slow784

I have 99.5 A4 2.8q and I am having problems with what I believe is the secondary air pump. On cold days after short drives there is an electric fan or motor that comes on after the car is turned off. The noise seems to be coming from the front passenger side under the air filter. The motor will continue to run off and on for several hours. This has always been just an annoyance, but today the car wouldn't start. As soon as I hooked the battery charger up to the car, the fan came back on and stayed on. If you have any advice I would greatly appreciate it. Thanks

ModifiedA4

im pretty sure the relay for the secondary air pump is in the ECU weather box, that is where it is for my make and model.

i'd replace the relay.

ModifiedA4

though, i have gone through 3 combi valves so far!

quattrokiwi

it could be the after run coolant pump which is under the air intake. This is controlled by the fan control module under the drivers side frame rail at the front.
To eliminate this option pull the 40 amp fuse under the knee bolster, its at the back below the relays, if the noise stops, there's your problem

ModifiedA4

usa b5 A4s do not have an afterrun system.

ModifiedA4

<ul><li><a href="https://forums.audiworld.com/a4/msgs/2242304.phtml">here, i did it for you</a></li></ul>

BeetleB

Agree sounds like secondary air pump relay part# 141-951-253-B

quattrokiwi

mines a 99 2.8 in California, with what the factory calleds heavy duty cooling.
i had to replace the control unit becasue it runs the electric fan on radiator as well.

ModifiedA4

interesting, your a4 is relatively rare.

quattrokiwi

it made me scratch my head for a while when trying to figure out why my electric fan wasn't running. I was looking for the resistor, intead of the control box.

here old and new

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