Cooling System - Cooling Fan Runs Continuously
01 Cooling Fan Remains Active When Vehicle is Off80 08 04 2016135/3
November 20, 2008
Supersedes Technical Service Bulletin Group 80 number 08-02 dated April 22, 2008 for reasons listed below.
Vehicle Information
Condition
Customer may report that the cooling fan runs continuously.
Technical Background
If both cooling fans run at full speed immediately after engine start (irrespective of engine temperature), the fan control unit is in emergency mode. After switching off the engine, the cooling fans run for a few minutes (15 max.) until the engine control unit goes into rest phase and removes the voltage supply to terminal 15 of the fan control unit. The emergency operation occurs if:
- The engine control unit doesn't know the coolant temperature (fault memory entry), e.g. because the temperature sensor is inoperative and therefore cannot tell the fan control unit how quickly the fan should operate.
- The data cable between engine and fan control unit is disrupted.
- Because of a high load (or a problem with engine cooling) the engine has reached such a high coolant temperature that both cooling fans run correctly at their highest speed.
Production Solution
Not applicable.
Service
1. Check the communication between the two control units with the final control diagnosis for the cooling fan. If the data cable is disrupted, the final control diagnosis doesn't work.
With a dead battery (breakdown) because of a cooling fan that ran continuously even with the ignition switched off, check for the source of the cooling fan activation:
1. Switch the ignition off.
2. Remove the 5 Amp fuse S4 (Figure 1). (Note: The designation S4 may differ depending on model year or version. Check the current flow diagram).
3. If the fan(s) stop, they and the control unit are functioning correctly. Replacement of the cooling fan and/or control unit is not required. The fan runs because of one of the points listed in the Technical Background.
4. If the fan continues to run after removing the fuse, there is a fault (short circuit) in the cooling fan control unit, not on the fan itself. Replace the fan control unit.
Warranty
This TSB is informational only and not applicable to any Audi warranty.
Additional Information
All parts and service references provided in this TSB are subject to change and/or removal. Always check with your Parts Department and service manuals for the latest information.