Hi, I've isolated it down to something in the Aux Fan circuit that is causing my battery to die after a few days. Any idea what it might be (resistor pack or relay)? When I disconnect the fan connector (just in behind the grill and in front of the aux fan), the battery no longer drains/dies. I'm not sure if the resistor pack is shorting somehow or if one of the relays is kicking on occassionally. Any help would be much appreciated.
Just replaced whole aux fan unit. Not a hard job, old one was dead.
Worth noting, got a unit from AutohausAZ, and it came with resistor pack installed. A Behr OEM, perfect fit, shipping included for $158.
Score! Finally found someone having the same issue as I am with the aux fan. According to your signature, you have a 1999 e39 (as do I) which means that there is no resistor pack and no set of three relays that control fan speed. Input to the fan is simply ground, 12V, and a PWM signal from the ECM that controls fan speed. I am assuming the problem is something to do with the fan motor/controller that is causing it to draw current (about .5A) when the car is off, in which case I'm guessing that the most reasonable approach is to just replace the fan ... but I'm not certain yet.
-Doug
Im at my wits end! I have replaced both reistors, tried 2 different BRAND new relays in the ebox, and ALL fuses in glovebox are good and fuse 75 is good. The fan low speed only comes on when i remove the relay and jumper pins 87 and 30, i can make high speed come on by pumping the pins at the temp switch connector at the radiator. What is going on?? Does the coolant have to be at a certain temp for even the low speed to kick on? maybe the DME measures this?
Electric Fan conversion, 840Ci thermostat, Dinan style CAI,de-screened MAF, Dinan transmission chip, 255lph LS1 fuel pump, drilled slotted rotors, 3.15 differential, Bel rx65 radar (hard-wired). Hemi Killer!
Don’t know if it’s specific to your car , but you get the idea of the wiring and switches and the relay.
Low speed
IMG_8841.JPG
Medium speed
IMG_8842.JPG
High speed
IMG_8843.JPG
So I have a 2003 540i that has been overheating in traffic at first I thought it might be the fan clutch, and still haven't checked the fan clutch while the car is warmed up, but while poking around the auxiliary fan I found that my wires have no plugs on either end and whoever I got this car from nutted two of the three wires on either side together and left the other two unutted. I only have 6 wires, a red and yellow, brown, and black from the sensor switch and a red, green, and black from the fan. The red and yellow wire was nutted to the red wire and the green to the black. When I touch the brown wire that is left over to the black wire coming from the fan the fan spins at what I assumed to be its highest speed like it's on crack this happens whether my key is in and on or laying on the grass next to me also the wires heat up. I tried other combinations and got either nothing or the fan trying to spin backwards... any answers?
Electric Fan conversion, 840Ci thermostat, Dinan style CAI,de-screened MAF, Dinan transmission chip, 255lph LS1 fuel pump, drilled slotted rotors, 3.15 differential, Bel rx65 radar (hard-wired). Hemi Killer!
If your Aux fan isn't working and you have the AC on it can overheat, especially in the summer.
Your Aux fan should only have 3 wires, +12v, ground, and a PWM wire that controls fan speed from the DME.
Sounds like someone used fan from a non tu engine or used an aftermarket fan.
I can't speak for the older style 3 phase fan but for the newer variable speed electrical aux fan there is a way to test if it's working using INPA.
Strangely it's NOT found by selecting E39 - 5 Series --> Body --> Air conditioning IHKA IHR
Instead you can get to the test by choosing E39 - 5 Series --> Engine --> (Choose your Engine Type)
In my case this is ME 7.2 for M62 MJ 99
Once in the main menu choose <F6> Activate --> <F2> Activate relay TEV --> <F3> el. fan
If the fan is working you'll hear it click a few times in the first 5 seconds before it spins up and increases speed to max over about 15 seconds or so before cutting out and slowing down to a stop.
If the fan works it will point to the culprit for the AC not working elsewhere... In my case to the system not having enough gas pressure.
This can also be verified in INPA...
E39 - 5 Series --> Body --> Air conditioning IHKA IHR
<F5> Read Status --> <F1> Analog input
The voltage for the pressure sensor is how the DME determines the pressure as one of the conditions that must be met for activating the AC compressor clutch via a final stage control.
e39_IHKA.png
I would have attached the whole document for the 2001 changes to models that this image is from but it's over 1MB and it gets blocked.
I just wanted to say I used your method of testing the fan (after I installed the same unit you did with no signs of life) and it worked! It does not turn on on its own, so that’s a mystery, but at least now I know the fan itself works on both speeds and it isn’t defective. Did you find out why it doesn’t turn on on it’s own? I replaced the temp switch and checked the fuses (the relay not yet) but it won’t come on. My ambient temp sensor is missing, but upon further inspection I realized the ac high side pressure switch is broken (literally, idk who did it and how). Could these cause the inability of the fan to function on its own?
