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Thread: Horn Common FAQ, Issues and Fixes

  1. #1
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    Horn Common FAQ, Issues and Fixes

    Hey guys, as you many recall, I've spent a lot of time troubleshooting my intermittent horn on my 1992 E34. Well, I finally found the issue and got it fixed! I figured since I ran through so many different checks in the horn system, I'd post what I've learned and compile a lot of horn tips in one post.

    Common Issues:
    1. Fuse (obvious to most, but check the fuse. should be position 9)

    2. Relay (in the fusebox. usually doesn't go out, but it could)

    3. Steering wheel contact points need cleaning (use contact cleaner, steel wool, fine grit sandpaper)

    4. Steering wheel ground wire. Connects to the slip ring. Connections may be damaged. Repair or replace slip ring.

    5. Steering wheel is not properly grounded. Trace the break in the ground. This was my issue.

    6. The horns themselves are broken (rarely is this the case)

    How the system works (my laymanís interpretation):
    The horn works off of grounding. When you push the horn buttons (the airbag) it grounds the slipring, which gives ground to the carbon pin (that rides on the slipring surface like a record player needle) in the steering column. This ends up giving ground to the relay circuit (probably more complex then that, but you get the idea) and the horn then sounds.

    In troubleshooting the horn system, itís good to have an electrical test light, a jumper wire, and itís really nice, but not absolutely necessary, to have a digital volt meter.

    First verify that your fuse are relays are good. Replace the fuse if needed. You can check the relay by switching it out with one of the adjacent relays. If it still doesnít work then keep searching. From there itís a matter of finding out when and where the horn DOES work. Remove the lower steering column cover and take a jumper wire from the bare door hinge to the carbon pin (while the ignition is in the last position). If the horn sounds, then you know that portion of the circuit is fine.

    If not, then you have a ground issue. Use your voltmeter set to ohms and check and see if there is resistance at the steering column shaft. Remove the appropriate panels till you see the shaft going from the steering wheel through the firewall. You will see a guibo (flex disc) at the joint in the middle of the shaft. Check to see if the lower portion is grounded. If so, check the upper portion. In my case, the ground was lost at the guibo. So I used a jumper wire from one side of the joint, over the guibo, to the other side. This gave my steering wheel ground, a my horn then worked.

    If thatís all grounded properly then remove the airbag (DO A SEARCH) and clean the button contact points. Also verify that the wheel itself is groundedÖ it should be, as it gets its ground from the shaft. Check that the ground wire from the inside of the wheel to the slipring, is connected properly.

    That should cover most of the horn issues. Basically once you know that the horn itself works, trace down the break in the ground. For me, it was that darn guibo!

    Pictures:

    Fuse and Relay


    Contact Points & Ground Wire


    Carbon Pin


    Slip Ring


    Steering Shaft


    Hope this helps someone!!!

    E34 - 1992 M54B30 w/DISA - TRM Chip - Vogtlands - Billie Sports - Beyern Mesh 17's w/Conti DW 245/40/17's - LSD 3.23 - Smilies - 35w 5000k - Projector Fogs - Clear Rears and Corners - Euro Trim

  2. #2
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    Thanks! i'm even printing this one before going to the garage

    Edit: printable version removes the images... who thought of this?!
    Last edited by gcb; 08-29-2011 at 07:13 PM.

  3. #3
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    Glad its useful to you! Idk about the images, I suppose you could download them separately and print them that why

    E34 - 1992 M54B30 w/DISA - TRM Chip - Vogtlands - Billie Sports - Beyern Mesh 17's w/Conti DW 245/40/17's - LSD 3.23 - Smilies - 35w 5000k - Projector Fogs - Clear Rears and Corners - Euro Trim

  4. #4
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    Great info...
    E34 535i/5 (Dirty D)
    RIP E21 320i/4 (Hammerhead)

  5. #5
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    Quote Originally Posted by marct335i View Post
    Glad its useful to you! Idk about the images, I suppose you could download them separately and print them that why
    i just printed the regular page, not the "version for printing" was just shocked that the print version does this

    thanks again for the info. fuse and relays check. going to remove the wheel tomorrow ...and i just run out of conductive grease

  6. #6
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    Quote Originally Posted by gcb

    i just printed the regular page, not the "version for printing" was just shocked that the print version does this

    thanks again for the info. fuse and relays check. going to remove the wheel tomorrow ...and i just run out of conductive grease
    No problem. Try pulling off the bottom column cover and grounding the carbon pin (with keys in the last ignition position) and see if you get a honk.

