BMW E38 E39 Electric AUX Fan Not Working? Diagnosis And How To Fix...

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BMW E39 Electric AUX Fan Not Working? Diagnosis And How To Fix...
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[@danielpoitras7494]

Nathan, what do you mean when you unplugged the battery and touched the 2 wires together?

[@jameshensley1222]

I'm disagreeing 100% on main fan...in Florida it does help. Remove it and engine gets warm in heavy traffic in slow and stand still. Put clutch fan back in and no overheat... that aux fan is primarily for secondary ac cooling to bring down freon in condenser so it doesn't get too hot and expel out the compressor...

[@mikesavage8379]

So what fixed it? touching the battery cables together to reset the ECU after checking fuses, wiring, etc?. You also think you may have a pblm with temp sensor? Also, don't buff out the lenses. buy new pre-facelift lens covers on Amazon for like $100. They will snap on your existing housings. I like the ones with the clear corners - get yellow bulbs. Change your adjusters while you have them apart. Link: a.co/cVQqq75

[@carlosdelgado4825]

I don’t have ac , and no aux fan , so far no problem and I drive in the summer 2002 e39 two years straight

[@djroyd]

Hello Nathan i have the '98 528i and i drove it on the freeway with the ac on and stopped at a drive thru to get food and the temp gage went to red and as soon as started driving it the temp gage went back to normal. Could the aux fan be the cause of that problem? Please help!!

[@kurzjames]

I actually think the clutch fan is fairly robust. My aux fan almost never spins with the clutch fan working

[@chuck1607]

Great information Nathan. I just bought my '98 BMW @ auction for $575. It had a bad radiator, bad overflow bottle. Now I believe the cause of the troubles to be fan related. I'm suspicious of my coolant temperature sensor. I will keep trouble shooting. Thankq for putting these videos together.

[@kevinjean2702]

Finally a video about a 97-98 model. My issue was the a corroaded plug and connector for the fan sensor on the radiator. Thanks Nathen

[@_Greasyzoku_]

What’s the little black box???? Does 94 525 e34 have one???

[@cfp1479]

Nathan. My A/C on my 2003 540 M sport isn't working. It's holding a charge. Aux fan never comes on. I replaced the little box and the temp sensor. Fuses are good. Do I need to replace the entire fan? Thanks for your help.

[@luigi8962012]

Nathan's BMW Workshop are the best BMW videos, Nathan keep up the Excellent work!

[@sanjinred]

The Aux fan is actually for the heatexchanger of the AC system, not the engine

[@sanjinred]

The clutch fan is enclosed in a plastic frame which draws air into the engine bay at low speeds and draws hot air from the radiator to the back and down out below the transmission, thats why you see the big opening there. Aerodynamic forces under the car create a slight underpressure at higher speeds which help to draw hot air out. In the front you’ll see small openings in the cover which are hinged, the clutch fan makes them open at low speeds and draws air in. The aux fan is to take away extra heat from the ac heat exchanger and if you read german it is perfectlt described in bmw wire diagrams etc. But the aux fan certainly helps at high ambient temp with AC on and if not the ac hestexch could heat up the radiator and engine coolant circuit but that is at extreme ambients

[@DrDavidNahali]

Hi: I just changed my fan on the BMW 525 2001 cause the old one was dead. But when I plugged in the new fan it started running. even when the engine is off and is stone cold. Basically, it runs all the time. I disconnected the fan relay and it is still running when plugged in. I have to unplug it to make it stop. Is it a bad fan? Thanks

[@d235353]

Hey all i have something else to report about the Electric fan!!!! .. I just discovered.. i noticed on my fan that there wires & terminals that lead in to the fan motor control unit where completely corroded and had gone green with oxidation where they are not protected from the elements ... the black wire literally fell off as I took the wire harness out of its clipping thats how bad it was .. if you have a aux fan problems please check this first the wires are connected in by little metal snap in clips and the oxidation was terrible on my fan and certainly was not helping then upon closer inspection I tried to remove the fan control and all the wires basically just fell off and broke away where the plastic and the terminals where so brittle

[@PowerHousePowerHouse-tk8ug]

Well didn't none this info helped me to fix my fan on my 1998 528i. I changed everything and I even touched the battery cables together and still nothing. They came on one while having these issues and never came back on again.

