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Old 05-07-2013, 12:54 PM   #1
Edm Rex
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Electric Fan still won't work

My 323i with manual transmission overheated last week, radiator seemed to be leaking. Replaced the radiator along with the whole cooling system and its still getting hot, as the fan isn't turning on. Replaced the fan with a brand new Chinese one, nothing changed. Today I installed a working Bosch fan and still it does not engage. I disconnected the sensor from the lower radiator hose to engage the fan but nothing happens. The fan still doesn't turn on. I believe that this leaves me to an electrical problem. I am getting 12V to the big connector that plugs in to the fan. How do I narrow down the problem, what could possibly be wrong at this point?

EDIT: I am getting a good ground and power to the fan plug. I've tried 2 different fans and the fans still do not come on. What's the likelihood of a bad ecu? What else could be wrong?

Last edited by Edm Rex; 05-28-2013 at 08:47 PM.
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Old 05-07-2013, 01:01 PM   #2
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Theoretically you can drive back home without a fan, as long as you are moving air will go through the rad. Just avoid any traffic. Stop and go will make you overheat. And don't use the AC so that you don't put any more strain on your cooling system.

If you have an advanced diagnostic tool like snap-on or INPA you can manually force the fan to come on just to make sure it works.
Is you new fan Brand New? Does the wiring look OK? do you have any codes thrown? a non functioning fan will throw a code but won't trigger the check engine light.
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Old 05-07-2013, 01:50 PM   #3
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The red/blue thick wire in the wiring harness on the fan shroud has constant 12v in it, maybe you can hook that up to the fan motor.
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Old 05-07-2013, 03:13 PM   #4
Edm Rex
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Originally Posted by El Polo View Post
Theoretically you can drive back home without a fan, as long as you are moving air will go through the rad. Just avoid any traffic. Stop and go will make you overheat. And don't use the AC so that you don't put any more strain on your cooling system.

If you have an advanced diagnostic tool like snap-on or INPA you can manually force the fan to come on just to make sure it works.
Is you new fan Brand New? Does the wiring look OK? do you have any codes thrown? a non functioning fan will throw a code but won't trigger the check engine light.
The fan is brand new. The plug that connects to the fan looks okay. I don't have a check engine light but I have not checked for codes as I don't have a diagnostic tool
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Old 05-07-2013, 03:22 PM   #5
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The red/blue thick wire in the wiring harness on the fan shroud has constant 12v in it, maybe you can hook that up to the fan motor.
Check for 12v in this connector. Bypassing it is not a bad idea so you can drive without overheating in the meantime - it'll run all the time while the key is on, but shouldn't cause a problem until you get it figured out and can remove the bypass.
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Old 05-07-2013, 03:43 PM   #6
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Check for 12v in this connector. Bypassing it is not a bad idea so you can drive without overheating in the meantime - it'll run all the time while the key is on, but shouldn't cause a problem until you get it figured out and can remove the bypass.
I'll check it later today. How exactly would I bypass it to make my fan run when the car is on?
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Old 05-07-2013, 07:48 PM   #7
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Unfortunately you cannot bypass the fan as it is computer controlled and the controller within the fan itself must be triggered by the ECU. The fan is controlled by a PWM signal from the ECU. So it always has 12V, even when the ignition is off, and only comes on when the ECU sends a PWM signal to the fan controller. The first question I would have is on the new fan. Where did you buy it and was it a specific puller fan for a manual trans. It must have the controller built in. You can search this site for other threads regarding issues with Siemans fans. I had the same issue and bought an OEM Bosch fan from Pelican and the problem was solved.
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Old 05-07-2013, 10:15 PM   #8
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Unfortunately you cannot bypass the fan as it is computer controlled and the controller within the fan itself must be triggered by the ECU. The fan is controlled by a PWM signal from the ECU. So it always has 12V, even when the ignition is off, and only comes on when the ECU sends a PWM signal to the fan controller. The first question I would have is on the new fan. Where did you buy it and was it a specific puller fan for a manual trans. It must have the controller built in. You can search this site for other threads regarding issues with Siemans fans. I had the same issue and bought an OEM Bosch fan from Pelican and the problem was solved.
The fan is for the manual transmission and it's the same as the oem one, except its a chinese brand. I'll be putting in a bosch oem unit later, I just need to get the car on the road to get home where I can pin point the issue. There isn't a way of hooking up the fan so it's constantly running?
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Old 05-08-2013, 02:01 AM   #9
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The fan is for the manual transmission and it's the same as the oem one, except its a chinese brand.
I'm pretty sure you just diagnosed your problem.
This does not help you get home, but it does explain your current issue.
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Old 05-08-2013, 06:39 AM   #10
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Apply 12v directly to the motor of the fan... if it actually works. Bypass the fans own control unit.
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Old 05-14-2013, 07:03 PM   #11
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I'm pretty sure you just diagnosed your problem.
This does not help you get home, but it does explain your current issue.

