aircon - fan when should it fire up?
 

Hello to all, cut a long story short (long story included below to be honest) how long after you turn on the air con in the cabin should the large fan in front of radiator fire up? Air con guy says I may need new one due to below observations….

summer kicked in early here 33C too hot, and my aircon refrigerant was low again takes two years to need a top up or refill, still not sorted it, on my visit this time to another guy who deals with aircon and car electric repairs, the minute he finished and fired up engine and turned aircon on to about 20c he said I had an issue and pointed to the large fan in front of radiator not spinning….before he could go any further it kicked in and started.

He told me to keep an eye on aircon in cabin and if I did not feel it cooling to turn off the aircon, as the fan maybe faulty and so not cooling the condenser so not cooling the car.

I did a couple of more tries whilst driving on the way home and it seemed to be working fine.

Got home turned off engine then tried after 30mins whilst checking fan in front of radiator, this time it took anywhere between 15-45 seconds to kick in, on most occasions it tried to spin and seemed hesitant as such….I also noticed that upping the fan speed on the air con output controls in the cabin made it ‘kick in’ faster.

No idea how quickly the fan for air con purposes should fire up or what else maybe wrong?ANY input great

If the fan is faulty it can be read with software that is specific to BMW. It will not trigger an OBD II code since it is not emission related. The fact that your fan does come on means the fan is working. You can command to run the fan if you have the right software.

But to answer your question when the engine is started the DME sends a command to the fan to turn it on ( it may make 1 or 2 revolution). The fan sends a signal back to the DME that it has turned on there are no fault.

The fan only comes on when there is insufficient air flow to cool the condenser. If you are driving at speed, the fan is not needed to cool the condenser and may not come on (depending on the outside air temp).

The speed of the fan is controlled by the DME. It uses a pulse signal to vary the speed of the fan. That is why there are three wires to the fan, a plus wire, a negative wire and the signal wire. The longer the pulse the faster the fan will run.

Uapllnight-superb explanation much appreciated, just to get this straight, the fact that the fan jerks slowly to try and start 1 or 2 or 3 times as i called it acts hesitant, and does not fire up as soon as the aircon is switched on is not that much of an issue? I am going to try on wifes bmw e46 and see if hers fires up straight away....again thank...

Ditto upallnight..the variable speed aux fan used after 9/1998-up (like in the M54/M52TU/M62TU/M57/M57N/N62) is controlled by the ECU/ECM/DME which sends a PWM signal to the aux fan to turn on under specific circumstances (approx 4-5 criteria).

The aux fan is not like the 2 & 3 stage aux fans used in earlier BMW models with the M62/M52/M50/M30 engines.

And at start up...the aux fan will turn on briefly as a test for the DME to know that the aux fan is okay:

Just stealing OP's thread for a minute, to state that i don't have an aux fan at all on my Europe spec. 2004 4.4 (N62).
Still, my aircon has always been working flawlessly. Even in 30 C. (86 F.) it provides plenty of cold air.

Yes...it is freaky that the n62 doesn't have the aux fan...especially when you come from previous BMW ownership that did.

It was a great curiosity for me when I got my 06 4.4 ... I searched high & low for the aux fan...I thought that it may be hidden (sandwiched) between the radiator and the radiator fan. I eventually gave up and asked the forum if I was nuts. :D (well...I'm probably still nuts...but no, the N62 doesn't have an aux fan in front of the radiator). :)

Proof? See image of hvissoer4's engine bay...not the absence of the aux fan in front of the radiator. :)

http://www.xoutpost.com/attachments/...g-dsc00753.jpg

Holy cow, that's one clean engine bay you have there Qsilver7 , and THANKS to all for the super break down on how the aux fan works, anyhow as a test and probably not the best comparison, I tested on wifes bmw e46 318i 2002 model and low and behold the fan behaved the same on switching on the air con....wish that was the only query re her car...damn think keeps chewing and fraying the serpentine belt....another story though that

You have one of the pulley misaligned. Check the alignment.

Can anyone point me to where the main power fuse for the AUX fan is located. My fan wiring was damaged in an accident and spliced up without the 3 pin plug by the panel shop. The 12v supply to the fan is dead. If I connect the fan 12v supply directly the fan starts up and its speed is controlled by the ECU.

All four 50 amp fuses in the fuse box have continuity. Nothing is labeled AUX fan in the fuse box.

E53 is a 2006 diesel.

On USA model E53 with the 3.0 engine the BIG 50 Amps fuse for the Aux fan is located in the fuse panel in the glove box. An easy way to test to see if you have a blown fuse isa to remove the connector from the fan and with a volt meter set to volts one of the big lead will be 12 volts and the other big lead will be the ground. Insert the probes into those two terminal and you should see 12 volts.

Mine was eating belts. Turned out that the shop I used to replace the water pump when it went and I was far from home did a poor job. They used sealant on the gaskets which through off the alignment ever so slightly.

