2004 AUDI A8- radiator fans on all the time!!
 

Anyone know what might be the problem for my radiators stay on all the time.Engine temperature seems to be normal only one time was little higher.
Those fans are on all the time.
Thermostat??? (indy say is 6 hour job to replace)
Fan control module??


Any advice is apreciated!!

2 radiator fans..one mechanical, one electric.

Normal is :

1. Mechanical fan (runs off belt) ALWAYS ON when engine is running...runs faster as engine heats up by way of a viscous clutch (liquid thermo coupling).

2. Electric fan runs ALL the time if climate control is ON and key is ON, engine running or not..all weather...engine, air cold or hot. This is to ensure that the AC refrigerant is cooled...AC cooler is connected to the radiator (in front of it). If climate control is OFF, electric radiator fan only runs when engine temp gets higher...it's 2nd purpose, to help radiator cooling in hot conditions...normal.

If engine is at cool or just normal temp, turn off the climate control completely (fan control turned to "0" will shut it off). Electric radiator fan should turn off, unless engine is above a certain temp. Best time to check is with cold or just warmed up engine.

NOTHING wrong with fan control module, unless the above is not the case.

If your temp gauge stays near the normal setting most of the time (first thick mark) and only goes a little higher (no where near the red) in hotter or sitting/idling conditions, there is NOTHING wrong with the thermostat.

And yes, if the thermostat needed changing, it's expensive(the labor, not the part). It is buried deep under the timing belt. If your car has between 70-100K miles on it and has never had the timing belt changed, it is probably time....esp nearing or over 100K miles. The thermostat and water pump should be changed at the same time, whether they have failed or not...the labor is the biggest part of that job, not the cost of the parts.

Timing belt was changed from prevous owner and i asuming the water pump and thermostat as well.
I understand the fans be on but in my case they running hih and very loud with no difference if i turn of a/c or not.
Car have 90 000 mls.
I think module?

Thanks in advance!

Yes, possible,
BUT, also possible that "Coolant fan control thermal switch" (back lower right on radiator...where it is on D2) is stuck on. It sends 2 different signals to fan control unit...off when cool & normal, low speed and high, depending on higher coolant temps. Your car definitely has one...I looked up the part. If it was stuck on high, you would get the same result...fan on high all the time. It's a very cheap part compared to the control unit.

I would unplug the wire connector at the thermal switch and test (check if fan still runs full speed, when not needed?), before assuming the control unit...about the only other thing that would cause this...actually more likely.

Control units usually just stop turning the fan when they go bad...I have personally never seen a failed one send a high fan signal by itself...but it is possible(?).

If the problem continues without the thermal switch connected, then it's probably the control unit.

silverd2: Ok...sound good..I just droped off my car to my indy and i should know today whats is wrong.I will post the result.This morning when i started the car to drive to indy the fans was normal while car was cold but after little driving they go high again.
Other question i have..do i need reset anything thru VAG-COM if replacing battery?
battery show me in MMI that is completely low but still starting the car normaly.I did not change the battery yet.Just wanna verified if i need after replacement reset the batery meter.

On earlier models, all resets can done by owner, with car's controls. Radio needs to be recoded with radio controls...owner manual has code and procedure. If you don't have the 4 digit code, it could be a problem. ECM is readapted on first start...hold key at ignition position for 5 seconds before start. Window controls (auto one touch up/down) readapts by holding window switch in place at up position for a few seconds till it reinitiates...then check.
Clock/date and seat position memories will likely need to be reset also.

All this assuming the D3 has same procedure as D2 A8....lilkely the same. If you have the owner's manual, it will include battery replacement procedures. If no manual, you can buy them from various sources online...Bentley publishing, for instance.

i have manuals..

ok....just have call from my indy and they say i need new fans because the control module and resistor is part of fan and cannot be purchased separately.
I need two fans bassicaly one cost $560 and labor $500.So out of the door $1800.
Jeeeeez...the say i can drive just the fan is loud..

I'm not there, but I think you have been taken. I don't have a manual for your model, but the one fan that has control unit built in is $420 from:

http://www.genuinevwaudiparts.com/pa...?siteid=214407

I can NOT image why they would be replacing the other fan too...makes NO sense.

Plus the $25 thermal switch could be causing the problem.

And $500 labor?! Did they explain that?

If you actually trust them and are made of money, then I guess I feel no sympathy. I could be wrong, but I don't think so. I just wish one of the Audi techs on this forum would chime in.

yea would be nice if tech will chime.
I know them....they say the other fan might be unnesesary to change.Also the control module is part of fan from what i understand and cant be ordered separately.