Stop and go traffic is a different condition than idling. In stop and go traffic, you are behind another car which blocks fresh air and possibly raises the temp at the front of the aux fan. So you can expect better cooling efficiency at idle than in stop and go traffic. Also make sure your aux fan is turning in the correct direction. If you us a small piece of newspaper and bring it close to the aux fan in the front, the paper should get sucked in as opposed to being blown away. The air must flow from outside to inside the engine compartment.

How many pins are on your temp sensor ? Three ? On my car, I have a single pin connector for Klima relay and a seperate two pin connector for the aux fan.

You can try shorting the two pins that belong to the aux fan relay on the same temp sensor from which the Klima relay gets its input (the one pin you disconnected). The aux fan should run right from the very beginning, when you start the car. This should keep your car cool all the time.

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Saumil S. Patel