    E34 - 1992 M54B30 w/DISA - TRM Chip - Vogtlands - Billie Sports - Beyern Mesh 17's w/Conti DW 245/40/17's - LSD 3.23 - Smilies - 35w 5000k - Projector Fogs - Clear Rears and Corners - Euro Trim

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    After I disconnect the battery, wait 15min, and remove the Air bag.... Is it ok to connect the battery again to do those tests?

    Or do I have to do everything, reattach air bag, and THEN connect the battery?
    Last edited by gcb; 09-06-2011 at 05:18 AM. Reason: Automerged Doublepost

  8. #8
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    Quote Originally Posted by gcb

    After I disconnect the battery, wait 15min, and remove the Air bag.... Is it ok to connect the battery again to do those tests?

    Or do I have to do everything, reattach air bag, and THEN connect the battery?
    You don't want to do that, as you will end up with the srs light on. You can test the slipring and carbon pin with just the column cover off and without taking the airbag and wheel apart. You can also test the ground in the column that way as well. If you feel you have an issue with the wheel itself, you have to disconnect the battery and pull the airbag of and test for resistance (ohms setting on mulitmeter) to see if you have ground.

    E34 - 1992 M54B30 w/DISA - TRM Chip - Vogtlands - Billie Sports - Beyern Mesh 17's w/Conti DW 245/40/17's - LSD 3.23 - Smilies - 35w 5000k - Projector Fogs - Clear Rears and Corners - Euro Trim

  9. #9
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    Very nice. Currently my Horn is not working and my SRS light is on. Been this way sense i got it, I wired the horns to a small out of the way switch for the moment so it would work. Could the SRS light being on effect the horn itself?

  10. #10
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    no expert, but from the electric diagrams, the only way the SRS would affect the horn was if it was grounding the circuity before or after the slipring... but then you would have all time horn fun... *IF* i understood the diagrams correctly...

  11. #11
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    It could be that your slipring is not working properly. The slipring is apart of both the airbag and the horn system. Also, your srs light might be on even though nothing in the airbag system is messed up. Once the light is on, even after you've fixed whatever caused the light to come on, it will stay on until you use the special reset tool. Messing with the airbag system, disconnecting or reconnecting the battery while the airbag is removed will trigger the srs light.

    E34 - 1992 M54B30 w/DISA - TRM Chip - Vogtlands - Billie Sports - Beyern Mesh 17's w/Conti DW 245/40/17's - LSD 3.23 - Smilies - 35w 5000k - Projector Fogs - Clear Rears and Corners - Euro Trim

  12. #12
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    can the SRS light be reset with the jumper wire that resets the check engine light?

    if so, i will leave the car sans air bag for some days to fix some other things around the wheel

    *edit: gave that idea up.
    Last edited by gcb; 10-11-2011 at 07:10 PM.

  13. #13
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    couldn't remove the lower cover because my socket kit has everything except the @#*$&#^& 7mm
    other guides told me i would find two phillips screw there instead of one 7mm hex...



    But, i did test the ground. I too do not have signal from one side of the gumbo joint to the other.

    But testing from the top portion of the gumbo joint to the door hinge bolt, I can get the horn to 'work' (it signals the closed circuit chime on the multimeter when i press the horn) with the key on "accessory" position. shouldn't it sound the horn? or the multimeter resistance is enough to not trigger it?

    it's exactly the oposite of what marct335i says on the first post... with the key off, i have ground on the top portion of the shaft (gumbo to wheel) but NOT on the lower portion (gumbo to floor)
    Last edited by gcb; 10-11-2011 at 08:54 PM.

