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There is no easy way to tell, if you put direct power to the terminals, they will not power the fan, as it needs the signal from the small wire (small wire is the one that controls the speed of the fan, it basically takes a signal from the ECU)
what i did is that i deciphered the ECU terminal number, then got a volt metere to measure resistance in the wire (the small wire) from the ECU to the Fan plug (just to see if the resistance is high, which means that there is in fact a disruption), i found the resistance to be high, so i decided to just introduce a new wire (i cut the old wire from both ends, and plugged it, just in case...) and then routed the new wire from the ECU to the fan plug, it worked. i hope that this helps you resolve your issue.
 

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There is no easy way to tell, if you put direct power to the terminals, they will not power the fan, as it needs the signal from the small wire (small wire is the one that controls the speed of the fan, it basically takes a signal from the ECU)
what i did is that i deciphered the ECU terminal number, then got a volt metere to measure resistance in the wire (the small wire) from the ECU to the Fan plug (just to see if the resistance is high, which means that there is in fact a disruption), i found the resistance to be high, so i decided to just introduce a new wire (i cut the old wire from both ends, and plugged it, just in case...) and then routed the new wire from the ECU to the fan plug, it worked. i hope that this helps you resolve your issue.
ill try the same, i will wire a new cable from ecu to the fan to see if that work, is it the same pin 4?
 

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can some one point me in the right direction, of witch plug and ping # in the ECU is the fan radiator signal? or a picture of the plug, i did find a website bmwtis but the charge 30 for 24 hours to show diagram, thats just crazy
 

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have a 318i N42 engine (from the Philippines but similar to the euro version). Forgive the info overload, as I just wanted to provide as much info to all of you.

The car has an electric fan on the engine side of the radiator (and no, I don't have a viscuous fan). It has the resistor(?) block at the top of the housing. I have a coolant temp outlet sensor on the lower rad hose.

I first noticed a problem with the cooling system when I drove 3kms, idled for 15 mins but the A/C was not doing its thing and I thought it might just be the tropical weather. When I started driving again, the temp gauge went over the halfway mark so I immediately turned off the engine. I popped off the hood, turned the engine on again to see if the fan would turn on but there's nothing so I just waited for it to cool. I drove home after 30 minutes without the A/C, and monitoring my temperature through a bluetooth OBDII. Everything's OK, but within a couple of blocks from home I wanted to see if it would overheat again, and sure enough, it started climbing to 105C, from which I reached home and checked again if the fan would start, but sure enough, it's not turning on.

I did these troubleshooting steps so far:
1. 50 amp fuse OK
2. Scanned using PA Soft 1.4 for errors, none of which are in the DME, or anything related to the cooling system
3. Tried turning the fan on by using INPA e-Blower Activate to no avail
4. Scanned for temp using INPA
  • Coolant Temp is 95C after 15mins of idle
  • Coolant Outlet Temp is at 60C+
  • Tried turning on the AC again, sure enough it went to 103C+ only after a few minutes
  • Turned off the car
5. Tried removing the coolant temp outlet connector, and turned it on again hoping the default values would force the fan to turn on, but still a no go
6. Checked the big plug of the fan for voltage, from which I'm reading 12V on the red wire. I know that the thin green wire goes to the ECU and there's no easy way to test it so I haven't done it yet.

I also tried to check the voltage on the plug for the resistor(?) block, but unfortunately my probe wouldn't fit. I tried using a random wire to insert to the plug and my probe but it won't read anything (I'm not so good with electrical troubleshooting).

Prior to this, there's no strange noise from the engine bay so I assume the mechanical part of the fan is still OK, unless something got fried inside that I cannot simply check. Another idea I have - is there a carbon on the electric fan? It's quite easy to replace the carbon if it just simply ran out, but I don't think that's the issue as the fan is just dead, and based on my other cars, if it's a carbon issue, the fan would "slowly" die, instead of just being totally dead.

So my question is, should I start splicing the wires going to the resistor(?) block and checking it with the corresponding connection on the relay box? This is my last resort as I don't want to cut open anything necessary. If this is my next step, how do I properly do this? Or should I test something else? Or is it a definite electric fan problem and I should just straight up replace it?

The electric fan has been replaced roughly 5 years ago (drove 15 thousand kilometers since), but is not an OEM fan, as the original costs $300 around here (vs. $200). So yeah, I wish I added a $100 back then, but I was doing a whole cooling system refresh and I figured meh, it's just a fan with a motor, so I put all my $ on going OEM to all other parts (ie. hoses, thermostat, sensors, etc).
 

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Remove the plug and supply it with 12 volts directly. The fan should leave the room immediately. This will let you know whether or not the motor is operational.
 
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