how do i wire a 5 pin relay for my corsa steering

[mirpur]

my horn set up works by earthing the switch, i have changed my steering and need to put in a 5 pin relay to activate the horn,anyone have any idea how to wire in a 5 pin relay on a horn system which earths when the switch is pressed so that the horn sounds

[Andy K]

tell us what you have done

Have you removed an airbag ?

What wheel have you fitted ?

[mirpur]

its a cav mk2 so has the pin which earths as you press the steering horn, i have taken this steering off and put on a airbag steering with a squibb on the back, i need to connect the wires of the squibb through a 5 pin relay so that the relay earths and causes the horn to sound, airbag does not have to be connected

[MSG]

You just need to have a positive 12V to one side of the relay coil say pin 86, and the other side of the coil pin 85 then gets earthed through your steering horn button, this brings the relay on when you press on the horn button, then you switch a fused +12V via the relay contacts, so let us say you apply a +12 to contact pin 30 then this will bridge the contact to pin 87 completing the circuit and you get +12v out at pin 87 that then feeds the horn +ve and the horn is negative earthed to car body.

The only thing you will need to decide is if you want your horn to work with the ignition on or any time even when the ignition is off, so you will need a +12v to the relay coil (pin 86) from the source that is either switched on by the ignition switch or a source that is permanently live even when the ignition switch is off, and for safety this should also be fused source if possible,

but the horn power source (+12V) ( pin 30) should be seperately fused as horns can draw a lot of current like say 10amps so this source again is your choice as you may be able to use an existing fuse that was already designed in the car for the horn application, however this existing fused circuit may be switched circuit via the ignition switch, in which case the horn won't work when the keys are out.


In my view a horn should always be responsive even when the ignition is off, as an emergency warning device to altert passers by, like if someone locks kids in a car and promised to return in 5 minutes and doesn't then the kids can alert passers by, long while ago, my father had pulled behind a lorry and the driver of the lorry was not aware, my dad had left us alone in the car and the lorry driver started to reverse, he could not have seen us, so i immidiately pressed on the button and my dad's good old Hillman brought that lorry driver to attention and he stopped! imagine if the horn only worked on the ignition then I would have been long squashed like a lemon!!

( for simplicity you can also wire the +12V fused source to both pins 30 and pin 86, so in all you will use 3 wires, )

[mirpur]

msg the explanation you have given is it for a horn which works by being earthed

[Andy K]

I take your point MSG, but its too much effort to change on a mk2 cav

So

Pin 86 a + feed (say the wiper/horn fuse)
Pin 85 airbag horn brown wire
pin 30 earth
pin 87 the cavs origional horn wire brown/white

you will also need the earth the other airbag wheels brown wire

[MSG]

what Mirpur asked was for a relay arrangement that is tripped by a steering horn button that gets earthed, so the relay must have a positive to its coil all the time, and when the contacts close it switches a positive 12v to the horn which gets its earth from the car's earthed metal parts where it is mounted.

so yes mirpur the relay would trip when you press horn button earthing one side of the relay coil and the horn will get a 12v positive feed , you may try andy's suggestion if you want.

[mirpur]

thanks for the info, andy the steering has two wires for each horn, ie brown and brown and white do these both go to pin 85 or only one to pin 85 and the other earthed, if this is the case which goes where

[MSG]

In my opinion both should go to the same pin on the relay because if you must have got two seperate buttons one on left and one on right, unlike some steering wheels have one single button in the middle.

(Just make sure you know that both the Brown or Brown/white wires are is related to horn button/buttons, and is not part of the air bag.)

Do not connect any part of the air bag system to the relay.

[mirpur]

air bag is disconnected from behind as the cav mk2 never had airbag or sensors to activate it

[MSG]

so you don't have any worries in case the air bag malfunctions due to using incorrect wires, so just check that each time you press the horn button then the corresponding wire from each of those buttons is earthed using a multimeter. And if they do you can connect both of them together to the relau coil pin 85 .

[Andy K]

my horn set up works by earthing the switch

Mk2 Cavs have a constant ignition supply to the horn
and switch the earth via the steering wheel control (as pointed out above)

thanks for the info, andy the steering has two wires for each horn, ie brown and brown and white
one to pin 85 and the other earthed, if this is the case which goes where

Yes one to the relay 85 and one to earth. Doesn't matter which way round.

[mirpur]

cheers will give it a go tomorrow

[mirpur]

cheers all sorted thanks for the advice used andys wiring diagram and all went well thankyou msg for your input