  14. #14
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    Quote Originally Posted by gcb View Post
    couldn't remove the lower cover because my socket kit has everything except the @#*$&#^& 7mm
    other guides told me i would find two phillips screw there instead of one 7mm hex...

    But, i did test the ground. I too do not have signal from one side of the gumbo joint to the other.

    But testing from the top portion of the gumbo joint to the door hinge bolt, I can get the horn to 'work' (it signals the closed circuit chime on the multimeter when i press the horn) with the key on "accessory" position. shouldn't it sound the horn? or the multimeter resistance is enough to not trigger it?

    it's exactly the oposite of what marct335i says on the first post... with the key off, i have ground on the top portion of the shaft (gumbo to wheel) but NOT on the lower portion (gumbo to floor)
    Glad to hear you are getting closer! I'm a bit confused as to what you are describing. It doesn't seem possible for the top half to be grounded but not the bottom. By jumper-ing the top half of the shaft to the door hinge, you've now grounded the shaft (it may or may not have been grounded before). Try grounding the shaft to the hinge and with the key in the farthest position, press the horn (while maintaining the ground to the shaft). You should hear the horn. If not, you don't have a ground issue at the shaft.

    You can also test for grounding at the shaft with your multimeter. You shouldn't need to press the horn to make the shaft grounded. If this truly is the case, then something else is wrong. Best of luck!

    E34 - 1992 M54B30 w/DISA - TRM Chip - Vogtlands - Billie Sports - Beyern Mesh 17's w/Conti DW 245/40/17's - LSD 3.23 - Smilies - 35w 5000k - Projector Fogs - Clear Rears and Corners - Euro Trim

  15. #15
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    i have a mental block on how car engineers use ground for stuff like this sorry.



    common steps:
    1. put multimeter on continuity test
    2. touch one probe on the door hinge bolt

    what i did was:
    Case A:
    3. touch the other probe on the lower part of the shaft (the one that disapears in the firewall... with the striped texture feel)
    4. multimeter keeps silent.

    then Case B:
    3. touch the other probe on the higher part of shaft (green arrow) (the one going into the driving wheel)
    4. multimeter beeps

    then Case C:
    3. turn key to accessory position (one before ignition)
    3. touch the other probe on the higher part of shaft (green arrow) (the one going into the driving wheel)
    4. multimeter silent
    5. press horn.
    6. multimeter beeps.
    7. no horn sound.

    Edit: I really can't see how the flex disc there, being all rubber (?) would give a ground from one side to the other... does it have metal inside? but then woudn't that defeat the purpose of the flex disc? does that dirty i have on mine be causing trouble? is it hard to remove those parts to clean?
    Last edited by gcb; 10-11-2011 at 09:18 PM. Reason: colour!

  16. #16
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    I was just doing a search for this thread to say thanks for writing it (didn't realize there were recent postings). Mine hasn't worked for a while (or it worked when it wanted to) and I wasn't able to sit down and figure out why. Still looking for a definite answer though. Ideas?

    Door hinge + upper part of shaft and it sounds.
    Upper part and lower part jumped and it doesn't sound.
    Last edited by clevertd; 10-12-2011 at 11:47 AM.


  17. #17
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    Quote Originally Posted by gcb View Post
    i have a mental block on how car engineers use ground for stuff like this sorry.



    common steps:
    1. put multimeter on continuity test
    2. touch one probe on the door hinge bolt

    what i did was:
    Case A:
    3. touch the other probe on the lower part of the shaft (the one that disapears in the firewall... with the striped texture feel)
    4. multimeter keeps silent.

    then Case B:
    3. touch the other probe on the higher part of shaft (green arrow) (the one going into the driving wheel)
    4. multimeter beeps

    then Case C:
    3. turn key to accessory position (one before ignition)
    3. touch the other probe on the higher part of shaft (green arrow) (the one going into the driving wheel)
    4. multimeter silent
    5. press horn.
    6. multimeter beeps.
    7. no horn sound.

