AC Fan Trigger Wire

[X5-D-Sport]

AC Fan Trigger Wire...

Is this thin wire feeding a simple voltage to the fan to trigger the fan ?
or
Is it a modulated Pulsed Signal ??

My AC front Rad Fan has never worked, and before I fry it putting a 12 volt feed to it, I want to know if it is triggered with a signal or a simple voltage..

Any one know the answer ?


If it is a simple forward voltage, I can tap this from the snow-flake switch LED via a tiny relay to pop a voltage to the fan motor & set it in motion.... if not, then I have to find whatever it is that sets the signal & replace it.
I have power getting to the fan, just no trigger signal/voltage....

I have connected several fan units to my vehicle & none work.... even one still in another vehicle that is seen working minutes before & after....

Some how mine simply won't work..... (or the fan lol  ) :blink:)

[X5-D-Sport]

Update,

I stripped the 2nd fan motor apart I bought off flea-bay...
the fan motor is a variable speed DC brushless motor... with a load of waterproofed processors & gubbins sat in there it appears...

The trigger wire could still be either a signal or a varying voltage...

[X5Sport]

Any way you can check via a 'working' car?

I know the lighting system uses a PWM coded signal to reduce the brightness of the sidelights  It might also be the system for the fan?

[X5-D-Sport]

Re PWM - Pulse Width Modulation...

In theory, when the Positive edges of the pulsed a maximum rate it ceases to become a pulse, but instead a constant voltage where there are no spaces between wave forms.... there-by a + volt imitation....
So, potentially, to get the fan to run at max speed, a solid voltage could be applied....

I will borrow an oscilloscope and see what my friends cars' signal out put is... may help, especially if I can rig the fan to simply come on full belt when the snow-flake is pressed...

[X5Sport]

And who said engineering isn't fun..... )

Just be glad it might only be simple PWM as you guessed.  Some of the techniques we use in telecoms are mind boggling (read as need specialised and very expensive equipment) to measure!!

[X5-D-Sport]

Engineering & Fun..... agreed.... but um pulling out the last few sparse tufts of my remaining hair... in frustration trying to get this AC fan going.
The fan is fine.... its the 2 1/4 tons of junk its plugged into that wont work lol  )

My head is some what resembling a waterlogged swamp... with odd grassy bits poking thru the stagnant water...

[Horizon]

https://enderw88.wordpress.com/2012/05/ ... ng-relays/

Found this after a Google search, could the E53 be wired similarly to this?

http://www.xoutpost.com/bmw-sav-forums/ ... oning.html
Try this, very long post . Explains wiring and signals etc eventually

[X5-D-Sport]

I Horizon,

I read thru both posts, and they throw up 3 potential parts failures in addition to the possible faulty control panel above the centre console.

Potentially, there may be a relay fault in the rear right boot cubby, and / or a sensor box mounted on the top of the radiator - & this sensor does not appear to having anything to do with the thin trigger wire hat goes to the fan...

Any thoughts ??

[X5Sport]

I thought that sensor was the 'pong' detector that switches the airflow into recirc if it detects fumes - such as when stuck in traffic in a tunnel - not after a curry night :puke: :hypo: