Auxilary electrical coolant fan woes and possible electrical problem -

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Audi A6 The mid-sized Audi A6 model offers more room to the driver and passengers over the A4 line.

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Old 07-09-2010, 04:08 AM
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Join Date: Jul 2010
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Default Auxilary electrical coolant fan woes and possible electrical problem

I have been slaving over my 2001 A6 2.8L trying to get the electrical fan to work to put a stop to overheating problem and coolant boiling issue. The fan is definitely not coming on and I bridged the hi and the low connectors in the switch in the lower radiator hose and since the fan did not come on assumed I had a bad fan. I ordered a new fan and installed it and put the car back together and still the fan would not come on. I have now ordered and replaced the auxilary fan control module and I haven't been able to drive it yet but turned on the ignition and turned on the A/C (which I have read will turn on the electric fan) and still nothing. I have to replace the coolant fan switch because I lost the gasket that fits around it when I pulled off the lower hose, but I am trying to troubleshoot this without putting my car completely back together and potentially having to drain and replace the coolant, again.

One strange issue, which I am not sure would be related, is that when I turn the ignition on I can hear a little electrical noise, like subtle pops and what sounds like a small fan spin up for about a half a second. Then there is a quiet whining sound that lasts about 30 seconds before it subsides. I have been unable to determine what the electrical mechanism is behind the engine (between the engine and the battery directly on top) because the online manual that I purchased is a piece of crap. Is this normal or even potentially related to my problem.

The last issue I have is that I can not find out where the ambient air sensor that clips on to an extension in front of the power steering radiator and main radiator plugs into. I have the other end of that wire in the same location as the auxilary coolant fan termination which is in the housing right next to the power steering resevoir. I have searched high and low for its two pin male counterpart but I cannot find it anywhere. Does anyone know where the ambient temperature sensor terminates?

Thanks in advance.
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Old 07-09-2010, 02:58 PM
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Join Date: Sep 2004
Location: Newfields NH
Posts: 2,371

Small fan spin up -- most likely the fuel pump

Did you check the fan relays?
Do a search in this forum and see what I was told about checking them.

Hot wire the fans and see if they work.
Check the fan resistors - (in the left front fender well - just follow the wires back )

check the ground stud on the frame -- remove it and clean the connection..
1997 A6 Avant with over 250,000 miles - Now dead
2007 Dodge Grand Caravan SXT - 2002 Dodge Caravan
1999 Mercury Sable Wagon w/48K miles
1919 Model T Ford Beach Wagon - AKA Woodie
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Old 07-09-2010, 03:44 PM
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Join Date: Jan 2010
Location: Western MD USA
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Not sure about your fan problem but I am interested to know what you find out. I believe that one of the cooling fans is only supposed to operate for a short time after you turn the car off to help cool the engine when it isn't running.

Based on your description of the "little electrical noise and small fan spin", I vote secondary air injection pump.

good luck
2002 C5 A6 2.7TQ
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Old 07-09-2010, 04:36 PM
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Join Date: Jul 2010
Posts: 7

According to the online manual that I had the 2001 A6 had only two fuses that were located behind the driver's side storage (underneath the instrument panel). My car only had places for fuses in locations 19 and 21. Both of the fuses were the standard fuses and were in tact. If you notice the * it states that relays are in the control module in years 1999 and later.

Click the image to open in full size.

I have replaced everything else at this point. I picked up the gasket for the coolan fan switch today and will put that in line tonight and fill it up and test it. I will check the vehicle ground but I have no other electrical problems so I am no optomistic on that resolving my issue. I will put it back together tonight and see if I have any better luck tonight. I didn't know if anyone knew whether or not the auxilary coolant fan should definitely come on when I turn the A/C on even though the engine is not running.

I am still disturbed that i can't find out where the ambient temperature sensor terminates. I have the two pin female connector to the same location as the rest of my terminations for my auxilary coolant fan but there is no male connector in the vicinity. I can't find anything in my crappy online manual that shows where it terminates to, just where the sensor is mounted.

Click the image to open in full size.
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Old 07-11-2010, 09:07 AM
1st Gear
Join Date: Apr 2007
Location: Bronx ny
Posts: 240

Did you check that big 40 amp orange fuse under the dash?it's not those fuses u can see at the side but you'll have to drop the driver side bottom dash inorder to see the fuse I'm talking about
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Old 07-17-2010, 03:50 AM
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Join Date: Jul 2010
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Alright, I have finally gotten the car put back together, sort of. I decided to replace my driver's side drive axle but am battling a stripped 12 point bolt, therefore I can't drive it until I extract the bolt and get the axle back on it.

I started the car and turned on the A/C and now the electric fan comes on, the only issue is that when I shut the car off the fan shuts off. I can hear a slight hum coming from the area of the motor of the electric fan. It lasts about 3 to 5 minutes and then shuts off. I am assuming that the fan should be running on low instead of emitting a hum. Honestly though, there is a possibility that it could be the battery. I had to jump the car to get it started, the hood has been up for weeks and I'm not sure what else might be draining the battery. A weak battery would definitely create issues for the 12V fan but is there anything else that might cause this. Hopefully, I can drive the car for a while to charge up the battery and test my theory but until I get the drive axle replaced it is only a theory.

On a side note, the 12 point (triple square) 10mm bolts that attach the drive axle to the transmission are a major pain to get off. I might suggest an impact driver to anyone needing to get these bolts off so they might avoid going through what I am going through, trying to remove a stipped bolt with little accessibility and nothing to grab on to.
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Old 07-18-2010, 07:55 AM
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Join Date: Aug 2008
Posts: 418

The humming could be the auxillirary electric after run coolant pump running. They normally go 3-5 minutes after shut down. The fans may or may not run afterwards. All depends on the coolant temp.

A weak battery can cause al sorts of problems in the elctrical system, along with cause premature alternator failure (because it's working overtime to supply electrical power) and key-off, if the voltage is too low certain things will not work.
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Old 07-19-2010, 05:44 PM
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Join Date: Jul 2010
Posts: 7

Got the passenger drive axle on and took the car for a spin. The fan seems to be working, but I need to take the battery down to have it tested to see if it is taking a charge. The battery meter is around 14V so the alternator appears to be doing the trick but even after about 15 minutes of driving last night the car did not start. It had more juice than yesterday but not enough to fire the engine. I don't know if something is draining the battery or if it has just seen its day.

So it appears that the auxilary fan control module did the trick, as the car did not overheat. Now the power steering is acting a little wacky. I replaced the power steering pump and one of the hoses and topped off the fluid, but on my test drive I had intermittent failures. It is quite bizzare as it seemed to work for the first 10 minutes but as soon as I did a u turn it felt as though I had no power steering. I bled the power steering after replacing the pump and either way I don't think air in the lines would cause intermittent problems especially without any noise from the air in the lines. Oh well, seems to be my MO, fix one thing and break something else.
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Old 02-06-2012, 11:51 PM
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Join Date: Dec 2010
Posts: 6

Originally Posted by jj2345 View Post
Did you check that big 40 amp orange fuse under the dash?it's not those fuses u can see at the side but you'll have to drop the driver side bottom dash inorder to see the fuse I'm talking about
Can somebody post a picture of this fuse panel and where the hell it might be and to get to it???

I have a 1999 A6 Quattro and can not figure it out and or how to get to the fuse panel.

My Coolant Fan not coming on and I am thinking it the fuse.
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