    Edit: I really can't see how the flex disc there, being all rubber (?) would give a ground from one side to the other... does it have metal inside? but then woudn't that defeat the purpose of the flex disc? does that dirty i have on mine be causing trouble? is it hard to remove those parts to clean?
    I think what might be happening is that the upper half of the steering column is getting ground from the ignition when the keys are out. Once you put the keys in and turned the ignition, it no longer provides ground to the upper shaft. This MAY be whats happening, it rings a bell in my mind. Its really tough to say. You really need to get the lower cover off and try grounding the slipring out to the door hinge. You're best bet is to work backwards.

    Quote Originally Posted by clevertd View Post
    I was just doing a search for this thread to say thanks for writing it (didn't realize there were recent postings). Mine hasn't worked for a while (or it worked when it wanted to) and I wasn't able to sit down and figure out why. Still looking for a definite answer though. Ideas?

    Door hinge + upper part of shaft and it sounds.
    Upper part and lower part jumped and it doesn't sound.
    You are very welcome for the thread! When you say sounds, I'm assuming you are saying that when you press the horn, the horns sound. Thats good. Its a start. Just for kicks try door hinge to lower shaft. If it sounds then as well, you know that there isn't a loss of ground at the guibo. Test the lower shaft for ground, it sounds like there is a break in ground somewhere down the line. I believe there is another guibo on the other side of the firewall, at the U joint between the lower shaft and the power steering gearbox. You might be losing ground there, if so, jumper over the joint to give the rest of the shaft ground. You might have to jumper both the box-lower joint and the lower-upper joint to get ground up to the wheel. Good luck and let me know!
    Last edited by marct335i; 10-12-2011 at 02:48 PM. Reason: Automerged Doublepost

    E34 - 1992 M54B30 w/DISA - TRM Chip - Vogtlands - Billie Sports - Beyern Mesh 17's w/Conti DW 245/40/17's - LSD 3.23 - Smilies - 35w 5000k - Projector Fogs - Clear Rears and Corners - Euro Trim

  18. #18
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    Don't know if i'm just being double dumb now... but it's does not make sense to me that the bottom part of the steering shaft should have ground... i mean, it's bolted to rubber all the way, isn't it? there shouldn't be any metal from that point on to the chassis.... i think.

    I guess it's perfectly normal for it to not be grounded. but it hurts my head since that not only had ground for you, but it also fixed your problem...

    edit:
    more newb question: what should i use for the grounding? speaker wire? i have some 14 or 18 gauge around.
    Last edited by gcb; 10-13-2011 at 02:16 AM.

  19. #19
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    Quote Originally Posted by gcb
    Don't know if i'm just being double dumb now... but it's does not make sense to me that the bottom part of the steering shaft should have ground... i mean, it's bolted to rubber all the way, isn't it? there shouldn't be any metal from that point on to the chassis.... i think.

    I guess it's perfectly normal for it to not be grounded. but it hurts my head since that not only had ground for you, but it also fixed your problem...

    edit:
    more newb question: what should i use for the grounding? speaker wire? i have some 14 or 18 gauge around.
    It's still connected by metal at the joints. The ground is from the steering box etc. Trust me when I say that if the lower column isnt grounded then you'll have no horn. 14 gauge should work. You can use zip ties.

    E34 - 1992 M54B30 w/DISA - TRM Chip - Vogtlands - Billie Sports - Beyern Mesh 17's w/Conti DW 245/40/17's - LSD 3.23 - Smilies - 35w 5000k - Projector Fogs - Clear Rears and Corners - Euro Trim

  20. #20
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    Didn't really have too much time to get greasy, but I did a quick check on door hinge to lower shaft and the horn didn't sound... soo time to look lower?


