Cooler Fan Always On: Troubleshooting & Fixes

Hello, recently, the radiator fan on a Golf 3 has been constantly running. Specifically, it activates immediately after the ignition is turned on and remains on for at least 10 minutes, even if the ignition is turned off immediately.
Volkswagen Golf 3, 1Z engine, manufactured in July 1996.
Is the fan also controlled by the engine control unit? Is there an external relay, where is it located, and what number might be on it? } Where could the cause be? }

Hello,

Please check the thermostat, which is screwed into the radiator.
If this keeps happening to you, you've found the problem.
To the best of my knowledge, the EDC (Electronic Diesel Control) does not control the radiator fan in any 4-cylinder TDI engine.
In most cars, there is either only a thermal switch or a thermal switch in combination with an additional control unit.

Best regards, Rainer.

Hi,
'Zitat:' translates to 'Quote:' in English.
'In certain models, the radiator fan has an additional function: to prevent excessively high temperatures in the engine compartment after the engine is turned off. To achieve this, the fan may run for up to 12 minutes at a low speed after the engine is switched off, to blow out the accumulated heat from the engine compartment. This is controlled by an additional thermostat switch and a control unit when the ignition is off.'

Source: Dieter Korp; 'Jetzt helfe ich mir selbst' Volume 155.

The location of this thermostat switch is at the coolant connection.
IMO, the problem is either with this thermostat switch or with the control unit for the fan after-run function.

@ Rainer:
How is the fan run time implemented when the air conditioning system is turned on? Is it through the EDC (which knows whether the AC is on or off), or perhaps through a direct connection from the compressor connection to the fan control unit, utilizing the relay built into the unit?

Best, Andy.

Rainer K. wrote:

To the best of my knowledge, in no 4-cylinder TDI engine does the EDC control the radiator fan.

Hi Rainer,

Actuator diagnosis in VAGCOM: including, for example, the relay for the after-fan (at least in the AFN engine).

The relay is connected in parallel with the thermostat switch in the radiator.
If there is something that needs to be cooled down, the EDC draws power through the relay 109 that it activates itself and controls the fan relay until the heat buildup is gone.
"How long it takes is, as far as I know, calculated from the operating conditions of the last few minutes before it was turned off (engine load, temperature, etc.)."

Hello Ulf,

I learned something new. With my car, the radiator fan never showed up during the actuator check...

Best regards, Rainer.

Thank you for the tips. I will follow this approach and report back here with the outcome.
Okay, just to let you know, there is a thermal switch located near the upper water fitting.
See you soon, Gerrit.