Cooling Fan Issues (1999 750iL)

[Seedyrom]

I bought a 1999 750iL with this issue, after cranking the aux fans run constantly. Does anyone have pictures of the wiring and could someone tell me their location. I'll check the relay too because this car has a wiper relay issue and that's on the right side of the car under the computer cover near wipers. This car has several gremlins to tackle. Thanks

[dworthy]

I bought a 1999 750iL with this issue, after cranking the aux fans run constantly. Does anyone have pictures of the wiring and could someone tell me their location. I'll check the relay too because this car has a wiper relay issue and that's on the right side of the car under the computer cover near wipers. This car has several gremlins to tackle. Thanks

Chap, you need to start a new thread, as your car is very different from the OP's.

[bmwdirtracer]

https://www.newtis.info/tisv2/a/en/

Your electric cooling fan is controlled by a pulse-width signal from the DME. The fan unit always has full time hot and full time ground, and the circuitboard/module built into the fan unit translates the signal from the DME to achieve different fan speeds.

IF the electric cooling fan is truly running at full speed whenever the key is on, you need a new fan unit. There is no relay involved.

What "gremlins" do you have? On an E38, if you have assorted electrical issues, quite often the ignition switch can be the culprit. I haven't known this to be true of the wipers, and certainly not the aux fan, though.

[Mayorchuck]

I bought a 1999 750iL with this issue, after cranking the aux fans run constantly. Does anyone have pictures of the wiring and could someone tell me their location. I'll check the relay too because this car has a wiper relay issue and that's on the right side of the car under the computer cover near wipers. This car has several gremlins to tackle. Thanks

Sent a request to have this started as a new thread. In the meantime, have you had your system filled recently? Over filling the a/c system will cause the aux fan to run on high if the a/c is on or not on your car. As Chris stated, the relay is incorporated in the unit itself starting with the '99 model. The temp sensor on the lower radiator hose also regulates the fan. You can try unplugging that sensor but I don't believe a bad sensor would cause it to run if the a/c button was off. The only time I have seen this happen was from too much pressure in the system.

Chris, while I would not rule it out, I have never seen the electric fan influenced by the iggy switch either.

Need more info on your gremlins. The wiper relay sits at the bottom of the ebox. It is often a victim of water if the drain hole is clogged. You need to physically pull up the plug the relay sits in and inspect the bottom of it for corrosion.

[Seedyrom]

My first gremlin was I bought the car with the dashboard removed & speedo package disconnect. After reconnecting all 4 plugs the fan
no longer runs all the time. So I'm thinking the temp gage is tied to computer data plus data from the engine temp sensor to serve as a
backup warning to tell the driver about overheating. Do you know if this is the case? The windows would not roll up or down with the speedo
unhooked but I could use the remote door unlock to raise lower or put key in outside key lock, even the truck lock worked.

Also the wipers now also work. Weird but I'm going to unplug the speedo to see what happens. Will post update.

[bmwdirtracer]

A huge number of the car's computers rely on the speedometer signal. Why would you unplug it now that more things are working?

I highly recommend that you continue CONNECTING all you can, and THEN try diagnosis and clearing codes on the rest.

Do you have a BMW specific diagnostic scan tool which connects to the 20-pin underhood diagnostic port? You need this.

[Seedyrom]

The AC hasn't been touched, though I bought the car recently, the previous owner said it was filled last summer after he swapped out a bad V-12 for valve carbon build up issues. 1st owner beforehand (I'm 3rd owner) ran 87 octane and never changed the plugs, oil change every 12k or worse. The basic do nothing driver! Newer engine has 100k so all is well except I bought knowing the cats are clogged so I'm looking at Magflo and possible EWS delete if needed or I'll go with O2 delete on rear 2 sensors.

I checked, no water under the computer area, did see a pair of drain holes so someone tackled that. Other gremlins are the power tilt telescoping wheel doesn't work, nor cruise control so I'll work on that next.

- - - Updated - - -

I'd only unplug to test if the fan activates then reconnect.

I don't have the BMW scan tool so I'll look into that. Where is the underhood diagnostic port located or what is it near?
Thanks.

- - - Updated - - -


Does the aux fan kick on at high temps only or when AC is running etc? I'm trying to adjust to new car noises, normal sounds and
what is normal for this engine.

[bmwdirtracer]

Electric fan should start within ~30 seconds of turning on the a/c, if the a/c works. It otherwise should come on if and when the engine gets too hot. The switch/sensor in the lower hose controls this part. The engine-driven clutch fan is the primary cooling fan, and if it's very weak or failed, you need to replace it urgently.

I pretty much never send members to the model specific forums - EXCEPT the E38 forum. They have really knowledgeable people there, so please share your questions over there too. Your flagship V12 car is pretty rare, and some of the more erudite owners at that forum are more intimately familiar with certain issues than most pro BMW techs, including myself.

EWS delete? Are you using the right abbreviation? That's the anti-theft driveaway protection system, and it works very well, and is generally quite troublefree. Are you having some issue with starting the engine?

[Mayorchuck]

I have to admit I'm lost here. You keep referring to the 'speedo package'. I can only assume you are referring to the cluster/IKE, that would have to be removed to take out the dash. That should have nothing to do with the windows. What 4 plugs are you referring to? As I recall, there are only 3 on the back of the instrument cluster. I can't even think of a bus issue that would tie those together.

As far as the electric fan, I put together a thread some years back on HVAC related issues. The fan info is towards the bottom. I will also post an image that shows the bus systems. It shows E39 but is the same for your car.



https://www.bimmerforums.com/forum/s...eral-HVAC-infobus.jpg

[Seedyrom]

Somehow I forget to check this thread so from what I can tell is the unplugged speedo or cluster/IKE prevented the computer from getting a temp reading from one of the three coolant system sensors because when I unplug the cluster/IKE as its properly called the aux fan kicks on and runs while the engine is running but when I plug the cluster/ike back in and restart the engine the aux fan doesn't run unless I turn on the AC. So maybe its part of a backup system to run the aux fan? Relay was fine as was the sensor at the radiator. As for the windows it was coincidental, the battery had been unplugged for several weeks according to previous owner so all is well now, windows work with key fob or by switch or with key in door lock. I bought a 750iL with no interior
other than the seats and the cluster/ike............I called it the e38 Stevie Wonder Edition Bought a full interior for $750 so now I've got a complete car and the Cats are next.

Sorry about EWS delete was noobish of me, ews delete is for e36 and older so my bad, jumped the shark on that one. I am having intermittent issues when starting so its most likely the key switch because sometimes I get a click and no start and other times the engine starts fine. Saw this with a 95 e38 switch too. I'll pull the steering wheel panels and order a news part. I know how to pop the housing piece off the back of the key switch to start with a screwdriver so long as the key
tumbler doesn't lock and freeze in the wrong place.......that happened with the 95 740i.

[bmwdirtracer]

If you intermittently get a click rather than a starter turning, you probably have a loose or dirty main power or ground between the battery and the starter; including the engine main ground, and the B+ jumper terminal underhood.