A6 2.7t and S4 - Excessive A/C fan noise solution long
10-04-2001, 09:04 AM
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A6 2.7t and S4 - Excessive A/C fan noise solution long
I suspect there are hundreds if not thousands of 2.7 A6's and S4's with this screaming A/C fan problem. Dealers may try a new A/C fan or just send you away with a "they all do that." Do not settle for a "they all do that" response, if you're A/C fan screams. Every dealer should contact any customers who complained about excessive fan noise and fix the problem. From other posts, some dealers have replaced the fan control module to fix the problem.
But, why does the fan control module go bad?
There is a rubber sealing strip about 2"x18" that goes between the radiator and the electric cooling fan on the back of the radiator(not the A/C fan). This strip comes loose and gets sucked into the fan(or falls into the dustshield pan, if you're lucky). If it gets sucked into the fan, it either restricts or jams the fan. This in turn damages the control module and disables the cooling fan. Because the control module operates both the cooling fan and the A/C fan, when there is no longer a load from the cooling fan, the A/C fan screams.
First check that your cooling fan spins freely. If it's jammed or hitting something, you can pull out the offending rubber strip by removing the turbo pipe above the fan so you can reach down to the fan. Two hose clamps and one bolt to get the pipe off. Chances are your fan will not come on at all even though it now spins freely. However, it may come on after an hour or more of idling, because the high temp control circuit is still OK, while the low temp circuit is shot. Techs do not like to go through the trouble shoot procedure, so they idle the car and if the fan eventually comes on they send you home...still with a screaming A/C fan. The fan control module is mounted on the frame and is a pain to replace, and further, the connecting harness has to be threaded up through a very tight space. Bottom line is that the techs hate it.
To check the control module, you jump the holes in the temp sensor plug to simulate either a low temp or a high temp condition to turn on the fan at low or high speed corresponding to the temp signal. The sensor is located in the lower radiator hose on the passenger side. You can easily get at the plug from beneath the car. Drop the dust/noise panel and you can reach up and unplug the connector. The connector has 4 holes, jump 1 and 2 for low speed fan operation and 3 and 4 for high speed fan operation. You will probably get no fan despite having 12 volts at the connector holes.
The control module gets damaged because there is no fuse between the fan and the module. Since the module blows first, the fuses are well protected by your control module! Nice going engineers!!! Ever hear fo a fusible link???
If you want to check the fuses anyway, there are two of them located directly below the relay panel that holds the 605 relay. It's under the dash and you have to remove the panel for access as described in the 605 relay technical FAQ. There's another fuse in the fuse panel, but it will be OK.
You can also check the fan motor by running 12 volts directly to it. Just follow the wires from the fan up to the connector panel over near the driver's fender under the flat top plastic cover, which just pulls off. I used a battery charger to power my fan.
But, why does the fan control module go bad?
There is a rubber sealing strip about 2"x18" that goes between the radiator and the electric cooling fan on the back of the radiator(not the A/C fan). This strip comes loose and gets sucked into the fan(or falls into the dustshield pan, if you're lucky). If it gets sucked into the fan, it either restricts or jams the fan. This in turn damages the control module and disables the cooling fan. Because the control module operates both the cooling fan and the A/C fan, when there is no longer a load from the cooling fan, the A/C fan screams.
First check that your cooling fan spins freely. If it's jammed or hitting something, you can pull out the offending rubber strip by removing the turbo pipe above the fan so you can reach down to the fan. Two hose clamps and one bolt to get the pipe off. Chances are your fan will not come on at all even though it now spins freely. However, it may come on after an hour or more of idling, because the high temp control circuit is still OK, while the low temp circuit is shot. Techs do not like to go through the trouble shoot procedure, so they idle the car and if the fan eventually comes on they send you home...still with a screaming A/C fan. The fan control module is mounted on the frame and is a pain to replace, and further, the connecting harness has to be threaded up through a very tight space. Bottom line is that the techs hate it.
To check the control module, you jump the holes in the temp sensor plug to simulate either a low temp or a high temp condition to turn on the fan at low or high speed corresponding to the temp signal. The sensor is located in the lower radiator hose on the passenger side. You can easily get at the plug from beneath the car. Drop the dust/noise panel and you can reach up and unplug the connector. The connector has 4 holes, jump 1 and 2 for low speed fan operation and 3 and 4 for high speed fan operation. You will probably get no fan despite having 12 volts at the connector holes.
The control module gets damaged because there is no fuse between the fan and the module. Since the module blows first, the fuses are well protected by your control module! Nice going engineers!!! Ever hear fo a fusible link???
If you want to check the fuses anyway, there are two of them located directly below the relay panel that holds the 605 relay. It's under the dash and you have to remove the panel for access as described in the 605 relay technical FAQ. There's another fuse in the fuse panel, but it will be OK.
You can also check the fan motor by running 12 volts directly to it. Just follow the wires from the fan up to the connector panel over near the driver's fender under the flat top plastic cover, which just pulls off. I used a battery charger to power my fan.
10-04-2001, 10:49 AM
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Re: My 2.8 has done this since day one
I'm not sure if 2.8 suffers from the same rubber seal problem, or if it has the same fan configuration. The fan that screams on the 2.7 is the one in front of the radiator. Nevertheless, I suspect that any fan that screams like Art Arfons' "Green Monster," has a control problem.
10-04-2001, 11:31 AM
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You're right. They had to replace the fan control module on my '00 2.7T
I was in the shop when the tech pulled out the piece of rubber that had come loose. As soon as he heard the noise, he knew how to fix it- i.e. not the first time this has happened. Been fixed now for 6 months, and haven't had the airwarning siren throughout the entire summer.
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10-04-2001, 12:12 PM
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Same symptom, different cause
I just recently took my 2001 2.7T in for it's first year service. The fan-siren noise had started about a month prior. First they replaced the main fan. Then they replaced the auxilliary fan. Then they replaced the control module. Finally they looked (!) and found a burned-out wire (leading-to or coming-out-of the control module, I assume). I should be thankful they at least got it fixed, but I've noticed a few more creaks and groans in the dash/pillar area since they did all that dinking around.
10-04-2001, 12:48 PM
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Re: Same symptom, different cause...maybe same
I'll bet they never told you about the rubber strip, and perhaps the burned out wire and/or the control module was caused by the jammed fan in the first place.