[@Stian2001]

I can guarantee the problem is the fan itself. Most likely original bmw fan that’s almost 30 years old. Replace it with a mahle fan and a new fuse and you should be good

[@andreiput9492]

hello nathan, you comment that the clutch fan is close to useless. could you demonstrate the clutch fan removal and replace with the electric only fan for e46? I presume it would be the asme for E39.

[@BassBrotherBuild]

How is the easiest way to test to see if my aux fan works? I've never seen the fan turn on but I have cold ac. I tried to bypass and it didn't turn on then I seen this video and you say you can't just wire it direct cause of the resistors. Any help would be appreciated

[@albeee8030]

The black box you mentioned if its damaged & not working how u explained how do you test tje "black box" to know whether its bad or not?

[@hugoherrera209]

Hi Al Beee do you have the part number of that "black box". Thanks

[@bargla]

it's a "bad smell sensor" and it is usually oiled inside from the engine gunk. There is a sponge inside that gets dirty over time and you have to clean it. After that it should work fine

[@d235353]

thanx man that really helped me out :) been trying to figure out the fans for a few days .. after the Expansion tank blew on mine.. and kind of helps me pin point the problem to the coolant temp sensor not telling telling the ECU to turn the fan on fresh install of every thing for the sake of levity ...but prity sure that is why now .. btw the black box is a smog detector its designed to slam the cabin vents shut if it detects Fumes coming under the hood i researched that box before kind of weird that it effects the fan perhaps its wired up in series with the rest thats why it shuts down the fan if you unplug it (btw do not go chasing after oil temp sensors there are non only oil pressure and oil level sensors)

[@joshuaj3176]

Nathon, what do you mean when you unplugged the battery and touched the 2 wires together?

[@TheEliteShatter]

I second this

[@TheEliteShatter]

I'm replying again as I did some research and touching the two battery cables together after they've been disconnected from 1-60 minutes (time depends on how long you want to leave it they say or until you can til there's no power in the system) will reset the system though a lot of people say not to do it on luxury cars such as BMW's because of all the electronics. I think this is more of a reason to do it as there's more things that could go wrong and a factory reset shouldn't hurt anything.

[@Dbird613]

I agree with you about the clutch fan. I have a 2002 E39 M5 and I've always had overheating issues especially with the clutch fan. A few days ago the clutch fan was stuck engaged, and I was afraid it was going to grenade as I've heard from other forum members. So I took it off and wanted to do an electric fan conversion as I did on my Titan using a Volvo/Ford Taurus e fan. Since I needed to go to court to new Jersey for a speeding ticket the following day, I did not have enough time to to wire and install the e-fan, and figured since I'll be on the highway most of the time, I'd have enough air moving through the radiator to keep the car cool. So I did a 1000 mile trip and the whole time my car maintained 79C/174F without any issues. I've driven it even though traffic without the clutch fan or an extra electric fan, and my car has not overheated even once. Am still going to add the Volvo fan in place of the clutch fan, but I too came to the same conclusion as you, that the clutch fan does very little to cool the engine. My S62 even revs faster and idles better. Thanks for the video.

[@touring4973]

Thanks! Nathan for all your work! Very much appreciated here.

[@rodneyhendricks8260]

WHAT DO YOU MEAN WHEN YOU UNPLUGGED THE BATTERY AND TOUCHED THE 2 WIRES TOGETHER.....BATTERY CABLES?

[@wheatonna]

Disconnect both + and - cables from the battery. Then, touch the two cables together to get rid of any residual charge in the system.

