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Discussion Starter · #1 ·
Hi All,

I'm trying to diagnose why my aux fan is not coming on as usual on start up or when I switch the ac on...

First thing I thought to check was the fuse to the aux fan, reading around on the web and checking my Bently manual I still cannot find it. I know its a 50amp fuse and I have found one of these under the bonnet, right hand side near the front bulk head in a box next to a couple of relays.

Ive got a 1998 740i European car...

Anyone who nows where it is I would really appreciate a thread..

Thanks in advance.
 

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Discussion Starter · #4 ·
Guys I could do with a few thoughts on whether or not I am diagnosing why my aux fan is not working its not as simple as I thought it was going to be...
History is that the ac wasn't that cold and found out that the aux fan was seized solid, British weather not that hot so wasn't too bothered and picked up a second hand one the next time I was passing a BMW scrap yard....I fitted it last November and didn't have much reason to check to see if the ac was any better or not... but British summer is hot this year and could do with the ac working. So when I realised the aux fan was still not working I did a few tests based on what I could find on the web...

There is a 50amp fuse some where which might be blown was my first thought...still haven't found it but have worked out that its not the fuse because there is a +12v feed at the connector between the fan and car, this feed switches on and off with the ac switch on the centre consol...so fuse good where ever it is...still cannot find it, if anyone knows where to look would appreciate your thoughts...I cannot find it in the xbox area.

So testing the car side of the connector then the ac switches the black/brown wire on and off.
Testing the fan side of the connector then applying 12v to the black blue wire and the fan works.
Applying 12v to the black red wire and the fan works
Applying 12v to the black wire and the fan does not work

looking at the connector then the black brown wire on the car side feeds the black wire which explains why the fan does not come on when I switch the ac on.

looking on the web then the black blue wire looks like the high speed for the fan, black red is the slow speed and black is the medium speed, so this makes me think the resistor has gone on the fan...so this will fix the ac if this is the case.

However this will not fix the fact that there is no live feed from the car side of the connector when I first start the engine...does this mean that there could be a relay gone?

Any thoughts would be appreciated...
 

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...However this will not fix the fact that there is no live feed from the car side of the connector when I first start the engine...does this mean that there could be a relay gone?

Any thoughts would be appreciated...
Are you confusing the operation of the variable speed fan used on BMWs with a 9/1998-up build date with the operation of the 3 stage (speed) fan use on the 1996-1998 model year e38? The 9/98-up variable speed fan goes through a "check" at start up...the older 3 stage fan does not.

(3 stage {speed} Aux Fan 1996-1998 BMW)


And from the BMW online WDS site...see the image below for the location of the aux fan's 50 amp fuse (#78)...it's located on the right side of the engine bay (perspective from behind the steering wheel) in the E-box:

http://www.bmw-planet.com/diagrams/release/us/e38old/index.htm

{Fuse #78 location - Right Hand Drive}



{Fuse #78 location - Left Hand Drive}

 

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Discussion Starter · #6 ·
QSilver7...thanks for the feedback...I think your right...you have saved me a a lot of time...I've got a resistor pack on order so hopefully that will solve my a/c cooling problem...no need to worry about the initial switch on during start up...thanks also for the link to where fuse 78 is...for some reason the right hand side of my bulkhead is different...so it maybe some where else...no worries...thanks again much appreciated.
 

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... the link to where fuse 78 is...for some reason the right hand side of my bulkhead is different...so it maybe some where else...no worries...thanks again much appreciated.
This image may be a V12...but the V8 should be similarly located on a RHD e38. The link to the WDS used the same image for the M73 and M62 RHD engines:

 

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Discussion Starter · #8 ·
QSilver7 I think I have found the fuse it is in the area you show but based on your diagram I didn't test the circuit correctly...I assumed that the fuse would be for all stages of the circuit but based on the diagram you posted its on stage 3 which explains why I dismissed the fuse as being number 78, I tested it with stage 1 circuit live...will check this weekend but I pretty sure you have sorted it...many thanks
 

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Hi All,

I'm trying to diagnose why my aux fan is not coming on as usual on start up or when I switch the ac on...

First thing I thought to check was the fuse to the aux fan, reading around on the web and checking my Bently manual I still cannot find it. I know its a 50amp fuse and I have found one of these under the bonnet, right hand side near the front bulk head in a box next to a couple of relays.

Ive got a 1998 740i European car...

Anyone who nows where it is I would really appreciate a thread..

Thanks in advance.
Mine was hidden under my steering wheel take the bottom dash cover off then take off the knee crash protector and it was under there Hidden I have a 97 3 series buy I bet its hidden like that look on your fuse pannle cover it'll tell you fuse locations just have to look up what # fuse dos what first
 

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Mine was hidden under my steering wheel take the bottom dash cover off then take off the knee crash protector and it was under there Hidden I have a 97 3 series buy I bet its hidden like that look on your fuse pannle cover it'll tell you fuse locations just have to look up what # fuse dos what first
Nice effort trying to help but...E38 is nothing like an E36 and if you would have read post #2 you would have seen the correct answer including a picture.
This was also a long dead thread and OP left when that happened.
 
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