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Thread: E36 M3 AUX fan not working even after replacing

  1. #1
    Join Date
    Oct 2016
    Location
    Santa Ana, CA
    Posts
    19
    My Cars
    2002 330i ZSP, 1997 M3

    E36 M3 AUX fan not working even after replacing

    Hey guys, I’ve got a 1997 BMW M3, and the aux fan isn’t working. It’s been really hot here in so cal, and my car almost overheated in stop and go traffic running the AC. I replaced the aux fan with a brand new one but it still doesn’t kick in. I jumped the temp sensor on the radiator to turn the fan on low or high setting but neither work. I can hear the relays clicking but nothing happens. I also replaced the two fuses for the AUX fan but it is still not working. Any idea what it could be?

  2. #2
    Join Date
    Jun 2005
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    New England
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    25,402
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    F90 M5; E36 M3 Turbo
    I would provide power and ground directly to fan side of harness and go from there. Likely wiring, relay, fuse or sender. Beware relays interchange only with same color relay or you can short your electrical system — they are often not wired like Bosch generic relays.

  3. #3
    Join Date
    May 2012
    Location
    Central Wisconsin
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    640
    My Cars
    '94 325i, '93 325is
    If the relays click for both high and low speed then you know the sensing side of the circuit is working properly. If the fan doesn't run check for power at the relay socket, if you have power at the relay sockets then use a jumper wire to see if jumpering the relay socket works.

    Here is a screenshot from the ETM. When I say to jumper the relay socket what I mean is putting a wire between 30 and 87. To test the normal speed you will need to either have the high speed relay installed or jumper from 30 of the high speed relay to 87 of the low speed relay because of how they are interlocked to switch speeds. If you have 12V at the relay socket terminal 30 but the jumper still doesn't run the fan then likely the ground is disconnected.

    This screenshot is from a 94 so wire colors may not match depending on your manufacture date.

    '94 325i Sedan, Arctic Gray: UUC LTW FW, EVO 3 and DSSR, +.020 Maxsil pistons, ASC delete, Eibach shocks/springs, 16" contour reps 238k
    '93 325is Coupe, Schwarz, work beater 299k
    '89 325i Vert, Alpine White: 5spd swapped. Sold
    '04 Toyota Sienna XLE Limited AWD, In progress swapping to M50/G250, http://www.wibimmers.com/board/index...nna-25i-build/
    '05 Volvo V70 R, 6mt, mostly stock, kid hauler 200k Sold
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  4. #4
    Join Date
    Oct 2016
    Location
    Santa Ana, CA
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    19
    My Cars
    2002 330i ZSP, 1997 M3
    Quote Originally Posted by jc43089 View Post
    If the relays click for both high and low speed then you know the sensing side of the circuit is working properly. If the fan doesn't run check for power at the relay socket, if you have power at the relay sockets then use a jumper wire to see if jumpering the relay socket works.

    Here is a screenshot from the ETM. When I say to jumper the relay socket what I mean is putting a wire between 30 and 87. To test the normal speed you will need to either have the high speed relay installed or jumper from 30 of the high speed relay to 87 of the low speed relay because of how they are interlocked to switch speeds. If you have 12V at the relay socket terminal 30 but the jumper still doesn't run the fan then likely the ground is disconnected.

    This screenshot is from a 94 so wire colors may not match depending on your manufacture date.

    I'm trying to see your screenshot but it doesn't seem to go through :/

    When you say jump the relay socket, do I use the same standard paper clip wire i've been using? Sorry I'm kind of a noob, it just seems weird to put a piece of wire into a socket, did it once when I was a kid and I electrocuted myself hahaha, so I don't want to make the same mistake.

    - - - Updated - - -

    Quote Originally Posted by jc43089 View Post
    If the relays click for both high and low speed then you know the sensing side of the circuit is working properly. If the fan doesn't run check for power at the relay socket, if you have power at the relay sockets then use a jumper wire to see if jumpering the relay socket works.

