Horn Not Working - E46 Electrical Schematics ??

[BTB]

Hey guys,

My horn has been out of commission for a while now. I’ve been working on other projects (refresh rear end) and have had the car at my parents’ place 2000 miles away so this issue has gone by the wayside. Now that I’ve got the car back with me I’m eager to fix this. I appreciate y’all’s input. Here is the data/backstory:

The horn doesn’t sound. All steering wheel buttons work (except the big one in the middle …). A couple years ago I threw an eBay ‘working’ clock spring at the car which didn’t fix it. Today I did some electrical testing/diagnosis:

1. Checked fuses 5 and 55. Both sides of both fuses are powered with accessories/ignition on.
2. Pulled the horn relay (#6 or far right behind glovebox) and bench tested it. Makes the clear/audible click when power applied and makes continuity. All good.
3. Jumpered in the horn circuit post-relay with ignition on, horn sounds (I think one horn might be dead but that’s a different story). What I reckon is the high pitch horn sounds perfectly.

What this tells me is some connection is not good on the low load/signal side of the relay. Not sure what components are involved other than basically the kit at steering wheel/clock spring.

Is there a resource to get BMW electrical schematics? Anyone know how to diagnose the clock spring unit itself? Should I just throw another clock spring at it given the one I put in was not new/perhaps not functional?

Appreciate any input from those with knowledge or experience around this.

Thanks

Brendan

[sapote]

Just like seeing a doctor and provide age, male/female, so month/year built , 6mt/SMG are needed.

[BTB]

Lol not sure if joking ? Anyhow it's a 2003 6MT coupe (Nov '02 build) with 208k on the odo.

[sapote]

The relay connector has 9pin.
make sure pin6 and 8 have 12v ignition ON.
pin5 connected to horns and you had tested it good.
pin4 should be grounded when pushing on the horn button -- measure with ohmmeter (or test light if you know what to do).

[BTB]

The relay connector has 9pin.
make sure pin6 and 8 have 12v ignition ON.
pin5 connected to horns and you had tested it good.
pin4 should be grounded when pushing on the horn button -- measure with ohmmeter (or test light if you know what to do).

I put the relay back in before checking but I’m pretty sure it’s pin 4 not making ground to complete circuit when pushing horn. Something in my horn button/wheel I think but I suppose I better make sure at the relay. Other pins are powered and as I mentioned the horn works when artificially ‘energizing’ the relay aka closing horn circuit.

[JayVee]

There is a main plug behind the wheel liner on the left (drivers) side behind the bumper. Mine was corroded and needed a cleaning.

[Rosie]

Here’s the horn circuit:-




It’s unheard of that all 4 contacts in the steering wheel behind the airbag fail.

[STAATS]

The best BMW Wiring Schematics source I have found at the moment short of having and old laptop all setup with outdated versions of Java and with WDS installed is here:
BMW WDS Online (bmwteka.com)

There is some other sources that essentially host a version of WDS but they host it in its original form and require Java work arounds etc, the link about just seems to work without any work arounds on new browsers and OS's etc

[BTB]

Here’s the horn circuit:-




It’s unheard of that all 4 contacts in the steering wheel behind the airbag fail.

Thanks very much for that!! It looks like the clock spring and/or connections behind the wheel will need a second look. Aren't the 4 switches just the 4 corners behind airbag where ground can make contact and complete the circuit? I agree doesn't seem likely that that is the issue.

[BTB]

The best BMW Wiring Schematics source I have found at the moment short of having and old laptop all setup with outdated versions of Java and with WDS installed is here:
BMW WDS Online (bmwteka.com)

There is some other sources that essentially host a version of WDS but they host it in its original form and require Java work arounds etc, the link about just seems to work without any work arounds on new browsers and OS's etc

That is interesting ... somewhat difficult to navigate but looks like there could be some very valuable stuff in there. Thanks for copying, definitely saving this link.

