Question about 2004 Audi A4

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Audi a4 2002 radiator fan keeps randomly starting

When i switched off my car the other day, the radiator fan came on. it went off when i switched the ignition on, but seems to have started in the garage and drained my battery completely. can anybody point me towards help please? thanks

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  • Anonymous Mar 13, 2014

    my radiator fan starts upon i turn on ignition switch



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  • 64 Answers

It could be a faulty fan switch, or faulty engine coolant temp sensor or a faulty fan relay

Posted on Feb 18, 2009


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There is 30amp fues over the battery that needs to be checked and also, a good way to check the fan is to bridge the connectors from the radiator temperature sensor. Its attached to the bottom left of the radiator. Has 3 wires. bridge them in different configurations. one set is for high speed and the other is for low speed. Its quite common for the low speed resistor to blow.

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Before you replace check to test the car when idling. let the engine build up heat and test the engine temp. if the fan is not activating and shutting off accorrdingly then only you need to check for the thermostat. Since your car is overheating it means that your fan is not working at all or cutting off fast. Insuch a case you can go ahead. But if the fan is working fine and the AC is also switched on, then if the heat goes up, you will need to check for the radiator having any blocks. Check to see physically for any vent blocks on the fins reducing the air flow. even is any paper is stuck this can make the temp go up even if the fan is working. use a good pray washer to clean the radiator. if not flush your radiator and check for rust in system. if all this is not giving any result check for the engine management, for fault in the tining system. The fault should be here. but make sure before you drag to the traffic to test for a long duration idling with the AC put on.hope this is helpful. good day

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1 Answer

I have an Audi A4 1.9TDi 2004. I was driving a distance of 25km and the car temp gauge went up twice on the journey and I got message on the dash COOLANT with a pic of a thermometer. I then drove 80km...

Make sure you uhave a good mixture of antifreeze it make the boiling point higher as well as the freeze point lower. Check the fans let it idle turn on the ac and wait and watch.If it gets hot and No fan comes on start there / thermastat The t-start should be open around 160-180 degrees you should notice it get to the threshhold then drop 10 degrees / heads check for water in the oil oil in the water .See if you can get a temp gun if every thing else checks good before you get into the wiring.

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Audi a3

Does it keep running till the batt is flat? It could be the aircon condenser fan running - on the left as you stand in front of the car. This is a common prob with A3s of this age.
I have a '05 3.2L Quattro V6 and suffered the same prob. The batt is in the boot of the V6 and is sealed like Fort Knox so impossible to disconnect. After about 3 days with this the fan running constantly and having to put a charger on it every night I let the batt run completely flat to try and reset the complete system - no DIS lights - no starter motor clicks - DEAD. Then I jump started it and the prob disappeared completely. Everything is working perfectly ncluding the aircon. That was 4 days ago and 'touch wood' I've had no probs since. I know this won't work for everyone but it's worth a try before forking out £300+ for a new condenser fan unit. Good luck!

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1 Answer

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check the radiator.for leak. or resovoir. If its rusty, and color of water is not a fine blue/red etc. you may need a new one

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1 Answer

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Electric fan on the radiators since 1980. Would be worried if not kicking in. Fuel cap? Other problem. Go ask for a litle check up
with reputable dealer. German cars break down more often then japanese. Fact. Unless Mercedes.

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2 Answers

Over heating, and no AC

Cooling Fan Malfunction. Your radiator fans are most likely not working. That's why the temperature is OK when you're driving full speed and the wind is cooling your radiator. You need to check and/or replace your cooling switch module and radiator fans (most likely it's the cooling module). If you were sitting idle or in stop-n-go traffic for an extended period of time, your car WOULD overheat because the fans aren't kicking in cooling your radiator - then you would see all of the cooling system water spill out of the coolant reservoir, before this would happen your temperature gauge would go to the red and the digital dislpay would flash a thermometer (indicating you're about to overheat in 2 mintues). I hope this helps someone out there - Yes, it happened to me in the middle of nowhere.

Jun 25, 2008 | 2002 Audi TT

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