VitoCorleone08
New Member
Van failed its MOT last week. Mainly small issues but one of them was that the horn wasn’t working.
Checked the obvious…fuse, relay, the actual horn itself, and all checked out ok. Set about removing the wheel to check the connections at the push ring and click spring and all good there too. There followed a solid afternoon of diagnostic testing with a multimeter and my kingbolen scan tool
By process of elimination, I narrowed the location of the problem to the SAM unit, which for whatever reason wasn’t passing the signal from the horn push to the relay to energise it.
Not wanting to replace the module for the sake of getting the horn blowing (every other function is ok), I set about a workaround for it.
For future Googler purposes, since I couldn’t find anything about this specific issue when I searched for it, here’s the fix process, hopefully help someone out sometime:
you’ll need about 6m of 20amp wire, an inline fuse holder with a 15amp fuse, some male and female spade connectors, some 6mm heat shrink sleeving, and something to use as a cable draw (welding rod, wire coat hanger, something like that).
In the passenger footwell, if you drop the trim panel, you’ll see the wiring grommets through the firewall into the fuse box. Draw a couple of wires through and run them up behind the dash into the steering column - airbag, wheel and clock spring need to be removed, so disconnect the ground lead of the battery first! Cut the black and brown wires on the back of the clock spring connector plug leaving enough tail on the wires to crimp your new wires onto. Cap off the cut ends of the existing wires with insulation or heat shrink. Check you have continuity on both wires at the fuse box end and then you’re done at the steering wheel, so you can put it all back together.
At the fuse box end, pull out your existing horn relay…you’ll be reusing it shortly. One of your new wires will need to be suitably earthed to the metalwork - I ran mine out of the grommet on the left of the box and crimped a ring terminal on the end, then used the fuse box bracket bolt at the chassis rail to earth it (clean up the bolt first…it’ll be minging!). The other will go to pin 85 on your relay- that’ll be the activation wire from the push. Pins 30 & 86 on your relay will need to be joined into a spade connector and connected to one side of your new fuse holder. The other side of the fuse holder wire will need a male spade connector crimped on, and will go to a switched 12v supply - there are loads on the bus strip down the left side of the fuse box so identify one with a meter and plug in.
Pin 87 on the relay goes out to the horn, which is already connected to pin 30 on the relay socket of the fuse box, so make up a jumper wire from the relay to the socket and plug in.
Reconnect the battery ground, switch on the ignition, and if all your components are good and everything is wired correctly, give the airbag a push and you should have a horn
Once you’re happy it’s all functioning, heat shrink your connections and you’re good to go
Checked the obvious…fuse, relay, the actual horn itself, and all checked out ok. Set about removing the wheel to check the connections at the push ring and click spring and all good there too. There followed a solid afternoon of diagnostic testing with a multimeter and my kingbolen scan tool
By process of elimination, I narrowed the location of the problem to the SAM unit, which for whatever reason wasn’t passing the signal from the horn push to the relay to energise it.
Not wanting to replace the module for the sake of getting the horn blowing (every other function is ok), I set about a workaround for it.
For future Googler purposes, since I couldn’t find anything about this specific issue when I searched for it, here’s the fix process, hopefully help someone out sometime:
you’ll need about 6m of 20amp wire, an inline fuse holder with a 15amp fuse, some male and female spade connectors, some 6mm heat shrink sleeving, and something to use as a cable draw (welding rod, wire coat hanger, something like that).
In the passenger footwell, if you drop the trim panel, you’ll see the wiring grommets through the firewall into the fuse box. Draw a couple of wires through and run them up behind the dash into the steering column - airbag, wheel and clock spring need to be removed, so disconnect the ground lead of the battery first! Cut the black and brown wires on the back of the clock spring connector plug leaving enough tail on the wires to crimp your new wires onto. Cap off the cut ends of the existing wires with insulation or heat shrink. Check you have continuity on both wires at the fuse box end and then you’re done at the steering wheel, so you can put it all back together.
At the fuse box end, pull out your existing horn relay…you’ll be reusing it shortly. One of your new wires will need to be suitably earthed to the metalwork - I ran mine out of the grommet on the left of the box and crimped a ring terminal on the end, then used the fuse box bracket bolt at the chassis rail to earth it (clean up the bolt first…it’ll be minging!). The other will go to pin 85 on your relay- that’ll be the activation wire from the push. Pins 30 & 86 on your relay will need to be joined into a spade connector and connected to one side of your new fuse holder. The other side of the fuse holder wire will need a male spade connector crimped on, and will go to a switched 12v supply - there are loads on the bus strip down the left side of the fuse box so identify one with a meter and plug in.
Pin 87 on the relay goes out to the horn, which is already connected to pin 30 on the relay socket of the fuse box, so make up a jumper wire from the relay to the socket and plug in.
Reconnect the battery ground, switch on the ignition, and if all your components are good and everything is wired correctly, give the airbag a push and you should have a horn
Once you’re happy it’s all functioning, heat shrink your connections and you’re good to go
