[foghat]

Hey all,

So my radiator fan is running full bore. It is loud. Only comes on (this loud) when the AC is on. Will happen in under a minute after starting my car. Goes away about 10-20 seconds after turning AC off. Comes back on pretty much immediately after turning AC on.

It is not terribly hot right now. About 20C.

Cobb AP is not showing any codes and my coolant levels are good.

Could this be a sign my water pump is going? In other posts I've found on this (where fan is indicator of failing water pump), there are usually codes being thrown - though I guess these might be the codes AP can't read. And I couldn't tell for certain if in the 'water pump' cases the fan would come on even with the AC off. Where as on mine, no AC, no fan.

I'm not sure when this started happening, but I noticed it 2 days ago. I had my AC recharged about 2 weeks ago, and I am fairly certain it was not doing it then.

Any thoughts?

[6MT_Addict]

Sounds like the water pump to me, how many KM's on your car?

[foghat]

48,000 km (~30,000 miles). I did some more testing. I'm not sure if the fan is full bore or not anymore from a cold start (it was for sure when I shut my car down after driving home from work), but it is pretty loud. If it were the water pump, I don't think the fan would turn off when I turn the AC off? And then back on when I turn the AC on.

Some one else just told the me the the fan will always run when the AC is on, I just don't recall it being so loud before. I just dunno.

Here is a video I took of it. At about 7 seconds kicks in even a little louder.

[RazRokz.!]

Water pump

[willsull80]

30,000 miles is a little soon for a water pump. Do you have INPA? you can activate the pump independent of the DME with it and check its operation.

[Dylanize]

Originally Posted by foghat

Hey all,

So my radiator fan is running full bore. It is loud. Only comes on (this loud) when the AC is on. Will happen in under a minute after starting my car. Goes away about 10-20 seconds after turning AC off. Comes back on pretty much immediately after turning AC on.

It is not terribly hot right now. About 20C.

Cobb AP is not showing any codes and my coolant levels are good.

Could this be a sign my water pump is going? In other posts I've found on this (where fan is indicator of failing water pump), there are usually codes being thrown - though I guess these might be the codes AP can't read. And I couldn't tell for certain if in the 'water pump' cases the fan would come on even with the AC off. Where as on mine, no AC, no fan.

I'm not sure when this started happening, but I noticed it 2 days ago. I had my AC recharged about 2 weeks ago, and I am fairly certain it was not doing it then.

Any thoughts?

Hey sorry I cant help, but i seem to have the same issue, pleas keep me updated in your findings. Thanks.

[foghat]

I don't think it is water pump. If it were, I would expect the fan to be going all the time. Not just when AC is on. Apparently fan always running when AC is on is completely normal. I just don't remember it being so loud before.

I'm not sure this is an issue anymore. This morning after my drive into work, the fan was not terribly loud. It was a little cooler out, so probably makes sense. Still, can't help but feel it is running louder/faster than it did in the past.

But again, only when AC is on.

What is INPA? Would be nice if there was someway to view the coolant temp. I would have thought I could do with with cobb ap, but didn't see a parameter that looked like it would be coolant.

[willsull80]

How long have you had the car? As for it running on high with the AC on its going to do that because the condenser needs air flow for the AC to condense the freon back into a liquid. Chances are the fan is working off if head pressure on the AC system

[foghat]

I've had the car for just over a year. I think there may be a typo in your last sentence. I am not sure what you are saying there.

And just realized I posted this to the wrong forum. Oh well.

[6MT_Addict]

INPA is BMW software that links with your vehicle, you can do a bunch of stuff with it, more info in the coding area.

Ya 45000 is really soon for the water pump, you should still have factory warranty, just take it in and have them look at it. It could be your fan is rubbing against the shroud or something but that's just a guess. There's also a way to isolate the water pump by turning on the vehicle without holding the brake pedal so the car is on but not running, hold the gas pedal all the way down for like 20 seconds or something and it activates the water pump. Similar to the reset for throttle input learning or whatever it's called. Anyone know more info on this?

[willsull80]

I'm saying your fan runs faster because its hot and your AC system needs to remove heat from the car. The way it does this is by running the fan faster to transfer heat from the freon in the condenser ( it is located i front of your radiator). Basically like the fan on your house AC just on your car.

[willsull80]

To add to that if you live dusty area or have a high bug population your condenser may be getting dirty causing a higher freon pressure which the causes the fan to run faster to compensate for the lower air flow across the coil.

It may be as simple as going to a car wash and making an attempt wash the coils out with the sprayer.

[willsull80]

Ok now I am home now and not driving, I can give you a little more plain explanation.

this is a quick review of how AC's work before I explain the fan speed.

Freon has two states vapor and liquid.

inside the car Freon goes from a liquid to a vapor and absorbs heat from the air. this part is called the evaporator hence liquid evaporates to vapor.

outside the Freon goes from vapor and condenses to a liquid when it ejects the heat it picks up in the car. this part is called the condenser.

both of these coils require a fan to transfer heat i.e. the cold air that hits your face and the hot air that burns your hand on the outside part.

the indoor blower is controlled by the operator and the compressor and condenser fan(cooling fan for car) react to your choice of air speed/amount of heat in the car as well as how hot it is outside.

If the car is hot you will want lots of air as fast as you can to keep your face from melting, so you turn it on high or the Auto setting puts the fan on high so it goes into over drive attempting to remove heat from your hot BMW.