    Here is a screenshot from the ETM. When I say to jumper the relay socket what I mean is putting a wire between 30 and 87. To test the normal speed you will need to either have the high speed relay installed or jumper from 30 of the high speed relay to 87 of the low speed relay because of how they are interlocked to switch speeds. If you have 12V at the relay socket terminal 30 but the jumper still doesn't run the fan then likely the ground is disconnected.

    This screenshot is from a 94 so wire colors may not match depending on your manufacture date.

    I'm trying to see your screenshot but it doesn't seem to go through :/

    When you say jump the relay socket, do I use the same standard paper clip wire i've been using? Sorry I'm kind of a noob, it just seems weird to put a piece of wire into a socket, did it once when I was a kid and I electrocuted myself hahaha, so I don't want to make the same mistake.

  5. #5
    Join Date
    May 2012
    Location
    Central Wisconsin
    Posts
    640
    My Cars
    '94 325i, '93 325is
    You don't see the wiring diagram? I see it in my post and your quote. 12V won't shock you so a paperclip would work, I use one of these fuse holders with male spade terminals that are about the size of the tabs on the bottom of the relays crimped onto the wires, that way a mistake won't cause melted wiring.

    https://www.amazon.com/Nilight-NI-FH...70_&dpSrc=srch
    '94 325i Sedan, Arctic Gray: UUC LTW FW, EVO 3 and DSSR, +.020 Maxsil pistons, ASC delete, Eibach shocks/springs, 16" contour reps 238k
    '93 325is Coupe, Schwarz, work beater 299k
    '89 325i Vert, Alpine White: 5spd swapped. Sold
    '04 Toyota Sienna XLE Limited AWD, In progress swapping to M50/G250, http://www.wibimmers.com/board/index...nna-25i-build/
    '05 Volvo V70 R, 6mt, mostly stock, kid hauler 200k Sold
    '85 Toyota LandCruiser: Lifted, gas hog. 205k

  6. #6
    Join Date
    Oct 2016
    Location
    Tenerife, Spain
    Posts
    628
    My Cars
    1997 BMW E36 323i
    Also check the fuse box for the fuse numbers. Recently we had a tough case and eventually discovered the main aux fan fuse was in the cabin somewhere, and not in the fuse box next to the engine.. If it shows a number that's higher than any of the numbers in the fuse box below the hood, then you know you have to look in another fuse box (somewhere in the cabin, don't remember where, but the thread was quite recent and I went all the way to help and we finally resolved it).. I found the thread. Here it is: https://www.bimmerforums.com/forum/s...-automatically . Also contains multimeter tutorial, so should get you started.
    Last edited by ed323i; 08-07-2018 at 07:13 PM.


    1997 E36 BMW 323i
    (European) 275k km (171k miles), with following small mods:

  7. #7
    Join Date
    Jun 2010
    Location
    NY
    Posts
    9,079
    My Cars
    1997 328i
    A paper clip in place of the relay may be a bad idea since several amps will flow through the clip and it may get very hot. Make a proper wire with terminals, but you could do the paper clip if it were only for two seconds and you had pliers to pull it out very quickly.

    After you've done that and the fans do come on then your problem is most likely the relays. Listening for a click is not a sufficient test for a relays properly operation. The contacts can burn and no current will flow through the relay. Bench testing it is the proper way of going about it. remove the relay from the car, energize the coil with 12v, while energized use a multimeter to test the resistance across the switch terminals, should be less than 2 ohms.
    Attn. NEWBIES: Use the search feature, 98% has already been discussed.
    Click the search button, select "search single content type", select the "e36 sub forum" specifically, try the "search titles" then try the "search entire posts".

  8. #8
    Join Date
    Oct 2016
    Location
    Santa Ana, CA
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    My Cars
    2002 330i ZSP, 1997 M3
    Just solved the problem. I took my car to my mech since I don’t have much time to solve the issue atm, he was playing with the fuses and he ended up switching out fuse # 40 and it worked! I have no idea why that fuse played a part the fan, I thought on 6 cylinder models that fuses 16 and 41 were what operates the fan. I guess I’ll never know...

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