I have been trying to avoid this,but I have exhausted my not making a new thread options. I have found several threads pertaining to failed aux fans on the E46 323i manual trans vehicles, but none have any pertinant information in them besides, “replace this and replace that.” I was dumb enough to purchase a new aux fan, but pulled my head from my ass when i realized there was another potential issue before I installed it.
The Heart of the issue:1999 BMW 323i 5-Speed Manual
I have a new Aux Fan unit which does not fix the problem of the fan not turning on. I have checked over the normal culprits i.e. the WP the T-stat, but these are working accordingly. I do have power and ground to the aux fan, but what i really want to know is:
-What is the Aux fan signal wire signal supposed to look like (in hz or volts - have read spec is between 10-100hz)
-What is the proper test procedure for the coolant temp sensor located in the lower radiator hose. (cannot find resistance/operation information)
-What is the possibility that the Engine Computer is to blame
-If the coolant temp sensor is in fact bad will it prevent the fan from working at all even if the A/C is turned on.
As it sits right now I have good power and good ground, but no fan regardless of the A/C on or if the coolant temp rises above “acceptable” (approx 230 deg F). The fan will also not turn on to run it’s preliminary fan test. The radiator is also in good shape and flows well. I will note that the vehicle will cool off once you are moving (even slowly) or if you rig the aux fan to stay on permanantly.
Any insight would be greatly appreciated! Thank you in advance!
Do you have a Bentley manual for the e46 3-series?
I believe the Aux fan is supposed to come on immediately if you put the A/C on (it is this way on the e36 chassis). Perhaps try turning that on to see if it turns on the aux fan.
If the value that the aux fan signal wire is supposed to see is the same as an e36 I could look up the value for you.
yeah, whether the A/C is on or not there is no fan. Also, it seems like there is supposed to be a fan test sequence upon turning the ignition on that I don’t get either… Unfortunately the difference is vast between the e36 and e46. The ECM controls the fan speed via a pulse sent to a control box on the fan shroud at some 10 to 100 hz thus making it about 15 speed variable… I have none still, lol!
1: what about your relay/module for the fan? Did you check hi-side power going in?
2: its not an Aux fan. Its your primary fan because your car never came with a mechanical clutch fan. Just saying.
Well, Slow-J, if you read everything beforehand you’d have the answers! LOLOL. I’ll shoot you the short version:
All Power and ground is good.
The control module for the fan is loacated on the fan shroud
The fan is controlled by the Engine computer (there are no relays or anything beyond a fuse which is ok.)
I do not know what the pulse is supposed to look like for the fan signal and would love to know (or if someone has some meter to measure ~10 to 100hz)
Also I would love to know what the test/resistance is for the coolant temp sensor located in the lower radiator hose.
I wonder if that coolant temp sensor being bad would cause the fan not to work.
well Gay-son, sure it would, if it reads open or closed whichever, itll be either full bore or off. can u unplug it? if so, can you jumper it and see if it kicks on. if it does, there ya go sport. lol
:lol no relay will switch at 10-100Hz… so it’s probably controlled by a transistor in the ECM or another module somewhere. To measure 10-100Hz, you’ll need an oscilloscope or some multimeters have a frequency meter in them. You might be able to set a true RMS meter to AC or DC and see if you get a change in voltage when the fan should turn on. But if you switched fan with a new one and the wires that go from the ECM to the fan are good, either the ECM is bad is not receiving a signal to turn the fan on.
If your old fan shorted out it’s possible you fried the transistor in the ECM.
edit (just read wizards last post):
Yeah the module is probably a transistor. Has power, ground and frequency signal from the ECM. I wouldnt jump wires unless you unplug the module. The signal is most likely a DC square wave.
I dont really care if the ecm is cooked on that portion, but I suppose that means there could be other problems with the ecm, which I’m hoping it’s not. The most common thing to go bad is the fan control attached directly to the fan motor. It reads that signal and it makes that signal up based on the A/C high side switch and the coolant temp switch. I guess if anyone knows what the coolant temp sensor resistance is supposed to be I can rule out the possibility that it’s throwing the whole system off. If it is good then I guess it’s time to call flex-a-lite lol!
DAMN IT FUCKER! LISTEN! unplug the sensor, and jumper it. Its gonna read either high resistance or low for it to blow full blast. Give it both scenarios and see if you can get it to kick on, if not, then its not the sensor. That way you can test fan, module, and wiring, if it kicks on that is.
sorry i dismissed it because i already did that. Now because I don’t know what the resistance on that plug is but some people were talking like you had jumper the plug and not just remove it. It show a +5V to the sensor but I still don’t know what the voltage output range is or the sensor resistance is supposed to be.
If the A/C’s on and sufficiently charged the fan should come on, eventually.
The signal wire’s difficult to check but in this case you may not have a choice.
Here’s an excerpt from a training manual:
"The electric cooling fan is controlled by the ECM. The ECM uses a remote power output final stage (mounted on the fan housing). The power output stage receives power from a 50 amp fuse (E46 - located in glove box above the fuse bracket). The electric fan is controlled by a pulse width modulated signal from the ECM.