In turn the electric fan outside has to eject this hot air that is inside the car and as a added bonus cool your engine off as well... its a pretty awesome thing.

So now that it is hot again the fan runs at a much higher speed because it is doing all it can to keep the car and the AC cool, even if the car isn't up to running temp it is being controlled by a "transducer" (this magic thing converts pressure into voltage output for the AC control module to see) on the AC liquid line to tell the fan to speed up or slow down depending on the pressure(heat) in the system

This is most likely why your fan does what it does when it does it....

I hope this clears it up a little for you if not.. Google or the Dealership may be your best option.

[6MT_Addict]

Lol seriously is there anything you don't know?

[foghat]

Originally Posted by willsull80

Ok now I am home now and not driving, I can give you a little more plain explanation.

this is a quick review of how AC's work before I explain the fan speed.

Freon has two states vapor and liquid.

inside the car Freon goes from a liquid to a vapor and absorbs heat from the air. this part is called the evaporator hence liquid evaporates to vapor.

outside the Freon goes from vapor and condenses to a liquid when it ejects the heat it picks up in the car. this part is called the condenser.

both of these coils require a fan to transfer heat i.e. the cold air that hits your face and the hot air that burns your hand on the outside part.

the indoor blower is controlled by the operator and the compressor and condenser fan(cooling fan for car) react to your choice of air speed/amount of heat in the car as well as how hot it is outside.

If the car is hot you will want lots of air as fast as you can to keep your face from melting, so you turn it on high or the Auto setting puts the fan on high so it goes into over drive attempting to remove heat from your hot BMW.

In turn the electric fan outside has to eject this hot air that is inside the car and as a added bonus cool your engine off as well... its a pretty awesome thing.

So now that it is hot again the fan runs at a much higher speed because it is doing all it can to keep the car and the AC cool, even if the car isn't up to running temp it is being controlled by a "transducer" (this magic thing converts pressure into voltage output for the AC control module to see) on the AC liquid line to tell the fan to speed up or slow down depending on the pressure(heat) in the system

This is most likely why your fan does what it does when it does it....

I hope this clears it up a little for you if not.. Google or the Dealership may be your best option.

Thanks for all the info! While I had a decent understanding of how AC works, no where that detailed of an understanding. Thanks for that.

I am quite certain at this point my water pump and thermostat are fine. I monitored the coolant/water temp on the way home, trying with AC on and off and it never got beyond 218F and was usually around 212-214 or so. And it is absolutely consistent, turn off AC, fan turns off. Turn on AC, fan turns on.

However, I am still wondering why the rad fan speed is so high compared to what it used to be. I remember listening for the infamous n54 engine tick in the past and hearing it no problem. There is no way I'd hear it now with the way the rad fan is going.

If it were 90+F out, I'd get it, but we are talking 77-78F here. I am almost certain the fan is running faster than it was in the past. I am just not sure when this started.

I've read in other posts that a faulty temp sensor could be the cause of this. Any thoughts?

Also, I didn't see anything sitting in front of my rad (condenser). Should it be visible through the kidney grills?

Thanks.

[willsull80]

Yeah most likely but the fan in AC mode is looking at the pressure transducer as well as temp. Something tells me your fan is looking at the pressure and is ramping up from there. My fan blows really hard on my car but I live in Alabama where it is always hot... All I can say is take it to the stealership and let a SA tell you a bs line and go back home pissed off... I still think its something normal or simple fix... But I'm 100% sure it is tied to the AC system in some way if it only reacts to you turning it on and off.

Sensors go bad all the time. Try this turn the car on and then turn the AC on low. See if the fan ramps up and down, or just goes wide open and stays that way. If that happens you may just need the AC control module reflashed by the dealer. Or some type sensor may have taken a dump on you and is sending a false signal.

[foghat]

Originally Posted by willsull80

Yeah most likely but the fan in AC mode is looking at the pressure transducer as well as temp. Something tells me your fan is looking at the pressure and is ramping up from there. My fan blows really hard on my car but I live in Alabama where it is always hot... All I can say is take it to the stealership and let a SA tell you a bs line and go back home pissed off... I still think its something normal or simple fix... But I'm 100% sure it is tied to the AC system in some way if it only reacts to you turning it on and off.

Sensors go bad all the time. Try this turn the car on and then turn the AC on low. See if the fan ramps up and down, or just goes wide open and stays that way. If that happens you may just need the AC control module reflashed by the dealer. Or some type sensor may have taken a dump on you and is sending a false signal.

The rad fan speed increases and decreases with the AC fan speed. If I set the overall AC intensity of Soft (was on intense/high) that helps too. If the AC fan speed is low, the rad fan is all that loud.

At this point I think i am going to leave things be and see how she goes.

[willsull80]

Well to me that tells me it's modulating the fan in some sort of intelligent way, which is how it should be working.

[thegr8grizzly]

Could someone inform me of where the temp sensor is that the cooling fan uses? my issue is similar but i dont believe it has to do with the A/C. My cooling fan is on, full bore, 100% of the time that my car is running. I had a slight front end accident that broke a piece off of the shroud, but the fan is completely intact and runs fine (maybe a little too fine now...). I 'm pretty sure it wasn't like this before the accident, but ever since i got it back from the mechanic (he replaced my radiator among other things) the fan has been on constantly so I'm not sure if he screwed up plugging it back in or not. Any thoughts? hoping it's not the water pump...
(it's a 2008 328xi with 76k miles and the N51 btw).
THANKS