AC failure diag help. The saga continues.

[Bdc101]

Hi all,



Thanks for all the help you guys have given me so far (clavurion, overboost, andrewwynn, upallnight, etc)



Last week I found that the AC is not turning on because the DME is registering an aux fan fault.



I was able to find a used but good aux fan, plugged it in, and it did not operate. I cleared the fault, and it came back.



I checked for voltage at the aux fan connector:



https://www.newtis.info/tisv2/a/en/e...ic-fan/o65COqX


Terminal 4 (big wire, red w/ blue stripe) should have battery voltage but has nothing. It comes directly from fuse F61 in the glove compartment fuse box. I checked the fuse and it is good. I also checked it with a DMM and it has continuity. Then I turned the car on and confirmed that it does have 12 volts on both sides of the fuse. Still, nothing at the connector in the engine bay.



Newtis shows this connector X10455 as having the red/blue wire in question, but the only wires coming out of it are red. The one next to it (X10454) has one red/blue wire. All four of the wires coming out of it have 12 volts.



https://www.newtis.info/tisv2/a/en/e...0i-sav/UnTx4fi


The first wiring diagram above shows a continuous wire going straight from fuse F61 to my connector. But clearly that is not the case. It's not the same color wire. But even if it was mislabeled and it was actually on X10454, I don't get continuity to any of the four wires shown on the two connectors in this diagram.



I'm super confused now. How can I have no blown fuse, power at the wire on the glove box side, and nothing on the connector side? If it had a short it would have blown the fuse. There is maybe 5 feet of wire total, and the only place I can't inspect it is where it goes through the firewall.



One other thing to note is that the red/blue 12v wire to the fan is indeed skinned at one bend. It doesn't show any signs of arcing or burning, and it looks like it's been that way for a while. I can't see why that would cause the problem though, because the fuse is not blown.



Is there ANY reason why I wouldn't get 12 volts at that connector?



I did find at least one other aux fan issue just like this while searching, but no resolution.



Where could I possibly look next? The only thing I can think of is running a new wire from that fuse to the fan.

[upallnight]

You have a break in the wire from the fuse box to fan. Because of this break the fan isn't spinning and when the DME command the fan to spin but it doesn't, it can't send back a voltage to the DME that the fan is good. The fan may still be good but because it can't spin due to no voltage at the connector, the DME just assumes the fan is bad hence the Bad Fan Fault. You can run a new wire from the fuse to the fan.

[Bdc101]

Here is the other thread I referenced which has the exact same problem. Quite recent



Https://xoutpost.com/bmw-sav-forums/...n-problem.html

[upallnight]

Post #15 is my post that the fan may be good, but you get a bad fan fault if the fan doesn't spin to send back a voltage signal to the DME.

[andrewwynn]

I would provide an alternative 12v path to that main fan supply (thru a fuse) and see if you get the fan to spin.

One thing that confused me: you said you had 12v "on both sides of the fuse".

Confirm you means from each side to ground, 12v across the fuse is how you tell a fuse is blown.

[Clavurion]

Originally Posted by andrewwynn

One thing that confused me: you said you had 12v "on both sides of the fuse".

Confirm you means from each side to ground, 12v across the fuse is how you tell a fuse is blown.

Same thing made me wonder.

[80stech]

I think you need to look at a 2002 wiring diagram to see if it matches what you have. What are you using for ground when you check at the fan connector ?? Are you using a test light or multimeter?

[wpoll]

These two diagrams indicate the aux fan gets power from fuse is F107 via X1982...

https://www.newtis.info/tisv2/a/en/e...7-fuse/uPpddMO

https://www.newtis.info/tisv2/a/en/e...ic-fan/uVU0vrf

[Clavurion]

Originally Posted by wpoll

These two diagrams indicate the aux fan gets power from fuse is F107 via X1982...

https://www.newtis.info/tisv2/a/en/e...7-fuse/uPpddMO

https://www.newtis.info/tisv2/a/en/e...ic-fan/uVU0vrf

Aren't those diagrams for facelift and the thread started has pre-facelift? I faintly remember checking those diagrams during the earlier thread regarding the same problem.

https://www.newtis.info/tisv2/a/en/e.../electric-fan/

Facelift would have the big main fuses behind fusebox.

[Bdc101]

I meant that I measure 12 volts to ground from both sides of the fuse -- confirming that it is not blown or otherwise faulty.



My car is indeed a pre-facelift (production 11/2002). But because it was easy to check, I went and checked fuse F107 anyways and ... DING DING DING!


Fuse F107 has continuity to big red/blue wire at the fan connector -- the one that is supposed to have constant 12v.



I checked fuse F107 and it is bad. There was 12v on the bus side, and 0v on the downstream end. I removed the fuse and I haven't used this kind before; it is not immediately obvious whether it's blown or not. But the DMM says it has very high resistance. So newtis and my Bentley manual are wrong!



I am piecing the puzzle together here. I did find a part of that wire near the connector which had been shaved, probably from getting whacked by the engine bay fan. I realized during this troubleshooting process that that wire has 12 volts all the time, even when the key is out. It must have just brushed the chassis and shorted, and blown the fuse, and since we all thought the fuse was F61 like the manual says, we stopped there. But the wiring diagram was wrong the whole time! I wonder if the other poster (daveking) has the same problem.



My gut was telling me there was no way a #6 wire could have broken without shorting out somewhere, or having an intermittent connection.



Thank you all for your help! And especially wpoll, for finding the wrong wiring diagram that turned out to be right!