[Ethird]

Hi All - the vehicle in question is an E70 X5, but since they share a very similar engine management scheme, I wanted to see if any of you N52 experts have encountered a similar problem.

My car never turns on the radiator cooling fan - not when you first start the car, and not even sitting in traffic. The fan and relay are both good, plus I've got 12V, a good ground and a 100Hz signal at the fan, and if I pull the coolant temp sensor wire while the engine's running, the car immediately fires the fan up to full speed and sets the SES light with a coolant temp sensor code.

The weird thing is, the car never approaches an overheat. Today in 90F ambient temps, I drove around in traffic and it operated exactly at it's supposed to - I was seeing 108C when taking it easy and idling ("Eco" mode), 102C when driving ("Normal" mode) and occasionally it would drop to 96C ("High" mode). It's doing all of this just with the variable-pressure water pump - it never kicks on the fan even when I've got the temp up and I'm stopped in traffic.

Perhaps an important note is that the A/C has been inop for about a year. Could it be that the car doesn't need to turn on the fan when the A/C is out of the picture, so it doesn't bother? (this doesn't seem likely to me)

Mainly, I just have concern that the fan will never turn on, even if the water pump starts to fail and it runs up to the 120C threshold where it starts turning things off. The car is obviously doing ok for now, but I don't want to get 300 miles from home on a road trip and have the thing start cooking itself because the fan isn't operating under the correct parameters.

[kkasson]

Do you have a scanner that will read BMW-specific codes? If so and there are no codes then I wouldn't worry about it. If it runs when you disconnect the sensor then everything should be working and it should be able to turn it on if it needs it.

If you really wanted to be safe, if you're able to reach it maybe you could unplug the water pump and start the engine. The fan should turn on immediately, I believe.

[terryd5150]

I have AC issues, too. Because of this, I don't run the AC (yes, it sucks).

My fan doesn't come on either; however, I don't drive the car very far (because having no AC sucks).

The most I usually drive it is 10 miles one-way at highway speeds.

When I pull up to the toll booths the fan is not on.

When I make to back into my garage, the fan is still not on, even though the car is up to operating temperature.

In all scenarios, the fan immediately comes on when I turn the AC on (even though the AC only blows hot air).

[BB_cuda]

I'm right there with last guy [post #3]. My A/C does work though.

My car is a 2011 335d (M57 engine). The coolant gets up to 93C and fan will not activate. 93C happens if sat parked.If i turn on A/C, fan immediately comes on and running at high speed. If i drive, the temp falls to about 85C. My thermostat was changed about 3 years ago and driven 19,000 miles since. A friend has suggested i change the relay that is located very close to the power steering reservoir.

Don't know if there is a temperature sending unit that might have gone bad. The temperatures i'm quoting are from the hidden menus within the cluster that I unlocked. thanks

[WhoGotTheKeys?]

Hey guys - I know this post is quite old now, but I'm wondering if any of you are still around posting and can answer some questions. Were any of you able to solve the mystery of the cooling fan not turning on?

I am also experiencing no fan action. I replaced the coolant temperature sensor and still have had no luck. When I unplug the sensor and start her up, the fan blows on high speed.

I have displayed the coolant temperature from the hidden menu and see the same temperature fluctuations as Ethird [Post #1] while driving, from thermostat and water pump action.

My A/C is also not functioning. In fact, the clutch plate on my compressor seems to be constantly engaged. Pressing the snowflake button does result in light up but the fan does not switch on. I am having my A/C system looked at by a trusted mechanic in a few days.

In any of your cases, did repairing the A/C system allow the fan to return to normal function again? I am wondering if the pressure of the A/C system via the A/C pressure sensor play a part in the ECU calculations?

Thanks a bunch for any help you can provide!

[e90yyc]

Originally Posted by WhoGotTheKeys?

Hey guys - I know this post is quite old now, but I'm wondering if any of you are still around posting and can answer some questions. Were any of you able to solve the mystery of the cooling fan not turning on?

I am also experiencing no fan action. I replaced the coolant temperature sensor and still have had no luck. When I unplug the sensor and start her up, the fan blows on high speed.

I have displayed the coolant temperature from the hidden menu and see the same temperature fluctuations as Ethird [Post #1] while driving, from thermostat and water pump action.

My A/C is also not functioning. In fact, the clutch plate on my compressor seems to be constantly engaged. Pressing the snowflake button does result in light up but the fan does not switch on. I am having my A/C system looked at by a trusted mechanic in a few days.

