Radiator fans wont come on

[dubblrest1985]

I turned my ac on so the fans would come on. then played with the fuses and relays in the under the hood "fuse box".

[audiqv8]

Originally Posted by dubblrest1985

around it.. I tried replacing the sensor on the bottom drivers side of the radiator. Both high and low speed works, just will not come on when the engine temp gets too hot.

Verify that you don't have a clogged radiator. The sensor at the bottom of the radiator will not see an overheat condition if it is clogged. While driving on the highway does the temperature remain normal, but start to climb when the car isn't moving? This will also indicate that the radiator is clogged.

[sugaryling]

Originally Posted by audiqv8

Your car have a fan controller/resistor

V7 are the two fans
J26 and J135 are the relays
J135 relay is for high speed as you can see that it bypass the fan controller/resistor
S42 is a 40 amp fuse which is a rather larger fuse and will not be in the regular fuse box
N39 is the fan controller/resistor

Check fuse S42 to verify that it is good.

Thanks, this explains why I can;t find the fan controller like in my C5 A6.
At the fuse box under the hood, next to the firewall, there is no 40 amp fuse. Just a few 30amp fuses.

[audiqv8]

Originally Posted by sugaryling

Thanks, this explains why I can;t find the fan controller like in my C5 A6.
At the fuse box under the hood, next to the firewall, there is no 40 amp fuse. Just a few 30amp fuses.

How do I know which relay is J135 and J26? It's not labeled "J26." However, there are numbers next to the relays. Number from 1-20 something I think.

Fuse S42 is an inline fuse. BTW this electrical diagram is for a C4.

[sugaryling]

Yes, I am working on a C4. I was just referring to how the C4 has no fan controller like in my C5.

Do you know where I can find the S42 inline fuse? I followed the fan wires but it just disappears into the chassis at the firewall. I assume it goes into the fuse box at the firewall.

[audiqv8]

The fuse is located behind the storage compartment on the driver side underneath the steering wheel. Yes you will have to remove the storage compartment shelf.

[audiqv8]

1 open
2 Second Speed Coolant Fan Control (FC) Relay
3 Coolant Fan Control (FC) Relay
4 open
5 open
6 open
7 open
8 open
14 Power Seat Circuit Breaker 1, Driver's Seat
15 Fuse for luggage Compartment Socket
16 Power Window Circuit Breaker Front
17 Power Window Circuit Breaker Rear
18 Fuse 1 for control module - ABS
19 Coolant Fan Fuse
20 Coolant Fan Fuse
21 Control module fuse for coolant fan
22 open
23 open
24 Power Seat Circuit Breaker 2, Passenger's Seat

[upallnight]

Originally Posted by sugaryling

Do you know where the controller is located? How about the fan switch? I think I'll start with that first since it's about $10 sensor.

It is located on the driver side between the front tire and the bumper. The only way to get to it is from underneath the car. The positive side wires for the fans are connected to the controller and the negative side wire is connected to a ground that is located at the topside of the engine bay.

[dubblrest1985]

Originally Posted by audiqv8

Verify that you don't have a clogged radiator. The sensor at the bottom of the radiator will not see an overheat condition if it is clogged. While driving on the highway does the temperature remain normal, but start to climb when the car isn't moving? This will also indicate that the radiator is clogged.

That is exactly what happens.

[sugaryling]

Originally Posted by audiqv8

Most likely your "Radiator Fan Controller/Resistor" is shot since aux fan should start when the AC is turned on.

I don't know why I said that my fans don't come on when I turn on the AC but they do now! I must've looked at it briefly or forgot to hit the AC button and just turn the temp down. Regardless, both fans com on when I turn on the AC.