Polo 9N3 radiator fan stage 1 issue

[S1ngler]

Hello everyone,

Recently, I've noticed that the cooling fan (the single large one in the engine bay, right behind the radiator) on my Polo 9N3 2005 1.4 TDI is not working in first speed. However, after some time when the engine heats up, the fan turns on normally in second speed.

Even though the VCDS shows that both speeds are functional (Coolant Fan Stage 1: ON; Coolant Fan Stage 2: ON) and proper voltage is present at the connector wires (the connector has 3 wires), the fan does not physically spin in first speed.

I’ve seen that this is a common issue in VAG group cars from that era, so I’m wondering:

- Is there a separate control module (physically detached from the fan) that regulates the fan speed, making it possible to replace just that part?

- Or is it necessary to replace the entire fan assembly (since the control module, along with the fan motor’s electronics, is integrated into the fan itself and cannot be replaced separately)?

[Johntheo1]

Can't attach a wiring diagran file but it may just be the contact in the thermo switch, easy enough to check if (speed1) resistor is gone in the fan, just short out the red permanently live wire into the thermoswitch with the red/black wire coming out of the thermoswitch, fan might then start in low speed, if so, just get a new thermoswitch. ( The other wire coming out of the thermoswitch, red/blue starts the fan in full speed, just give this a quick test as well to ensure you are connecting to the live wire coming into the thermoswitch)

For info here are the thermostat and thermoswith settings for my (family) 2005 Polo.
Thermostat begins opening at 84C. Fully Open at 98C.
The Coolant Temperature Indication is ECU conditioned before display to read a steady 90C
between actual coolant temperatures of 75C and 107C.
Fan Speed 1 ON at 91C to 97C. OFF at 91 to 84C.
Fan Speed 2 ON at 99C to 105C. OFF at 98 to 91C.