So here is the run down of the issue(s):
Car is 2001.5 B5 S4 Stg3 … all stock fans still in place including mechanical fan. Intercoolers are ER so no blockage at the radiator.
Small electrical fan in front of radiator is not turning on without the A/C being on. With the A/C on all fans work and turn on including the small fan.
Outside temperature during testing 50deg F - 70deg F.
Ever since i bought this car a few months ago i’ve noticed that the mechanical fan/fan clutch seems to be working a lot. When the car is started from cold the mechanical fan is off and everything is normal. It takes about 5-10 mins of driving to get it to operating temperature and it never overheats while moving. Once the engine is at operating temp if i hit a red light and sit for a few minutes the fan clutch will engage and the car will sound like a semi upon take off through 1st and 2nd gear and then it will be back to normal… until the next stop light where the same thing happens.
Also, after shutting the car off if i come back within 10 minutes and start it , the coolant temp gauge will be just a slight tick over the half way mark but if the engine is started the needle will go back to the half mark within ~30 seconds.
Taking measurements with the secret climate control unit menu i am seeing that the coolant temperature while cruising on the freeway is 95 deg C and around town it stays about the same with spikes to 96-98 deg C when idling for a few minutes or while being stopped at a light. If i idle more than that the temperature would creep up even more.
Oil temperature runs about 215-225 deg F on the freeway and about 215 deg F around town.
Scanned with VAGCOM and no codes were present.
Mechanical fan works well as evidenced by the semi truck sound when coolant is ~95deg C and above. Small fan in front of the radiator does not turn on unless the A/C is on. Same with the other electrical fan on the inside of the radiator, next to the mechanical fan. When the A/C is switched on, both electrical fans come on. Aux pump is new, and i just replaced the coolant temp sensor and AUX FAN sensor in the lower radiator hose. No change, everything the same as above.
What temperature should the small aux fan in front of radiator should be turning on? I know the fan is working because it comes on when the A/C is switched on but my research says it should be running when the coolant temp goes above a certain point in order to assist the mechanical fan in cooling the car down.
suggestions or info would be greatly appreciated.
thanks for reading.