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Billy, Trainer/Master tech.
Category: UK Car
Satisfied Customers: 3498
Experience:  Trainer - master tech., SAE member
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Audi A3: Billy, my 2004 3.2 quattro the fan runs until it

Customer Question

Hi Billy, my 2004 3.2 quattro the fan runs until it flattens the battery but seems to be ok for a few days after you have taken it on a long run and got the temp up to 90 but it takes about 10 miles to do this
Submitted: 2 years ago.
Category: UK Car
Expert:  Billy replied 2 years ago.
Hello and Welcome! I'm Billy and i will assist you with your inquiry. Feel free to ask if any further info is needed.
It takes 10 miles for the temp to get to 90?
is the engine overheating?
do you have any other problems or symptoms?
Customer: replied 2 years ago.
No engine not over heating, if you only go on short journeys ie to the bottom of the drive the fan runs hard for 5 to10 minutes. Thus too many short journeys and the battery is flattened
Expert:  Billy replied 2 years ago.
does the fan start at full speed, after engine is started, before the engine is warm?
Customer: replied 2 years ago.
Expert:  Billy replied 2 years ago.
If the fan(s) run(s) 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 (which does not seem the case you have).
Can you access a scan tool, so we check if the coolant temperature sensor is causing this? as next we need to check the wiring to the fan module, and if all are good, the fan control module requires replacement.
Customer: replied 2 years ago.
Is it hard for a non mechanic to change the temperature sensor and or thermostat, I did have this problem about 4 years ago and they changed both of the fans! is that what you mean by fan control module.
Customer: replied 2 years ago.
I don't have access to a scan tool
Expert:  Billy replied 2 years ago.
I would not recommend replacing the temperature sensor or the thermostat (the thermostat is not very likely to cause this) before at least checking them (the temperature sensor is most easily checked using a scan tool.
On some variants the fan control module is within the fan (integrated), which seems to be your case. On others, the fan control module is at the bottom of the radiator on the inside of engine bay.
Kindly get back to me with your findings, or if further assistance is needed, so we proceed accordingly.