The fan is activated based on the ECM calculation (sensing ratio) of:
-Coolant outlet temperature
-Calculated (by the ECM) catalyst temperature
-Vehicle speed
-Battery voltage
-Air Conditioning pressure (calculated by IHKA and sent via the K-Bus to the ECM)
After the initial test has been performed, the fan is brought up to the specified operating speed. At 10% (sensing ratio) the fan funs at 1/3 speed. At a sensing ratio of between 90-95% the fan is running at maximum speed. Below 10% r above 95% the fan is stationary.
The sensing ratio is suppressed by a hysteresis function, this prevents speed fluctuation. When the A/C is switched on, the electric fan is not immediately activated."
This may not help much, but hopefully it’ll give you some idea of what you’re dealing with.
you want to find someone with INPA or DIS and then go ahead an try to turn the fan on manually. If that works, I’d suspect the DME. If it doesn’t, I’d suspect the wiring. INPA is a factory tool, which means you’d have to find (someone with) a pirated copy. DIS is the dealer tool, which means if you can make friends with your dealer (or well equipped indy shop) and get some info.
I’d double check that the lower hose sensor is working and that there isn’t air in your system. I don’t know the resistance to temperature mapping, but you can pull the values from DIS or INPA pretty easily. I’m not sure which temp sensor the instrument cluster will use for its ‘hidden’ display, but I suspect it’s the one in the head.
I just dont read german so I can tell what comes with the more expensive one. I want to basically be able to reset/test the fan circuit and possibly other stuff. Diag equipment like this is useful for more than just this though so it may be worth picking up…
99% likely the DME. Outside the DME, the entire(fan) system is pretty bulletproof and unlikely to burn out. BMW overkill in that area. IIRC if anything is wrong with the temp sensor and wiring, it’ll pop a body/chassis code.
E46 wiring is a blast to diag(sarcasm, yup it’s in there). Been going through diagrams on the S54 drivetrain for months now myself :’(.
Ahh yes the good ol S54, enjoy the part where they mislabel some of the wire colors, lol. You should really check out the guy that swapped his 323 to the S54 drivetrain with SMG trans. He did a pretty good job, but noticed there were a few wires that were off on the factory diagrams.
I am having some other issues with the car that I am noticing as well, which leads me to believe there are greater issues here. I have an alternator whine in my speakers and my gauge cluster basically freaks out sometimes when I turn on the headlamps. I should note that there are HIDs on the low beams and capacitors do not stop the cluster from freaking out. This is actually a new symptom because the HIDs have been in the car for more than 3 years. I am also getting a break wear indicator on the dash even though the brakes are still in very good shape. I believe it may just be time to pull the entire front of the car off and remove the engine, trans, and subframe to follow a few wires around in the engine bay area and freshen up a few hoses and plastic bits.
You wouldn’t happen to have access to a professional diag tool for BMW cars would you. I want to see if I can activate the fan through the DME or if I am getting the proper signals where they are needed. I may be able to isolate the real cause of the problem then.
That I do not unfortunately. I don’t work on enough of them to justify the cost of the tool, and even the ones I typically dig into are E36’s where most of the diag doesn’t require one. I do have a bosch hammer from when I used to service P-cars alot for PCA, but my programming is only for Porsche 964, 993, and GT3’s/Turbo’s. At $2800 even that was a stretch for me .
Second paragraph speaks natures of a faulty ground. Alternator frequency backfeeding through the harness because it found a better path than the one it should be taking. BMW loves to stash a few of the common ground points way under the dash, and up on the firewall. I’d even just check the neg batt cable and/or the main engine ground strap. Typical german car crap in reality.
The cluster thing is another issue. BMW clusters are a friken mini computer themselves and have a mind of their own. Don’t know much about them myself, other than just replacing with a known good unit first for testing before digging through harnesses for diag.
I would certainly test the DME, or if possible swap out with another car(will possibly require key transponder coding in the DME, never swapped e46 DME’s before.)
I’ve been ripping through the S54 diagrams to attempt a twin DME setup for the kit car V12 in the event one does sell. Same thing Porsche used to do on the 956/962 with the Motronic and basically turned a flat six motor into two three cylinder engines mated at the crank. Every sensor doubled up. Not many other options for running quad C.V. VANOS other than that, Motec M800, or OBR! I have an entire E46 M3 harness here and it’s by far the knarliest electrical mess I’ve encountered. I haven’t even begun to cut it open yet. Looks like it’s gonna be a blast. I’ll take note of those wire coding mistakes though, thanks for the heads up on that
Holy crap, sounds like wuite the serious project! I can’t find the page that this kid had up a while ago about his M3 swapped 323, but I’m sure you’ll find it if you do a quick search… of course if that’s even relevant to your project!
I have been looking through the wiring diagrams and taking not of where some of the stuff for the DME and body harness is grounded and they are all fairly accessible. I’ll have to hunt down all the grounds first and then get into some hard core wiring diag/rebuilding a lot of worn out crap. I think I’m going to find someone with the GT1 Software then completely rip my car apart. It will most likely be a shell sitting on the lift for a couple days, lol! Maybe now is the time to look into my S54 swap, like I have the $$ for that!
