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starbuck88

Aux/Pusher Fan Not Working - M54 530i

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Hi All,

 

Strange one, or maybe it isn't. The short story is, A/C didn't work due to low refrigerant (last A/C gas in all the documentation appeared to be more than 11 years ago), All vac'd, pressure tested, leak tested and filled and now it blows lovely and cold.

 

However, this has highlighted that the AUX fan does not turn on. Whilst sat in traffic for a while, I felt this horrendous vibration, checked the Coolant temp and although the needle was pointing straight up, it was rather warm, the vibrating stopped when the a/c was turned off, turns out the line on the drivers side that runs past the wheel well was shaking violently. When driving the coolant temp came back down but I left the A/C off. Next drive out with everything cool, A/C worked with no vibration again. I think it over heated and the vibration was the high pressure (I believe the pressure coincides exactly with temperature).

 

So that points to 2 'issues' with the Aux Fan, Not only does it not come on when the A/C is on, it also doesn't come on when the coolant gets to a certain temperature. The viscous fan is obviously more than capable of keeping the car cool, as long as the A/C isn't on because I've had no issues in over 3 years with overheating etc.

This is the diagnosis so far, the aux fan seems to rock left and right every 10 seconds or so when the A/C is on but never actually carries on spinning. There are no fault codes listed for anything related to this (ISTA).

 

This is the later PWM style, I have so far taken off the connector and can confirm there is sufficient power (12v with car off, 14v with car running) and the PWM wire, you can see that fluctuating on the volt meter (I don't have an oscilliscope but reading forums etc as long as there is 'something' happening when the car is running (with a/c on) it appears to be sending the signal properly).

I believe with the PWM fan you can't just give the connector 12v and have the fan spin you also need to feed a pwm signal which I can't do... (I can't seem to find where in ISTA to force the fan on, any ideas?).

 

Does anybody have any further things to try, look for before shelling out what appears to be an extraordinary amount of money on a new fan assembly?

Kindest Regards

Edited by starbuck88

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Yes the later ones are PWM driven. There is a test routine for these in INPA, so Id be surprised if ISTA doesnt offer the same somewhere. Given the tests you’ve run sounds like its definitely the fan, as your tests have cleared the wiring & the ECU. Theres plenty of cars on the Facebook E39 For Sale page being broken, so you should be able to source a working secondhand one plus breakers on ebay. 

 

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I had the same issue and checked for PWM voltage the same way. As i recall, the controller and motor are a sealed unit so there's nothing else to tinker with. I shelled out for new fan assy at the dealer and it all worked as it should again. €220ish I believe.

 

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I've got exactly the same symptoms on my diesel with a PWM fan. I sourced a used one off ebay and have plugged it in to test it and it works so has confirmed my fan is dead. I've just not had the time to change it out yet.

 

 

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Managed to get a bit more time last night to diagnose. At the weekend I only had a few minutes spare to test the voltage and quick fault code read. At the weekend I cleared all the fault codes.

 

I re-scanned on ISTA and got this...

 

screen4.png

 

Woop, finally it had thrown up a fault.

I could then call up the ECU functions and try to activate the fan.....

 

Where it then did this:

 

 

 

So there we go. Fubard fan.

 

 

 

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