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aux fan not starting with ac

2K views 13 replies 4 participants last post by  cowartdo 
#1 ·
my 2006 x5 3.0 ac takes several minutes to work. It comes on when the aux fan reaches the normal engine temp. Then it is normal. I've seen several post with problem but not clear on the exact cause and solution.
 
#2 ·
The m54 engine uses a variable speed aux fan which does NOT come on every time the AC button is pressed like in older BMWs with the 2 & 3 speed aux fans.

Your aux fan is controlled by the DME/ECU and sends a PWM signal to a final output stage on the aux fan when certain criteria is met:

 
#4 ·
Finally found that my problem is an unresolved issue BMW knows about. I have been perplexed by the number of threads with this problem, but all the testing is not going to resolve this one. This will not be resolved until a critical mass of owners call BMW America customer service and get a solution. I just don't think they put a lot of resource into a 7 plus year old problem. Soooo..... you can evidently stop replacing fans and probing the ECM. Sorry to find this out. But they said "they are working on it."
 
#6 ·
I am not sure that will resolve the problem. If you do it, let me know. But my technical guy said the best thing is to call BMW north america and hopefully they will come up with a solution. Many people have it. I hate to spend a lot on brainstorming a problem with no solution. Thanks
 
#7 ·
Auxiliary fan not running

Hello everyone,

I can't recall hearing the auxiliary fan on my '06 E53 engage in a long time, and during a recent heatwave with the AC running, the engine temperature was a bit hotter than normal. I understand that this is a common problem, and it's also tricky because this fan only engages under certain conditions. Now I'm trying to figure out whether its likely to be the fan motor or not.

The blades spin freely, and **sometimes** if the "max ac" button is pressed, the fan will turn for a few inches, then stop, so the motor is not 100% non-functioning. If it were truly the fan motor, I would not expect this behavior - is this more likely the second stage or the sensor? Would a fan unit with a bad motor be able to power up briefly as described?

Many thanks for any opinions on this.
 
#8 ·
any replies appreciated.

I have exactly the same issue. with ac on max the aux fan motor will go forwards maybe an inch and then backwards maybe an inch then stop. I am under the same impression - if the fan motor was dead then it would not move at all?

I have had the compressor hot wired and it works fine, the clutch engages and blows ice cold air in the car. I have had the system regassed too so I know the pressure is good.

I have 12v on the fan but no square wave signal to drive the fan?

where do I need to look next?
 
#9 ·
That is interesting to have the compressor hotwired. There is a sensor on the ac line. On my vehicle, if you unplug the sensor, the fan turns on. The fan has, I think, two speeds. One for the ac unit(if working properly) and normal operating temperature mode. The higher speed is in hotter conditions like stop and go traffic. It looked like when I disconnected the sensor, the fan came on, but the compressor stopped. I don't think BMW is focused on this since the vehicles are older and people have the impression the fan is going bad. BMW probably wants people to replace the expensive fan first so if they have to do a recall, it won't be a total loss.
 
#12 ·
If BMW tech people monitor this, they could give us a update on their efforts to find the ghost in the machine. I am afraid that if it was that simple, it would be resolved, but it must be 1) not reached the threshold to give serious thought and effort or 2) they solved it and it cost a boatload to fix. I cant fathom this company could not find why the fan does not come on.
 
#14 ·
ac

I think the trigger for the fan(aside from the temp) is the pressure in the ac line. I added a bit of R134 to increase the pressure and I think the lag time was reduced. That being said, I was scared to add too much and damage the system. I think I will get use to a 5 minute delay...
 
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