reddevildemo

Hi all, new 2002 Allroad 2.7 owner here with a few questions.
I have read the posts and the tech right up on the fan issues but I am still not sure about them.

Today, drove home from work w/AC on, car up to temp (water temp needle center, oil a bit below center). I wanted to see if my fans are working correctly, pulled into garage, turned off AC, left engine running and popped the hood....neither were on. Both the fans spin free by hand with no noticeable noise or interference.

Questions are, with AC on which fan should be running, the one next to viscous or the one outside engine bay? When does the other run? Is there supposed to be an after run feature on these?

Thanks for helping out a newb to Audi

-Darin

P4Ring

I can only tell you what I know. There should be no after run. After run is normally for transverse mounted engines. (side ways) The allroad engine is mounted longitudinally (North-South) It has a viscous fan clutch/fan that continuously run with the engine and engage by temperature.

When AC is on the fan in the back will run if engine bay is hot. (for example if you just start up the car and the engine is cold, it does not run right away. The fan in front do run also, but I am not sure when.

The car will not be back until Thursday, so I cannot help any further.

GTA_Driver

The main, viscous fan should always be running. When it's not "on" it still should turn, freewheeling.

P4Ring

Put it another way.

Viscous, from the word viscosity (having a glutinous consistency and the quality of sticking or adhering: eg. A viscous flow) is the fact that the fan clutch is engaged when the engine compartment temperature rises to a specific degree. If its not engage the fan will free wheel but not necessary put a load on the engine.

The clutch is the inner piece made of aluminum (with fins to better sense temperature) It work just like your thermostat. A type of wax inside will expand when heated thus pushing the clutch to make contact. At this point the engine drives the fan and it no longer in "free wheeling mode". NOTE: Due to the viscosity of the fluid inside, it feels slightly stiff when you rotate the fan at cold temperature. (cold here mean room temp to activation temperature) This reason, and the laws of physics make the fan spins all the time. The amount of torque applied to it depends on if the clutch is engage or not.

Sorry for the lecture, but he/she was asking about the fan in front of, and rear of the radiator.

reddevildemo

Thanks everyone. Found out all is working as should with AC on all runs run when car up to temp. Everything free wheels as should when car is off.

Thank you all very much for the info and help.