Hot wires tend to suggest circuit overload. Have you checked the current draw? I don't know what it should be.look it up. Put an ammeter in series with fan and the connector. You may have a short to ground somewhere. There are 3 wires. Brown goes to ground. The smaller green/black one (?) is the signal wire from the DME to the fan that controls the speed. You could check the continuity on that cable from the fan harness connector to the DME. It goes to pin 4 on connector X60004 of the MS43 DME.The 40 pin connector 2nd from the right.


Google "e46 electric fan not working".some good vids on the net.

 

Probably should clarify, when I say hot, I mean that there’s a positive polarity, not hot to touch.

 

All electric cooling fans in the E46 have power and ground at all times. The operation of the efan is controlled by the engine computer (DME). The third small wire in the efan connector is connected to the DME. The DME controls the efan via pulse wave modulation (PWM). Basically, PWM is square wave signal whereby the efan is turned on when the PWM is “high” and it’s off when the PWM is “low.” To increase the efan’s speed the DME sends a PWM signals with longer (in time) “highs” and shorter (in time) “lows.” The efan has a controller that uses the PWM signals to turn the voltage on and off.

 

There's 3 wires to the fan controller.

Big power & ground. Then there's a small wire from the DME pin #4. That sends a varying square wave signal to the controller to ramp up/down the fan speed.

 

I see your forum name is Marks E36. Are we talking about a E36 or 46?
Year/model please...

 

1999 E46 ( My son’s project car)

 

Read this:

• Electric Fan Guide

 

I understand the power inputs to the fan control module- power, ground and the other wire from the DME. It’s the output that doesn’t make sense. Does the module somehow change the polarity of one of the wires to create a circuit? I wouldn’t have thought so. All wiring diagrams I have on the system indicate the wire colors entering the FCM but not the wires exiting. All I’m simply trying to do is manually jump the wires to test the fan motor as it’s never operating and the car overheats. The confusing part is both wires connected to the actual motor are carrying positive polarity when the ignition is switched on. The FCM itself is attached to a plastic fan shroud, I can’t see anywhere else where the fan motor connects to ground. All I’m trying to achieve is to apply a simple jump to the fan motor to see if it works, so if anyone knows what wire does what on the actual motor itself that would be extremely helpful. Thank you everyone for your input.

 

The E46 Fan motor is variable speed. The DME sends the fan controller a Pulsed Square Wave (PSW) to tell it what speed to turn the fan. The fan controller simply amplifies this signal and sends it to the fan motor.

Connect to the fan control output or the 2 leads that connect to the fan. Flick your multi-meter to AC Volts and see what sort of voltage you are getting. With INPA, set the speed of the fan and see if the AC Volts change. Test at 25%, 50%, 75% and 100% speed. The actual value of AC Volts is not important, it's the way that it changes that is important. The AC Volts should reduce as the fan speed increases. This is because the fan supply at low speed looks like a square wave AC supply but as the fan speed increases, it looks more like a DC supply.

 

You can connect 12V and ground to the fan motor to test it for spinning. They are very robust.
The FCM, a current amplifier similar to a light dimmer, is nearly always the part that fails.
Go hit the link I posted back in post #8 and read that document.

 

BallDawg, thankyou, that link was outstanding. I don’t have INPA, or anything similar. At the end of the day, based on this picture I borrowed from your link, which of these wires are 12v and ground, just so I know how to connect them to test the motor as I have 12 volts positive current in both (test lamp lights) when the other end of a test lamp is connected to ground. Appreciate your help, just trying to figure out if I need to replace the FCM or the entire assembly.

 

You can ONLY replace the entire assembly as the FCM is not sold separately.
The electric fan unit is less than $100 on ebay. They are all chinesium these days, so pick one.

 

If you get lucky, you can find a stock one in a salvage yard. I got one for about $25. Maybe get two, in case one of them takes a dump.

 

Thanks everyone, appreciate your help.

 

Cooling fan not working at all, there is both power at the high and low sides of the fan control module as well as good ground.

This statement needs more clarify. Power at the high and low sides of the fan controller as well as good ground; do you mean there are 3 heavy wires? It should only have 2 heavy wires (one for 12v and the other is ground) and the 3rd small PWM signal wire.

The two wires that exit the module direct to the fan motor are BOTH HOT!!!

When the fan not running or off, these two wires must have the same 12v (as you said both hot) for a zero potential difference or zero current to the motor.
The way it works: one wire is constant 12v, and the other wire is also 12v when fan off, or it is at 90% active low duty cycle for max speed (when the small signal wire has 90% duty cycle active high), or any duty cycle in between from 90% to 10% (or maybe between 80% and 20% as I don't remember).
90% active low means 10% of the time at 12v and 90% of the time at 0V.

You can unplug the cable at the lower hose sensor to force the DME to run the fan at max speed.