I drove for 200 miles without overheating as it was mostly highway. I checked the voltage at the thick brown wire that connects to the fan and it's getting 12V when the car is off. So the fan is getting power. Does that mean the fan itself is the only thing that could be wrong? What about a fuse or anything else? The fan itself is brand new but its a chinese brand
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Old 05-15-2013, 12:50 PM   #12
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I'm having the same problem with my fan not turning on. No codes or check engine light though. I've been told that it is the fan, or probably the controller that is built into it, and that I need to replace the whole assembly.

Did you install a Bosch fan? Did it fix the problem?

Also, my A/C doesn't seem to get cold either, I wonder if the engineers at BMW have made it so the A/C won't work if your fan goes bad...
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Old 05-15-2013, 01:50 PM   #13
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Also, my A/C doesn't seem to get cold either, I wonder if the engineers at BMW have made it so the A/C won't work if your fan goes bad...
That is likely since the fan turns on when the AC is on.
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"Would the codes indicate if it's the carburator?"
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Old 05-15-2013, 01:54 PM   #14
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I drove for 200 miles without overheating as it was mostly highway. I checked the voltage at the thick brown wire that connects to the fan and it's getting 12V when the car is off. So the fan is getting power. Does that mean the fan itself is the only thing that could be wrong? What about a fuse or anything else? The fan itself is brand new but its a chinese brand
I am pretty sure the fan works, a cheap brand may not last as long though.
The ECM receives input from different sources to turn on the fan. Coolant temperature, AC pressure, vehicle speed and more. You need to troubleshoot each of those sources. Do you have a wiring diagram to work with?
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"Would the codes indicate if it's the carburator?"
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Old 05-15-2013, 01:55 PM   #15
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Originally Posted by Rotten Robbie View Post
I'm having the same problem with my fan not turning on. No codes or check engine light though. I've been told that it is the fan, or probably the controller that is built into it, and that I need to replace the whole assembly.

Did you install a Bosch fan? Did it fix the problem?

Also, my A/C doesn't seem to get cold either, I wonder if the engineers at BMW have made it so the A/C won't work if your fan goes bad...
The engineers at BMW did not make it that way, that is just how AC systems work. The fan has to dissipate excess heat, in order for the system to function.
All cars behave the same way, if the fan stops working, not just BMW's.

Also, you most likely will not get a code for a non-functioning fan. You should, since it is a fairly critical item, but it does not throw a code.

I just bought a new Bosch fan assembly from BMA Parts last week, for about $175 shipped. Use the coupon code "SpecE30" to get a 5% discount. It is about $185 without the discount. You won't find a Bosch fan for less anywhere else, I don't think.

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Old 05-15-2013, 02:06 PM   #16
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I drove for 200 miles without overheating as it was mostly highway. I checked the voltage at the thick brown wire that connects to the fan and it's getting 12V when the car is off. So the fan is getting power. Does that mean the fan itself is the only thing that could be wrong? What about a fuse or anything else? The fan itself is brand new but its a chinese brand
If you are getting 12V at the fan, then you definitely don't have a bad fuse. It may possibly be a bad fan relay, but I would think that would prevent you from reading 12V at the fan as well. You could try swapping that out though.
Most likely it is the controller on the fan housing that is bad. I would get rid of that Chinese fan. How much did you pay for it?
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Old 05-16-2013, 02:30 AM   #17
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If you are getting 12V at the fan, then you definitely don't have a bad fuse. It may possibly be a bad fan relay, but I would think that would prevent you from reading 12V at the fan as well. You could try swapping that out though.
Most likely it is the controller on the fan housing that is bad. I would get rid of that Chinese fan. How much did you pay for it?
The chinese fan is getting returned,I only bought it as it had overnight shipping available and I needed to get it home. So if I have 12V at the brown wire that connects to the fan, it means that the fan is getting power?
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Old 05-16-2013, 06:00 AM   #18
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Did you replace your temp sensor on the lower radiator hose?

...and I skimmed the thread...are you sure you bled the system correctly? I ask, because honestly, I can't remember the last time my fan came on...although, summer is on the way, so I'm sure it will eventually!

Have you tried putting on your AC? The fan, I'm almost positive, is supposed to kick on momentarily when you do, just so the car knows it's there if you need it.

hth
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Old 05-16-2013, 11:17 AM   #19
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Did you replace your temp sensor on the lower radiator hose?

...and I skimmed the thread...are you sure you bled the system correctly? I ask, because honestly, I can't remember the last time my fan came on...although, summer is on the way, so I'm sure it will eventually!

Have you tried putting on your AC? The fan, I'm almost positive, is supposed to kick on momentarily when you do, just so the car knows it's there if you need it.

hth
My AC never worked since I've owned the car, and the temp sensor was replaced along with the whole cooling system about half a year ago. I even disconnected the temp sensor which should make the fan turn on but it doesn't. I've bled the system many many times.
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Old 05-17-2013, 01:10 PM   #20
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My fan never turns on either...

I'm trying to figure out why my fan won't turn on. I have a 01 325 w manual and it just has one electric fan. I have 12V to the big plug all the time, but the fan never turns on... I think it is the fan or rather the integrated speed control moudle on it, but I don't want to make a $300 guess. If I unplug the sensor in the lower rad hose -still nothing. Any ideas? Is the little box in my picture the control module?
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