It depends on the failure mode of the Aux fan to determine if the AC compressor will still energize. For my aux fan failure mode it was a catastrophic failure of the control board.

See my post on my failure mode along with pic of the fan forensic analysis.

http://www.xoutpost.com/bmw-sav-foru...fan-fault.html

As a service to this community I think Trader4 should perform a forensic analysis of his bad aux fan and post pictures to this forum.

:iagree:

I think his Aux fan electronics is fried. The result in his case is the onboard thinks it is working or at least responding back that it is allowing the A/C compressor circuit to engage. As has been mentioned before, as soon as the fan is disconnected, the A/C electrical circuit will not send out a signal and the compressor clutch will not engage, due to no aux fan response....

In the good old days you would just jump 12V to the compressor to confirm its ability to function. Now days all parts up stream must be working before system tests will complete.

Bottom Line: Install Aux Fan (pusher Fan). It is ONE part not as the OEM image show. See bottom photo for example. I have use the Brand: Mahle-Behr with good results.

This is just a test to see if the clutch engages and the system has the correct amount of refrigerant. You should not drive with the car set up like this since the system is designed to cycle off and on. With 12 volts jumped to the compressor, you eliminate the cycling of the system off and on. If he has a bad aux fan the high side pressure will build to the point that you can blow out the condensor coil or a refrigerant hose. The high side sensor prevent this from occurring, but it won't do this if you have the system jumped.

Another shade tree mechanic fix. Fix it right or don't fix it at all. From you previous posts I see that you are taking my advice about not fixing stuffs that breaks on your X.

I would test the fan before purchasing a new one. When you start the vehicle the aux fan is activated by the ECM for the purpose of diagnosing if the fan is working properly at 20% of max speed and then shuts it off. There is also a final stage power output on the fan housing that can also make the aux fan inoperative.

bcredliner

Can you post the steps to test the aux fan using the IMPA or other software, so the OP can get the right procedures? A few screen shots will help here also.
I do not think some of our newer readers understand that the on-board computer has built tests that will fire up devices, switches, sensors, relays, etc. All of which need a computer to send the signal not a $50 OBDII generic code puller.

Guys

The 12V jump to the compressor is just that, a quick test to confirm operation of the clutch and that the compressor will spin, regardless of line pressure and system functionality. NEVER run a car more than a few mins. As was mentioned above, this test bypasses everything to prevent damage to the system. Ice forming, over pressure, over heating, compressor damage, etc.

Question - does the AC clutch take a 12v feed? It is not unusual at all for automotive components in modern vehicles to use voltages less than 12v. Applying 12v directly to a lower voltage component can render it a paperweight.

I don't use the BMW INPA-DIS software unless I have no other option. I use it so seldom I have to start the learning curve all over again and that is not fun for me.

I would start with the easy stuff. I would make sure all associated fuses are good. Then I would start the vehicle and see if the fan goes through the test, starting up, turning slowly and then shutting off. If it doesn't I would ask someone how to use the software just as you have or go to the forum dedicated to using the software package.

More likely, I would pull the bumper and remove the fan as the most probable cause and bench test it to make sure it was the fan rather than a problem upstream.