[@HollywoodHornet]

Replaced my fan clutch a little while back, bought that and the tools from your Amazon store. The aux fan in my e38 doesn't work either. Twitches a little when I turn on the A/C. Scanner gives me a code 8D. I'll try that unplug and plug back in trick before I cough up the 150 ish bones for a new fan.

[@TheHeretic435]

About to do mine for 3rd time. 1st time it broke the fan seem to let go. it's only a kind of screw-press fit onto it's mount - got loose and smashed everything around it. Had a used OEM unit put it - 6 months later a piece of plastic sheet on the highway karate chops right into my bumper grill and smashes the lower aux fan shroud, ducts and bunch of stuff. Cracked fan edge going clack clack clack. Glued it and was on my way. Had bumper off only a week ago to secure all the loose stuff and yesterday the glue let go on fan and smashed both shrouds again! I was shopping for all new plastic gear (and cursing), and a kind soul in my BMW line app chat group says yeah I got complete unit, but the motor is blown - you can have it free! Lucky break. It's funny you know, one of those aux fan units are junk with a burnt-out motor, but to buy the lower grille $30, the upper $45, the fan $330, the frame work - $more. nothing is junk on these cars.

[@shanemcmahon6364]

If the temp sensor is bad will it throw a code?

[@cortiz4007]

Is all this information go for e34 as well mine is a 94 525I 5 series I've replaced radiator......thermostat.....and housing....water pump ...hoses...all belts ...I didn't snap that the condenser fan wasn't working...which CHAPS my Hyde...but I will check on what you said ..I hope this works for an E34 too

[@Ayixlia]

I have replaced all cooling system parts such as the water pump, thermostat including the coolant sensor and the temp sensor, but the fan will not turn on, I have unplugged the temperature sensor and turned the car on but still, the fan will not turn on, I have checked fuses, etc and multimeter tested the power to the fan and still nothing. please help

[@dankennedy6925]

really,u cannot bench test a motor on a BMW!as opposed to any other motor on earth,WTF,I CALL BULLSHIT,NO REAL INFO.

[@michaelsepulveda7755]

Thank you for explaining you can't hardwire the fan from the plug....been trying😕😁. Hi fan works but the low has not worked for some time...bad resistor pack? Change the fan or pack??🤔

[@ricorengue]

Hi Nathan my 98, E38 auxiliary fan stops working after 20 minutes I already changed the sensor on the radiator and I was going to replace the small box that you mentioned on this video before I go and buy the new fan also is two green one black relays behind the glove box that the bemmer forums guys mentioned that control the auxiliary fan that might stop the fan from work if you have any advice I appreciate thanks

[@ccmatthew97]

How can you check a fan on a 2001 E 38. 740il ..3 wire fan.the harness to the fan has power but I cannot check small pulse wire,thank you..also did not work car got hot got home let car sit check sensors fuses good then one day I start it fan comes on high and runs to 199 degrees then shuts of and car gets 230 needle moving from the middle still heating up..next day nothing can the fan be good just the resistors going bad??thank you if anyone can help

[@albeee8030]

Is the black box you mentioned is found on the E53 M54B30 style X5 3.0i SAV? ...i have found wire not plugged into anything & i am leaning towards it being from the wiring harness from auxiliary fan on vehicle?

[@dennisrobinson8008]

What if INPA can activate at 10,50 and 90 pct? Coolant sensor in lower hose replaced but fan doesn’t engage unless AC is on? Its an e83

[@charliejones408]

Nathan I have a question. you mention to disconnect the battery and touch the 2 cables together, What cables are you talking about? The neg and pos cables together, how would that do anything with no juice from battery? I'm confused?? I have a 1997 5401, I checked under the glove box and found the 50 amp fuse but that's it, is there another hiding somewhere? Thanks Charlie

[@chadriddle3517]

Damn Nathan I’m so glad I watched this I did not know that stupid climate control box will stop the fan from working !!!

[@michaeltinajero8014]

The auc sensor right? For like 75 bucks?

