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      10-21-2024, 05:23 PM   #1
bmwH99
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Question BMW X3 F25 Aux Fan Issue

After a few projects I noticed my X3 radiator fan isnt turning on at all.

The main indicator of this was the AC not working and blowing hot air on a hour long drive.

My initial thought was that the fan motor might have burnt out - I pulled two off junk yard cars and one from ebay : they all had the same result as my original one. When I plugged them in they would turn on briefly then shut off.

I then replaced the fan relay and coolant temp sensor : same issue.

I then checked all the fuses in both fuse boxes and the IVM with a multi meter : all fuses checked out

I then unplugged the coolant temperature wire from the sensor and the motor began running.

I checked the coolant temperature wire and it checked out with one prong sending 5v and the other -5v.
I also checked the Aux Fan power cable when the sensor was in and out.
Car was sending almost double the power when the sensor was unplugged.

At this point I am lost at what i should be looking at for the culprit. I noticed the coolant temp sensor wires lead to the back right of the engine where many wires come in. The only possible lead i have now is that when I was pulling the old charge pipe I might have striped a wire and grounded it or pulled one, but from the looks of it they all seem to be seated properly.

Recent work done: head cover gasket, oil filter housing gasket, charge pipe, transmission filter, coolant pump

Thanks for the read fellas please lmk if you've dealt with something similar and what was your fix
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      10-21-2024, 06:20 PM   #2
Hellshalfacre
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Quote:
Originally Posted by bmwH99 View Post
After a few projects I noticed my X3 radiator fan isnt turning on at all.

The main indicator of this was the AC not working and blowing hot air on a hour long drive.

My initial thought was that the fan motor might have burnt out - I pulled two off junk yard cars and one from ebay : they all had the same result as my original one. When I plugged them in they would turn on briefly then shut off.

I then replaced the fan relay and coolant temp sensor : same issue.

I then checked all the fuses in both fuse boxes and the IVM with a multi meter : all fuses checked out

I then unplugged the coolant temperature wire from the sensor and the motor began running.

I checked the coolant temperature wire and it checked out with one prong sending 5v and the other -5v.
I also checked the Aux Fan power cable when the sensor was in and out.
Car was sending almost double the power when the sensor was unplugged.

At this point I am lost at what i should be looking at for the culprit. I noticed the coolant temp sensor wires lead to the back right of the engine where many wires come in. The only possible lead i have now is that when I was pulling the old charge pipe I might have striped a wire and grounded it or pulled one, but from the looks of it they all seem to be seated properly.

Recent work done: head cover gasket, oil filter housing gasket, charge pipe, transmission filter, coolant pump

Thanks for the read fellas please lmk if you've dealt with something similar and what was your fix
Hello. Your ac blowing hot while on the road has nothing to do with your fan. If it was only blowing warm when the car was stopped, but then started to cool when moving, that would be an indication that the aux fan was bad. Your fan likely isn't turning on because your ac compressor isn't turning on.
Confirm that your ac clutch wire wasn't disconnected during your work, the clutch is engaged when you turn ac on (not just the pulley turning) and report your high and low side pressures when the ac is on.
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