About to try repairing horns

[Gebbly]

On my e86 Z4M the horns dont work. When pressing the steering wheel I can hear a click from behind the glove box which makes me think the signal may be getting at least as far as the relay.
As a start to my Z4M ownership journey I have now bought some low profile ramps, a low profile jack, some jack stands, wheel chocks and some jack point rubber pads (I have seen mangled jack points before).
As [ref]enuff_zed[/ref] suggests in another thread the first thing I will try is replacing the horns as [ref]umfaan[/ref] happened to be selling a pair on here the other day.

I plan to follow the guide at https://www.youtube.com/watch?v=sELrm_yYQCg to lift the car. Then remove one front wheel, remove the arch liner and connect a replacement horn into the connector to see if that works. If it works I will put the arch liner and wheel back and then try the other side.

I would be grateful for any advice, warnings, tips about this process please.

As a starter, is there a specific torque that should be applied when attaching wheel nuts to a wheel hub when reinstalling the wheel?

 

[enuff_zed]

 

[Gebbly]

Brilliant, thanks [ref]enuff_zed[/ref]

 

[Gebbly]

If I want to test the horns with a DC power supply does anyone know if it matters which pin I connect to 12v and which to neutral? If it does matter does anyone know which is which?

 

[enuff_zed]

If I want to test the horns with a DC power supply does anyone know if it matters which pin I connect to 12v and which to neutral? If it does matter does anyone know which is which?

doesn’t matter

 

[Zedebee]

Then remove one front wheel, remove the arch liner and connect a replacement horn into the connector to see if that works.

You don’t need to remove the whole arch liner, just the lower of the two removable panels.

You don’t actually need to jack up the car or remove the wheel either (just turn the steering to full lock), although you will have much better access if you do.

 

[Gebbly]

Thanks, I'll try by the access panels first. I have seen the pictures others have posted that it has 2 tabs which rotate to release it. But it looks like quite an awkward position. Maybe I'll just see what access is like via the panels tonight in prep for doing the fix this weekend.

I have tested one of the horns from umfaan with my DC power supply and its working. Didnt half make me jump when it went off in my lap

 

[Gebbly]

I tried gaining access via the lower panel but it wouldnt budge. I turned the 2 plastic clips through 180 degrees but couldnt get it out. There is a flap to the side that is slotted into the surrounding plastic and also the whole piece feels like it is also attached to the plastic in another direction. In the photos below you can see what it looks like from inside the wheel arch and the second photo shows the plastic that it is attached to, the whole "tunnel" piece of plastic.



I'm a bit concerned about trying to remove the arch liner if it is attached to that tunnel piece of plastic.

 

[enuff_zed]

I tried gaining access via the lower panel but it wouldnt budge. I turned the 2 plastic clips through 180 degrees but couldnt get it out. There is a flap to the side that is slotted into the surrounding plastic and also the whole piece feels like it is also attached to the plastic in another direction. In the photos below you can see what it looks like from inside the wheel arch and the second photo shows the plastic that it is attached to, the whole "tunnel" piece of plastic.
lowerPanelInside.jpg
lowerPanelOutside.jpg

I'm a bit concerned about trying to remove the arch liner if it is attached to that tunnel piece of plastic.

Ah ha! I think we'd all missed that it's an M bumper. Usually that lower flap would give access to the fog lights, but yours is a cooling duct instead.

 

[Gebbly]

So the access panel wont give me access to anything? Oh bum!
If I attempt to remove the wheel arch liner will that remove that cooling duct with it or is it more complicated than that? Is getting to the horns in a M a different procedure entirely?

 

[Gebbly]

This looks like a pretty thorough guide
https://www.pelicanparts.com/techarticles/BMW_Z4M/130-BODY-Wheel_Well_Liner_Replacement/130-BODY-Wheel_Well_Liner_Replacement.htm
and they seem to have the plastic duct too. If its sunny tomorrow I'll try this.

 

[Umfaan]

Pelican is an always a great guide

 

[Dubbedown]

It’s off to the side closer to the oil cooler. Take off the larger access panel if possible. Else you’ll need to take the wheel and wheel liner off, or conversely the front bumper. I snapped this when I did my splitter install but there’s one on each side (high and low).

 

[Gebbly]

Thanks for the excellent photo [ref]Dubbedown[/ref]. That helps a lot. Snapping a body panel is scary so I will try removing the wheel and arch liner and try and do it that way. I've been procrastinating putting it off as its the first serious maintenance job I have undertaken on the car. I spent all morning looking for my torque wrench. Finally found it along with another old set of jack and jack stands so now I have 2 sets. Anyone need a set of 2 ton jack, jack stands and chocks?
Tomorrow, definitely tomorrow...

 

[Dubbedown]

Thanks for the excellent photo [ref]Dubbedown[/ref]. That helps a lot. Snapping a body panel is scary so I will try removing the wheel and arch liner and try and do it that way. I've been procrastinating putting it off as its the first serious maintenance job I have undertaken on the car. I spent all morning looking for my torque wrench. Finally found it along with another old set of jack and jack stands so now I have 2 sets. Anyone need a set of 2 ton jack, jack stands and chocks?
Tomorrow, definitely tomorrow...

I just realized you won’t be able to remove the large access panel because that’s where the brake duct is normally secured to. In my photo, I deleted the brake ducts, which would normally be hanging where that splitter support rod is. So I think removing the wheel liner is your best bet.

 

[Gebbly]

I'm following the approach of jacking the car up and removing the arch liner.

N/S horn replaced and now working. [ref]enuff_zed[/ref] was absolutely right when he said it was probably the actual horns. I'm hoping that if the n/s is now working it means all the wiring is ok and the o/s will work once I replace that horn. Taking a breather after the first one though, phew.

Hardest parts so far were convincing the wheel to come off, took some gentle persuasion with a rubber mallet and harder still refitting the arch liner and lining up all the holes. Actual horn replacement, once I had access, was a piece of cake.

Lunch break then round 2, the o/s....

 

[Gebbly]

Second horn replaced and both working now. I found that if I removed the nuts holding the front half of the arch liner and left the rear alone I was able to move the arch liner enough to reach in and swap out the horn, so it is possible to do the horn swap without completely removing the liner.

I now have 2 old horns. Is it possible to take them apart to refurb and reuse or do I just have to bin them?

Also, I really dislike those stupid plastic expanding screw things. They are a sod to remove.

 

[enuff_zed]

I now have 2 old horns. Is it possible to take them apart to refurb and reuse or do I just have to bin them?

Don't think they are rare enough to bother saving tbh.