[@chadriddle3517]

@@michaeltinajero8014 yes , idk how much for mine from junk yard for a few bucks

[@georgemalek3398]

Hey Nathan, great video and condenser fan diagnostic. The ONLY one that makes a correlation between the controller reset and the a/c fan operation. I will give it a try as my 2001 x5 3.0 A/C only works when the cooling system gets up to kick on temp and engages the condenser fan. Does not come on thru A/c circuitry. No pwm voltage on small wire to fan.

[@ethiopianeyes]

Mine is wired to the fog light. Bought it like that. The fan has 4 wires. My car is manufacturer date 2/99. harness has 3 wires. But stopped working or burnt out when the ignition switch when bad.

[@danielpoitras7494]

I have a 2001 740i. If i unplug the sensor on the lower hose and jump the wires together, will that turn on my aux. fan?

[@albeee8030]

With respect to the 14 cylinder head bolts, i am aware they stretch thus need replacing. Am also replacing the bolts that go in where dual vanos is ➡ i think its 4 bolts there...two at or near corners and two in the piece between or just below secondary chain area? Im about to order the bolts but wanted to know if im actually buying more then the 14 bolts thanks guys....

[@fishfire_2999]

The big plug on the front on pass side when i unplug that and then replug it, the fan kicks sometimes spin 1\4 turn but wont come on, already checked 30 and 50 amp fuse, all other plugs good, is maybe fan bad ? 03 530i

[@tapiolindholm8533]

Hello. My car burns the fuse number 75 50amp and when i put a new one in there comes a little bit of smoke and the fuse is wrecked. I dont know how to go further.

[@chadharmon5716]

Good job

[@veganwally]

Very well said.

[@Adventuredad530]

Love your channel, lots of your videos are very helpful to me. I just got a 1999 BMW 528i

[@lukemalhotra]

My auxiliary fan has recently started making a whining noise when it switches on. And periodically it makes a really loud whine when driving. I noticed today that it doesn't switch on when I turn on the heater but it does when the engine is up to temperature. Should I go ahead and order a new fan?

[@steliyans4340]

This man has great personality. I think he's a wonderful person. That's a lot of helpful advice for free of charge

[@sanjinred]

Its Panama Braun like mine!!! Super rare E39 only color

[@diondreykeelin86]

Keep up the good work I'll keep watching...Also I have a airbox thing too but mines is connected to the end of my alternator found a hole in it today do you know what that plastic part is called?

[@ericericeric888]

May I ask what is the part no. of the box you mentioned at 6:10? That box is find missing on my 97 523i and my aux fan just wont turn on until I turn on the air conditioning.

[@Rjax2322]

Did you ever find out what this issue is? I have the same problem that the aux fan only comes on with the ac on. I have replaced the coolant switch and the temp sensor in my 98’ 528.

[@kg1574]

I have a bmw x5 2005 the auxiliary fan did not work at all, Not when the AC on not even when overheating. I checked the fuse GOOD. I checked to make sure power comes to the fan GOOD. i replaced the auxiliary fan with a brand new fan GOOD. But it is still not working!( What can be done?

[@itsk3hiphop]

Did you swap out the climate control box that plugs into the fan as well? If you already replaced the entire fan and it didn't help, I'd deff check out that box. Nathan talks about it in the video. Should be right above the fan.

[@tstreeter1141]

Good stuff thank you.

[@kribar96]

Wasnt it a blue e39 you said something was wrong with the ecu? So you had just a switch on it.

[@nostudiosound2033]

if the 3rd wire doesn't move from 12-13v to 2-3v when you turn the ac on with the engine running, the pwm signal its not being injected and maybe your ecu isn't working properly for the fan -- thats what I learn from another video and maybe its my case, since everything else its ok.. what you think Nathan ?

[@GearheadologyGarage]

Having that same problem right now

[@aaronhuynh3360]

Also at 6:50 what temperature does the fan normally kick into med speed? I got up to 110 C and didnt want to go faster than low speed

[@marcioreis2648]

Thank you awesome video Nathan..

