Hi, Afew years ago the E39 went through a recall on the aux cooling fans.do you no if yours was done.?
Ok the three wire are two big wires 12v and earth and the 0.5 wire is the activation wire from the DME,this is a pulse width modulated signal, which means the more volts sent down the wire the faster the fan will turn.
Please check when the fan is plugged in there should be battery voltage on the 0.5 wire and when unplugged there should be about 4-6 volts just with the key in postion two..
Yes there is battery voltage as suggested, does this mean the fan is ok and somthing else is wrong?
do you mean 4-6 volts on the thin wire from the main loom with respect to ov with the fan unplugged?
Hi I have just been and checked the plug with the fan unplugged - there is no voltage present on the cable (yellow/red) - doe this help?
Hi, yes key in position two.
I am an electrical engineer and have a multi meter to check, will let you know the result tomorrow, it is 2100 and raining here (North Wales - the wettest part of the UK).
I guess that if i test the wire coming from the ecu, I should see 4-6 V present. You mentioned PWM do you know the size (voltage) of the pulse, is it a pulse with respect to 12V or zero V and frequency so I can set up a rig to test the fan?
I have looked in the ebox before - there are two large ecu's present fixed in the middle of the ebox, is the DME the front one?
once again many thanks.
Yes you should see 4-6 volts from the DME,It is a square wave signel if you can scope the wire.
The best thing to do first is do a wire test from DME to aux fan plug to check for brakes,You will have to look for the same wire colour and size,there might be a few just test for resistance.
Not sure which control unit it will be,normally the one with more plugs.The other one is hopefully The EGS for auto box..
Where to start?
2 wire breaks in the thin yellow/red cable - 1 in the ebox and 1 four inches from the fan plug.
Inside the fan motor - after dissassembly I found that three of the winding connections were corroded. After cleaning and re assembly I applied 12 volts to the motor and connected a function generator to the signal reference cable. After selecting a square wave at 6 volts I increased the frequency to about 150Hz at which the motor kicked into life (tried this before disassembly with no results).
The signal from the DME with the key in position 2 is about 2mVDC (scoped measurement), however the signal cable from the fan when disconnected has 12V present. When connected to the DME a pulse wave appeared and the motor started. It looks like the motor supplies the DME fan control circuit with its power supply.
Anyway all repaired now and working.
Many thanks again
Thats good paul hope every thing is ok now..
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Once again thanks for your help