In any of your cases, did repairing the A/C system allow the fan to return to normal function again? I am wondering if the pressure of the A/C system via the A/C pressure sensor play a part in the ECU calculations?

Thanks a bunch for any help you can provide!

I know this is very much secondary to your main question, but regarding the AC system:

There is no clutch. These are variable displacement compressors, so the driveshaft of the unit is constantly spinning. The stroke of the pistons is determined by the angle of the wobble plate, which is determined by the car based on AC activation and load on the system.

It’s kind of cool. Google “variable displacement compressor” and check it out. The reason I’m telling you this is because you won’t feel the same kick or hear the same sound you’d hear in a vehicle with a clutch-based AC compressor. Further, it’s worth checking refrigerant pressures before looking too deep. Perhaps a simple recharge is all that’s needed for that issue, though obviously you may still have a leak. The evaporators on these cars are known to leak, and even for a seasoned DIY’er it’s literally an all-weekend job. You have to tear so much shit off just to access it. I’m sure your mechanic can diagnose it.

Hopefully someone else can chime in and help you get to the root of the actual issue.

[WhoGotTheKeys?]

Originally Posted by e90yyc

I know this is very much secondary to your main question, but regarding the AC system:

There is no clutch. These are variable displacement compressors, so the driveshaft of the unit is constantly spinning. The stroke of the pistons is determined by the angle of the wobble plate, which is determined by the car based on AC activation and load on the system.

It’s kind of cool. Google “variable displacement compressor” and check it out. The reason I’m telling you this is because you won’t feel the same kick or hear the same sound you’d hear in a vehicle with a clutch-based AC compressor. Further, it’s worth checking refrigerant pressures before looking too deep. Perhaps a simple recharge is all that’s needed for that issue, though obviously you may still have a leak. The evaporators on these cars are known to leak, and even for a seasoned DIY’er it’s literally an all-weekend job. You have to tear so much shit off just to access it. I’m sure your mechanic can diagnose it.

Hopefully someone else can chime in and help you get to the root of the actual issue.

Thanks for the reply e90yyc, and for the info on the e90 A/C system!

Telling me about the condenser design was really useful info. I had no idea about that variable displacement design from an angled plate and control solenoid. Thinking it was a typical clutch plate style that had gone faulty, I was actually looking to replace it or search for a clutch repair kit.

I also search e90 evaporator replacement and watched some time lapse videos of the interior/dash tear apart. It looks like a 20 hour nightmare, but strangely something I would not shy away from attempting myself.

Keeping my fingers crossed that I don't have a leak from the evaporator, but an easier area to access and repair. If an A/C system repair and recharge solves my fan operation issue I will be

Once I know what I'm dealing with I will share it.

[WhoGotTheKeys?]

Just an update on my fan issue which I shared about a week ago...

Mechanic did the temperature tests and electrical testing to conclude that all fan and cooling system parts were fine, just as I told him from all of my multimeter circuit checks and temperature checks. No fan action whatsoever, even with A/C button on.

He then went ahead to test the A/C pressure. Found the pressure to be low - approx. 0.9 lbs when it should be 1.3 lbs. He topped up the pressure and retested. The A/C started blowing cold air (obviously), but more importantly the fan started working normally again! Yesss!!!

I am super relieved and happy that she's good to go on longer trips now as I had to stick to really short drives for quite some time. I commented that it is really stupid that a cooling fan stops working because the A/C pressure drops a little (below a threshold) without tripping a code. It's a really dangerous thing as it can go slowly and unnoticed causing repeated overheating and damage to many parts (note: I am now getting new exhaust manifold catalytic pipes and post-catalytic oxygen/lambda sensors put in because they were all toast -- expensive job). He said this is how it should be set up. Not sure if I will ever understand or agree with that.

Anyways, I hope this helps someone who is having fan function issues in an e90 and has checked every component and remains scratching their head. Do not neglect the A/C system... check the pressure and make sure it is where it should be.

[n54saffa]

I am also struggling with my n54 335 radiator which doesn't turn on when I reach 125c/257f. I have tried removing the oil temperature sensor to see if that would trigger the radiator fan to turn on but it doesn't. The only way to get the fan running is by turning the A/C on.
I can't believe that previous post solution was to top up the A/C to get the radiator fan running without A/C. The two things have no relation to one another.
Has anyone got a solution or any explanation to how A/C pressure would cause the radiator fan to not work when the A/C is off?