Good info here but,

To my knowledge, m52tu engines in E36/7 and E36/8 chassis still used the old fan system. BUT, these were "parts cars":). On mine I have, E30 rear suspension, E36 front suspension, and an engine from an E46:)

Update,

Found the fuse for this. Its hidden under a removable clipped in cover on the top of the glove box fuse box. I had to remove the glove box and then unbolt and lower the fuse box. Under the cover are 3 flat fuses bolted in place (8mm socket nylocs) . The one for the AUX fan was a 60 amp unit.

The 4x red 50 amp fuses on the front face of the fusebox were used for other circuits.

Sound more like the fusible link and not the aux fuse. On my X the aux fuse was one of the 50 amps red fuse.

I have confirmed that the later 2006 E53 diesel (Australian delivery) do not use any of the 4 larger red fuses. The fusebox has some additional fuses on the top of the fusebox that can only be accessed by removing the glove box and unbolting the fusebox unit so it can be lowered down.

The fuse used is a "MIDI" format originally designed by Littel.

Picture of the underside of the fusebox. The red/cyan wire on the right is the one that goes to the Aux fan.
https://dl.dropboxusercontent.com/u/...s/IMG_1419.JPG

The upper side of the fusebox has these fuses. The one for the AUX fan is missing as I was getting a replacement.

https://dl.dropboxusercontent.com/u/...s/IMG_1421.JPG

Picture of the new fuse in place

https://dl.dropboxusercontent.com/u/...s/IMG_1424.JPG

AUX fan now works again. I hit a kangaroo which mushed the front up pretty bad. The fuse must have blown when the AUX fan wiring was mushed up in the mess.

Hi all,
I am having A/C issues in my '04 X5 3.0i E53. I have pulled all 4 red 50amp fuses under glovebox and all are good(NONE of them are labeled as "AUX FAN" whatsoever). I have a free-spinning aux fan(no binding) got continuity on it(+/-), got 12V reading from power harness to fan, fan does not rotate upon start-up or Max A/C activation or at normal op temp, etc.
Unplugged lower rad hose sensor, fan did not go on.
Is there anything else that is affecting the operation of the fan, causing these symptoms? Do the US non-diesel E53's have this MIDI format fuse wired in? I also have ared/cyan wire in my harness. I am kinda stumped.
Would Final Stage Resistor affect aux fan operation, above and beyond when A/C is commanded on......like upon startup test???

Any help or guidance would be appreciated.
Thanks

Steve

Unplug the high pressure AC switch located in the hard AC line next to the compressor. The fan should spin full speed over a few seconds almost like a jet engine taking off. If it does not spin, chance are the fan itself is bad.

Hi all,
Overboost, thanks for the reply. Unplugged high pressure switch and fan roared on, smooth rotation, no bad sounds/smoke!(I did this several times and fan operated every time, but shut down upon reinstalling switch)
So, now I know fan works:thumbup:
Plugged connector back in and compressor sounded like it engaged, but fan slowed to a stop and I assume compressor then shut down again. Is it my switch?
Thanks for help!


Steve

Usually not the switch but at least you have ruled out one of the most common failures (the fan). Time to put some gauges on it and see what it wants.

Today’s AC problem and the fix. AC / air conditioner / Auxiliary Fan

X5 2004 3.0i. 130K miles.

Symptom: AC blowing cool or at ambient temp. 100 degree day during golf trip (La Quinta, CA) – very poor performance. I thought the AC system had a leak. Very sad.

Need Help. I appreciate any recommendations on a brand for a new AC auxiliary fan.

What I did.
Inspected the belt, AC clutch, and 2 service valves, and AC auxiliary fan.

Good. Belt and clutch were operating.
Good. 2 service valves (common leak point) had dust under the caps and no residue (not leaking).

Problem 1 . AC auxiliary fan controller connector was UNPLUGGED! Wire was hanging. I felt very stupid because I was the last one to touch it. Thought that I found the problem, but wanted to get the AC serviced by a pro since it had been over 5 years. It was 60 degrees so no easy way to test the AC operation. But, I’m feeling very lucky.

Indie Mech. $315 (SoCal)
Evacuate and recharge AC frion + add Dye to test for leaks.
No visual issues. Frion level was on the low side of the scale(potential bad sign)

Problem 1 (again). Auxiliary fan NOT WORKING. Failed. Sh*T the Bed . . . . .nuts!
AC performing ice cold while car is moving (Thank the maker!), and coolish while stopped (no air flow due to failed Aux. fan).

Mech. recommended new BMW Aux Fan ($1,000 to replace. $550 parts/ $450 2.5 hours); and return in 1 week to visually inspect for leaks (look for dye with a special light ).

Outcome: I will likely replace the AUX fan myself once I zero in on a non-BMW brand fan that costs less than a new set of golf irons.

When I replaced mine I got a new Behr unit off fleaBay for under $200. You have to pull the front bumper but it honestly takes about 1 hour start to finish. :thumbup:

Thanks for the info Overboost.

Hi all,
So, my compressor clutch IS engaging. Tested low side pressure as I watched the clutch engage(pressure began at 100ish). Clutch engaged and pressure didn't hardly move at all. Fan does not turn on at start-up for test run or when A/C is on Max. There was NO cool air blowing out, even with comp clutch engaged. I assume, since pressure is so high on low side, that it indicates no leak(would there be low to no pressure if leak?).

That pretty much points to a bad compressor.