[Rosie]

Thanks very much for that!! It looks like the clock spring and/or connections behind the wheel will need a second look. Aren't the 4 switches just the 4 corners behind airbag where ground can make contact and complete the circuit? I agree doesn't seem likely that that is the issue.

Yes, they’re part of the plate that the airbag clips into.
There’s a good photo in this recent thread:-

https://nam3forum.com/forums/forum/main-forum/e46-2001-2006/160041-steering-wheel-swap-can-t-get-airbag-to-sit-straight

It may possibly be something as simple as the wire to the plate (RH side in the picture) isn’t attached.

[BTB]

Yes, they’re part of the plate that the airbag clips into.
There’s a good photo in this recent thread:-

https://nam3forum.com/forums/forum/main-forum/e46-2001-2006/160041-steering-wheel-swap-can-t-get-airbag-to-sit-straight

It may possibly be something as simple as the wire to the plate (RH side in the picture) isn’t attached.

That's what I was thinking! I want to just pull the airbag off and take a look around. All other wheel controls work which makes me think the clockspring is ok ... thanks for the input

[BTB]

Hey guys,

I did some more troubleshooting tonight, I think I have all the data I can possibly get in the steering wheel/glovebox area. Please electrical guys let me know if this makes sense and weigh in if you have any input, this issue is bugging the crap out of me and at some point I need to put an aftermarket horn in or maybe wire a button direct to the relay.

I took off the airbag and steering wheel and tested for continuity from the connector behind the clock spring. Clock spring is good, wiring at steering wheel is good (all other steering wheel functions work FYI). At the chassis harness connector that plugs into backside of clockspring I tested for voltage (ignition on); 0 volts on the horn power contact. There are 12 V available on some other contacts and ~2 V on others, didn’t look into what goes to where but the point is the only unpowered device seems to be the horn.

Went back to the glovebox. Fuses 5 and 55 are both powered (both ends of fuses) with ignition on.

Pulled glovebox and looked at horn relay. Pulling the relay and jumping across pins 30 and 87 sounds the horn. Finally, I tested for power at the relay pins. Only pin 30 (power for horn) has power with ignition on. The harness connection at pins 85 and 86 are showing 0 V with ignition on when reference with a ground. Is this right? Shouldn’t the ‘signal’ side of the relay get 12 V all the time, with an open end at the steering wheel so that flow isn’t possible until connection is made back to ground? This makes me believe there must be a break in the circuit between fuse 5 and the relay (red circle below). Can anyone confirm this logic?? I wouldn’t think the wiring between fuse 5 and relay is long at all given they are both in glovebox.

See schematic below. Green items have been checked and shown as functional. I did bench test the relay and get a click and subsequent change in continuity when 12 VDC applied across pins 85/86.





I appreciate the help, thank you gentlemen

-Brendan

[BTB]

Gosh darn it. Please disregard. All this trouble and turns out at one point someone must have snipped the horn line behind fuse 5 to power my gauges when he rewired them … could have sworn the horn just stopped working randomly but it was a while back. Stupid thing, at least I got to learn a thing or two.

Thanks for the help and schematics

[sapote]

Pulled glovebox and looked at horn relay. Pulling the relay and jumping across pins 30 and 87 sounds the horn. Finally, I tested for power at the relay pins. Only pin 30 (power for horn) has power with ignition on. The harness connection at pins 85 and 86 are showing 0 V with ignition on when reference with a ground. Is this right? Shouldn’t the ‘signal’ side of the relay get 12 V all the time, with an open end at the steering wheel so that flow isn’t possible until connection is made back to ground? This makes me believe there must be a break in the circuit between fuse 5 and the relay (red circle below). Can anyone confirm this logic?? I wouldn’t think the wiring between fuse 5 and relay is long at all given they are both in glovebox.

See schematic below. Green items have been checked and shown as functional. I did bench test the relay and get a click and subsequent change in continuity when 12 VDC applied across pins 85/86.

Great that you have fixed it. But it's harder for people to follow when referred to the relay pin numbers while also using the schematic which doesn't have pin85, 86, or any # on the relay.