  21. #21
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    Quote Originally Posted by clevertd
    Didn't really have too much time to get greasy, but I did a quick check on door hinge to lower shaft and the horn didn't sound... soo time to look lower?
    Sounds like you lose the (temporary) ground at the upper guibo for sure. I'd fasten a jumper wire from one side to the other. Then try grounding the lower to the door again. You should be able to sound the horn, being that when you ground the upper you can and now that you've jumpered the lower, you know you aren't having a break in ground at the guibo anymore.

    Now, the issue still seems to remain, that you don't have ground to the lower (and even if you did you would lose it at the upper joint, PRIOR to you jumpering over the joint, but you should have that fixed now). I'd go lower now to the guibo at the steering box and lower shaft joint. You probably are losing ground there as well. Jumper a wire over that and try your horn.

    Hope this helps, it can be a real maddening process. I feel for you!

    E34 - 1992 M54B30 w/DISA - TRM Chip - Vogtlands - Billie Sports - Beyern Mesh 17's w/Conti DW 245/40/17's - LSD 3.23 - Smilies - 35w 5000k - Projector Fogs - Clear Rears and Corners - Euro Trim

  22. #22
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    Man, that was more of a headache than it needed to be.

    I guess I didn't have the wire tight enough around the upper and lower shaft the first time I tried it. I kept going back and forth between the lower ujoint at the steering shaft, cleaned all the dirt off it, checked for grounds/continuity, checked and rechecked. Thought it was the lower ujoint at the steering box when I decided to start from the beginning again.

    Wrapped the wire around the lower shaft and the upper and removed the ground from the door hinge and it sounds! What threw me off was my digital voltmeter would give me a continuity beep when touching a different part of the upper shaft than where I ended up putting the wire, but when I put the wire there, it didn't sound. Changed positions, and bam.

    I don't think any of my neighbors are too happy about me honking 4 times at 8AM, though.


  23. #23
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    i'm still with the battery out of the car, so can't say if this was the only cause, but sure as hell wasn't helping.

    My horn slip-ring was covered in what i believe is very old dielectric grease (or any other insulating grease) that resulted in a total insulation of the connections.

    removed the wheel, removed the spliring assembly, separated the horn and airbag rings, left the horn overnight in simple green. wasted some time scrubbing the cruft with a shop towel.


    (fear my toy multimeter)

    before cleaning, multimeter didn't even detect a closed circuit when 1mm apart! now it's from 0.1Ω to 0.8Ω when testing the furthest path... not perfect, but better. think i needed to scrub it with some steel wool that i couldn't find... i will just let the new carbon pin work it's way over time.
    Last edited by gcb; 10-23-2011 at 08:48 PM.

  24. #24
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    Quote Originally Posted by gcb View Post
    can the SRS light be reset with the jumper wire that resets the check engine light?

    if so, i will leave the car sans air bag for some days to fix some other things around the wheel

    *edit: gave that idea up.
    no, you need a special reset tool. Most of the tools like the Peake SRS tool and the B800 from China work only from 1994 and younger.
    Last edited by shogun; 01-09-2016 at 09:54 AM.
    Shogun tricks and tips for the E32 series are HERE!

  25. #25
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    Sorry to bring up this old thread but it's better that starting a new one.


    I just bought a 92 535i last week and the horn does not work. I have visited this writeup lots of times, going thru every step posted in this thread, troubleshooting every possible angle possible for a few days now. Here's what I have done:


    *Tested ground from the door hinge to the carbon pin, horn works. That eliminates the possibility of a bad fuse and relay.


    *There is continuity from the door hinge when grounded to the steering wheel, horn works as well.


    *Cleaned ALL contacts and points of contacts including ground terminals, carbon pin and back of the slip ring.


    *Bought a slip ring from PnP today, along with a steering wheel as well ($38 for both) -- slapped it on, plugged in the airbag and placed the airbag in with the torx screws in the back halfway in. Pressed the contact points in front of the airbag and it WORKED! However, after I tightened the torx screws all the way in, it stopped working again!!!


    Tried to troubleshoot again, could not reproduce it. Kinda gave up for today.


    Any thoughts?
    1999 E36 M3
    1992 E34 535i
    2010 Evolution X
    www.emperormotorsportusa.com

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