Sit in the car, turn the ignition to position 1 and press the horn button a few times.
Obviously if you are reading this your horn won't be making a noise but we aren't listening for that. Each time you press the horn, listen for a click coming from underneath the dashboard. This
tells you that the relay inside the fuse box is OK. As long as you can hear the clicking you are
OK to continue, if not then you are gonna have a fun weekend trying to make it work.
Gaining access to the Roadster horn is a lot easier than on the fortwo.
Remove the front plastic boot liner insert, this can be seen here.
Look on the right hand side and you will see the horn.
Pull the connections from the horn and clean them with WD40, switch cleaner or emery paper.
Dab both terminals with copper grease and reattach the connections.
This will stop the ingress of contamination again and should stop them breaking again.
Replacing With OEM
Go to smart and order part number SQ0016058V00100000 which is labled on the smart
system as 'De-Zweiklanghor' which means 'The Twin Horn'. They cost about £25.
Remove the old horn by undoing the torx bolt at the top, notice how the strap has a tab
on the end that goes into the bodywork to secure it. The new horn has one strap the
same, the second strap has a straight tab. This sits against the bodywork and the
hooked tab strap goes over the top to lock them both in place.
With the new horns bolted in place, use the new wiring connection to join the old wiring to
the horns. It is worth dabbing each contact with copper grease to protect the connection.
Test the horn works OK and replace the boot liner. Job done.
Replacing With Aftermarket
Very simple, buy a new (loud) single horn and fit it as a replacement to the one you removed.
A popular replacement is the Stebel Nautilus or Euroblast. Watch out for poor copies though.
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