6 replies to this topic

[Spitz]

My MkI has undergone some "re-wiring" by the PO...and as a result has no horn fitted, or steering wheel centre push etc.

 

I'd like to install a horn with a switch on the dash or somewhere else handy....just not a steeering wheel centre push. ( which reminds me, I need to find a switch that will work for a horn)

 

So.....if I fit a horn with a relay, where can I get a 12V feed?  This is a floor start car.  Can I just run a wire from the "input" side of one of the fuse box terminals?

[ChopperHarris]

Just a pointer, I think MK1 horns were permanently live and the switch made the earth (through the column)

[dklawson]

Matthew, ChopperHarris is correct.  The Mk1 horn did not use a relay and was permanently "hot" with the horn push providing a ground/earth path.

 

You should be able to find a generic dash mounted horn push button at a larger auto parts store.  They were very common in the 1970s... not so much today.

 

At the slam panel in the front of the car you need to look for two wires, a purple wire and a purple/black wire.  The purple wire (if still connected on the far end) will be a permanently hot supply to one side of the horn.  The purple black should go off to the interior of the car and is normally run up the steering column under the shroud to the slip ring behind the steering wheel.  To use your aftermarket switch, the purple/black wire at the slam panel is connected to the second horn terminal and when the end in the car is earthed, the horn will sound.  For the aftermarket switch you would connect the purple/black to one switch terminal and a black earth wire to the other horn terminal.  That's the basic wiring without a relay.

 

If you want to add the relay, buy a generic Bosch/ISO 30A or 40A relay at the parts store.  The purple and purple black wires would be connected to the relay coil's terminals.  For power you would then run a fused wire from the solenoid or fuse box to one of the relay's power terminals.  The other relay power terminal would need a wire run to a horn terminal and finally the remaining horn terminal is connected to earth/ground.

[Spitz]

Thanks both.

 

Reason for the relay is it comes with a horn kit I've found on sale (air).

My wires up front are original cloth, and the insulation inside is faded and not recognisable.

I like the idea of a relay actually…..If it's night time, lights on, brakes on, maybe indicator on, then horn on….lots of amps

 

Also...the wire from the horn centre push ( on the signal assemble ) is brown with black tracer

Edited by Spitz, 22 June 2015 - 07:27 PM.

[dklawson]

Maybe that center wire just looks brown with a black tracer.  I know it was very discolored on my car.

 

I could never make the horn in my Mk1 work UNTIL I added the relay.  The regular horn button actuates the relay which in turn operates the horn.  For some reason even after cleaning all the contacts, slip ring, and horn push there was still too much resistance to operate the horn directly from the horn push button.  

 

The Bosch/ISO relays you find at the parts store (or eBay) are great for this.  They are readily available and not too expensive.  On eBay you will often find sellers who include pre-wired relay sockets/bases for the relays.  That makes wiring cleaner and future relay replacement easier.

[ChopperHarris]

Spitz...the relay makes no difference to what other electrical items are on.

It just takes the amps off a push switch which is susceptible to arcing, and saves having heavy gauge wire up to the switch

[Spitz]

It's definately brown/black Doug.  It's a brand new indicator stalk (new wire)...and the wire under the dash is same colour ( 1962 by the way )

Edited by Spitz, 22 June 2015 - 08:56 PM.