I just replaced the entire fan assembly on my 2002 530i. The fans on the earlier 528 models are different than the later model 525/530/540 in design. Here's the DIY guide for the replacement, which involves removing the front bumper.
link: https://youtu.be/CazRTB9J0uw
Hello all, hate to revive a dead thread like this but I am having issues with my aux fan as well.
My car is an 02 540i. The fan does not turn on at all, even with A/C on in 100 degree (F) heat. The fan spins freely, and it does spin on start up for computer test. No errors are thrown in the computer either.
Where should i look first?
Jump back to Post #18 as your's is a later model with a different Aux fan than the earlier "preface lift" models. The DME sends a square wave signal to the fan to increase or decrease speed. There is always 12volts at the motor. IF NOT then check/replace fuses and relays. Any scanner (Foxwell 510 for example) will show you where the fault is. Fan assembly, Fuses (NO POWER) relays (no Power).
Get a scanner, a volt ohm meter and TEST, don't guess.
Current Garage Highlights
2003 525iT TiSilver
2002 M5 TiSilver
1998 528i KASCHMIRBEIGE METALLIC (301) (Goldie)
Former Garage Highlights
2005 X5 4.8is
2004 325iTs (2x)
1973 Pantera L
1971 Dodge Dart Swinger "Lite Package"
1970 Dodge Challenger T/A 340 Six Pack Alpine White
1970 Dodge Challenger T/A 340 Six Pack GoManGo Green
1969 Road Runner 383
1968 Barracuda Formula S 340 Sea Foam Green
I thought I would add that I made a thread about repairing the motors for free, the title is "Fixing a Early E39 / E38 Auxiliary Fan / Pusher Fan Motor For Free".
I have read this entire thread and trying to figure out what is happening with my Aux fan. In short my 01 525 overheated I found the 19yo radiator developed a crack. Replaced the radiator hoses and thermostat as well as installed an electric Spal fan.
Using an Ultragauge my temps max around 215F which lead me to check my Aux fan. I noticed it was not spinning when I would turn on the AC. If I turn the AC on and disconnect the fan and plug it back in it sometimes spins for a bit but then stops. I am hoping its doing this because of a loose wire or maybe a failing fan.
I ended up getting a new Behr fan nd want to test the fan before removing the bumper. With the car and AC running I try to connect it but the fan does not spin at all. It could be due to not having a lot of slack and a loose cable but could I be doing something wrong? I have tested the connector with a multimeter and was able to detect 12v and ground. I am going to borrow a multimeter that can detect Hrz to see if I am getting a PWM signal. Luckily its getting into winter and I still have the electric fan but I would still like to get this figure out.
Welcome to the forum CFLip2X.
With the AC on the aux fan isn’t going to come until the temp sensor in the lower radiator hose gets hot enough for the DME to send PWM signals to the aux fan.
Thank you. The car should have been up to temp I tested it after my drive to work. I did replace the sensor the old one had a bad o-ring so decided to get an extra since I was not sure of the type of ring. Even if it is not up to temp I should be able to connect the old one assuming it still works and just use a heat gun to warm it up and trick it switch on the fan. I have been so busy haven't had time to test with a multimeter will try today.
AUX Fan comes on at LOW mode/speed whenever the AC is ON by an input from the AC controller and the engine computer combined AND the outdoor temp is above 10C - as shown on the display in the instrument cluster AND it supposed to stay on ALL THE TIME. In other words, if you turn AC on while its LESS than 10C (50F) outside it will NOT engage, if more than 10C (50F) - it will...
Last edited by siny528i; 11-12-2020 at 10:28 PM.
BMW CCA 434493
Hi,
Saw a fan error:
Fan moves alright by hand but will only jump a little when activated with INPA (80% here):
https://youtu.be/HMjtZRVaseU
Is there something else to check or is the fan surely broken?
Thanks.
I posted this in another thread recently and seems it belongs here too:
The DME will check the operation of the aux fan at startup and periodically during operation. If a fault is detected (doesn't move at startup test) or fails during operation, it will disable A/C
The aux fan (and A/C) will also not run if the car is too cold. So, if your ambient temperature sensor is faulty - the car will think it is -40 degrees outside, and it won't run the A/C OR the aux fan.
The most common failure mode I have seen regarding PWM fans is the control wire, they often get brittle and break near the fan connector. They may work intermittently. This can often be diagnosed with INPA by commanding the fan on and then adjusting the PWM fan wire, moving it around - if some positions it works, others it doesnt, the wire is the problem.
I see about 5 wire failures for every other type of failure related to the aux fan. It's always the first thing (along with ensuring ambient temp is reading correctly) I check on cars with A/C faults or aux fan faults.
The aux fan can cause overheating. The fan clutch isn't always enough to cool the engine on it's own. It's usually enough to keep it from going nuclear, but if it's hot enough, a lack of working aux fan can cause the car to exceed the intended operating temperature of the engine. It is a "supplementary cooling fan" per BMW. Used for A/C, but also for cooling.
As it sounds it works intermittently, I would check the PWM fan control wire (the small wire, it goes to DME X60004 pin 4)
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