[@leonardplanckiii998]

Does the clutch fan spin slowly? On 03 525i ?

[@Charlie-wr8cu]

I did jump power to the connector and the fan came on

[@dodisrome608]

Nathan i have an issue with my climate control. For some unknown reason it doesn't turn on and the floor heater is always on. Checked fuses disconnected climate control and it's always on

[@joeyc2490]

sounds like the FSU sensor is bad.

[@Charlie-wr8cu]

I was able to operate the fan at the connector

[@MarioMario-pz1oy]

Nathan cheers for another great video i have a question can i get to the actual bonnet locks this way instead of taking radiator off thanks 👍

[@aaronhuynh3360]

Is there a thermostat i can switch to engage the aux fan at a lower temp?

[@mvelazquez312]

you didn't diagnose nothing but pointed out the components of the ac system.

[@itsk3hiphop]

And going through that system is how you diagnose an issue....thanks for playing!

[@larrycampbell2500]

I forgot to tell you my area code is saying activation map cooler.

[@larrycampbell2500]

Error code

[@AndyNav1]

Thanks for all the detailed explanation.

[@joecruz269]

So if your aux fan dose not turn on will that make your ac not work?

[@stevenburke5494]

Other way around. The a/c will turn the fan on. If it does the fan is good. If not you are screwed

[@joshuaj3176]

Nathon, what do you mean when you unplugged the battery and touched the 2 wires together?

[@stevenburke5494]

Go to the right rear wheel well inside the trunk panel to access the battery. Remove both terminals from the battery and touch them together this might cause a brief small spark and reset the codes and computer which may be telling the fan not to turn on

[@charlieboy501]

thank you for this info that helps alot

[@joshuaj3176]

Nathon, what do you mean when you unplugged the battery and touched the 2 wires together?

[@makgstefan]

he touched together brown and red wires of the battery terminals to reset all the ecus of the car.

[@townman1]

This procedure resets the computer settings , basically clears out the old data.

[@albeee8030]

Nate so if connector is corroded per say what am i to use which cleans that stuff off so its getting proper connection to work as its designed to..in respect to AUX Fan.

[@mikeb2496]

Al Beee Use fine grit sandpaper on the terminals and then cover them with dielectric grease. Promotes conductivity and prevents corrosion.

[@albeee8030]

Mike B thanks brotha..this dielectric grease you speak of here is it very expensive?

[@mikeb2496]

Al Beee nah it comes in really small tubes, I think it was $3-6 dollars at autozone. It comes in little packets with new ignition parts also. Nice bike in your avatar too

[@albeee8030]

Mike B thanks brotha it was a 750 P2 that was vandalized and my insurance totaled it out so i let them take it...i am trying to get X5 fixed, then get me another ole school model Ninja...i loved that bike bro. I had lot of time n money put into it too...only did one track day at NYST in upstate New York off interstate 88

[@albeee8030]

Mike B you got picture or something of what your speaking on brotha?

[@BirdogEd]

Nathan, I replaced my auxiliary fan without taking 90% of the furniture off that you did. I was able to remove the fan by simply bending up the sheet metal above the fan and then bend it back. I have a ‘99 e39 with 208k miles ,with the fan going out at around 175k. Respectfully yours, 😎🇩🇪🚙

[@aaronhuynh3360]

Its for dumb people that dont know what you mean by that.

[@eastpantherbenz]

Every E36/E46 I've bought I had to put in a new clutch fan. I went for the BorgWarner clutch, that thing moves some air! When the factory clutches go bad, they don't pull hardly any air at all. Most of the time you can stop them with your hand.

[@dafugees18]

This was the most direct and clear vid on this issue I've ever seen,..💪👌 please do more #E39 vids! Now if only there was a fix for why my dash and radio doesn't work anymore...

[@doc2419]

I would rather pay the BMW Dealership $2000 to fix it. Yeah, right. First, I would never buy a used BMW ever.