DIY: Hooking up the horn to a momo hub

[scorp965]

This is an illustrated write up of how to hook up a horn to a momo (nsx-r type) hub, for use with an aftermarket wheel - as a bit of a disclaimer I am borrowing the wiring diagram for the horn button from the nsxbuilder.com website, which helped me greatly during my install. Prior to starting the momo hub installation I read several writeups here on nsxprime, unfortunatly when it came to the horn most of these writeups ended with "then fabricate something to attach to the back of the momo hub" - having never installed an aftermarket hub before this gave me a bit of pause, although it is exactly what you need to do, the following are pictures of the 'something' I decided to use, and the best part is its using off the shelf parts with no drilling, etc.

This is assuming you already know how to, or have already finished, installing the momo hub, and are looking to install the horn.

The missing link, 1/2" copper tube straps, from home depot:

One such tube strap, in all its glory:

Bent, for use on the car:

This copper tube strap mounts to one of the original screw posts for the cable reel from the OEM wheel, simply take one of the cable reel mounting screws, pass it through the tube strap, and bolt it in place - prior to tightening it down all the way pass an exposed end of a length of wire in between the two ends of the tube strap, like so:

The momo hub is visible on the left, this is the right-most screw post for the OEM cable reel - there is a 12" length of wire sandwiched in the tube strap, and the screw that secures this to the car is tightened down.

Next find your OEM yellow harness, that attached to the original steering wheel - with the other end of your 12" length of wire stick it in pin position #1, as seen in this diagram (from http://www.nsxbuilder.com):

Now, tighten down the nut that secures your momo hub to the car - remember to place the 'turning signal' un-clicker plastic piece in the correct orientation with regards to the hub - once the hub is secured to the car get on your back and look at the back of the hub - ensure your copper tube strap is in contact with the copper ring around the back of the hub - if it is you are 90% complete.

Next you are going to attach the steering wheel to the hub, prior to doing so get yourself another length of wire, this time much smaller (around 4" should be fine) with exposed ends - sandwich one end of this wire between the hub and the steering wheel, and tighten the wheel to the hub, like so (red wire):

The red wire is in contact with the hub, it is your ground - the black wire, built into the hub, is connected to the copper ring around the back of the hub, which is connected to your yellow OEM wiring harness - you connect the two and your horn will beep - wrap one end of the small 4" ground wire around one of the two contacts of your horn button, and attach the black wire built into the momo hub to the other - give the horn button a light push, and it should beep - simply snap the horn button into the aftermarket wheel and you are done.

 

[Sudesh]

Hi,

I'm doing this mod at the moment, I have a genuine momo NSX-R HUB and was doing your copper strap method. I have one problem though, when I fit the HUB and the base touches the copper strap the horn keeps going off! Any suggestions as to where I'm going wrong?

I have one wire coming from the SRS number 1 connector, straight to the copper strap.



EDIT: No need for reply, I managed to work out the problem, The copper strap was touching the HUB as well as the copper base. All sorted now

 

[UnhuZ]

Sudesh, probably your copper strap on the back of the hub, is touching the hub's copper righ and also the hub structure, ence closing the circuit and beep constantly the horn...

Scorp, with this method, isn't there, sometimes or always, a metal scrapping sound as you turn the wheel on your normal driving?? on my previous honda, it did..i had to make a spherical copper thing and lube it to prevent from making the scrapping sound.

excellent writeup, thanks,
Nuno

 

[C-speed]

Great idea! It is indeed a super easy job to hook up the horn.. not sure why most people don't.

Just a suggestion... I'd solder or crimp your wire connections on the button or use a female spade:

and it looks like you need one of these on your copper tube strap connection: :wink:

Ring Terminal:

 

[scorp965]

Sudesh, probably your copper strap on the back of the hub, is touching the hub's copper righ and also the hub structure, ence closing the circuit and beep constantly the horn...

Scorp, with this method, isn't there, sometimes or always, a metal scrapping sound as you turn the wheel on your normal driving?? on my previous honda, it did..i had to make a spherical copper thing and lube it to prevent from making the scrapping sound.

excellent writeup, thanks,
Nuno

I posted this some time ago, when I first did the retrofit (the thread is from Feb 2006), while initially there was no noise, over time, the strap ate through the surface of the copper ring, and developed a slight scraping noise. I sprayed the copper ring with WD40, and it went away, but the next time I had the hub off the car I simply took the long 12" wire, used wire strippers to strip a 1" segment, then used the copper tube strap to hold the wire in place, with the exposed segment in contact with the copper base, rather than make the contact with the solid tube strap.

With only the loose wiring in contact with the hub:

It is not hard enough to slowly grind through the steering wheel, but makes excellent contact. The tube strap is still used, to hold the wire in the exact placement required to make contact, while not falling out of place and coming into direct contact with the hub ring (which causes constant horn) - its critical to place this wire in the middle of the trim ring surface, to avoid this issue, and to make sure the wire itself is snug, as if you're driving and it falls, its a bad situation (you would need to remove your hub to access the contact, but you have a wheel and interior panels to tear off first, while the horn is blaring).

I drove around with this final configuration and my momo hub for around 8 months, with zero further grinding issues, before I recently changed to a non-OEM hub for use with the cable reel, as I needed additional wires for my shift light:

 

[Sudesh]

Hi,

Thanks for the update on your mod and the info on the copper strap and issues on using it over a period of time.

I have now decided to go with a different contact method, something similar but instead using the "Braided brush contacts" from scalextric

These should have a good contact but also not damage the hub base over long periods.

Here is a photo of the contacts: