RADIATOR HOSE CONNECTION ON THE CYLINDER HEAD ALSO.CHECK COOLING FAN FUSE AND RELAYS

make sure the cooling fan is working . its located next to the radiator fan.

there is a modual under the res with a blade fues in it. the modual and coonection rot due to coolant spills.great place to put them volkswagen

First you empty water, then remove fan, and radiator.
You need to follow the step by step procedure from a manual, buy the haynes manual for new beetle here is an example on ebay.
Replacing radiator is not a difficult operation, but if you do not do it properly you can damage your car, check that fan is working, water pump is running ok and that there is no leaking after doing the job.