The fan is not m3 specific. There are two fans one from Bosch with straight blades and another from Magna with curved blades. Get the curved blade model it run quieter than the Bosch and I think moves more air. As stated you want to know why your fan is malfunctioning before just replacing it.
The Bentley manual says that you drop the radiator to change the aux fan but we removed the bumper, driver's headlight, and front air dam to accomplish the same install. Not sure which is easier.
I went the Autobahn salvage route for $100 pre-tested and warrantied for 30 days but the same fan from Crazy Rays here in MD would be $25 with no testing or guarantee and your labor to pull it.
|Troubleshooting the aux fan.
1. Pull the K1 (normal speed) and K6 (high speed) fan relays from the fuse box.
2. Check for voltage on socket pin 30. It should be hot at all times.
3. Turn the ignition to run and check for voltage on both sides of fuses 19 and 20. The voltage should be essentially the same on both sides of the fuse. If not, replace the fuse.
4. Jump the wires on the radiator temp switches.
If you have 2 switches:
a. Jump the normal speed switch, green/black to black and check for voltage at socket pin 85 of the K1 relay. It should read 12V with the ignition in run.
b. Jump the high speed switch, green/black to black/brown and check for voltage at socket pin 86 of the K6 relay. It should read 12V with the ignition in run.
If you have the dual switch:
The wire colors are the same. You just need to jump them in the 3 pole connector. Pin assignments are as viewed from the connector face.
Pin 1 (across from flat side) should be green/black
Pin 2 (across from key) should be black
Pin 3 (remaining) should be black/brown
5. Replace the relays and redo the temp switch tests. The fan should come on in normal and high speeds.
If high speed does not come on:
With the aux fan high temp (green/black to black/brown) switch jumped, check for voltage on both sides of fuse 18. If you have no voltage, the K6 relay is suspect. If there is any appreciable difference across the fuse, replace the fuse. Check for voltage at aux fan on the red wire. If you have no voltage, there is a wiring fault. If you have voltage, the fan or ground is suspect.
If low speed does not come on:
With the aux fan low temp (green/black to black) switch jumped, check for voltage on both sides of fuse 3. If you have no voltage, the K1 relay is suspect. If there is any appreciable difference across the fuse, replace the fuse. Check for voltage at aux fan resistor on the black wire. If you have no voltage, there is a wiring fault. If you have voltage, check for voltage on the aux fan red wire. It should be less than 12V. If you have voltage, the fan or ground is suspect.
Finally, we need to check that the AC can engage the normal speed fan.
Remove the K1 relay. Turn the AC on and test for voltage on socket pin 86. If there is no voltage, then there is an HVAC problem.
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