Horn wiring, a little bit different

Post by **d_harris** » Mon May 25, 2009 10:33 pm

I'm thinking of security measures here and a makeshift alarm, is there an easy way that when the ignition is turned on that the horn can sound unless a switch is flicked........

It'd also be good if it stays on until a reset switch somewhere is hit....

Post by **d_harris** » Mon May 25, 2009 11:12 pm

Having taken a quick look at the wiring diagram I guess it would be best to take a feed off the blue wire?

Post by **bpr81a** » Mon May 25, 2009 11:21 pm

You're going to need a relay - the horn is permanently connected to live, and is earthed to the column when you press the button.

Post by **d_harris** » Mon May 25, 2009 11:45 pm

Not mine, at the moment its not connected to anything and I don't have a centre horn push so its going switched live

Problem is how to wire said relay....

Post by **bmcecosse** » Tue May 26, 2009 10:07 am

Would work best if that horn (or siren) is INSIDE the car - so anyone trying to steal it will be so deafened they won't be able to stay inside the car ! Obviously need to be somehwere where it can't just easily be disabled - or ripped out. Wouldn't worry abot relay - it's not something that's going to be used very often.

Post by **Alec** » Tue May 26, 2009 5:38 pm

Hello Dan,

it will be a fairly simple circuit, you will need a relay if you want to be able to latch it in.

The relay coil is connected to an ignition fed source and then through your enable switch with the other side earthed of course.Connect the relay contact to a permanent live (purple is the normal colour for such a feed) The other side of the contact feeds the horn and also connects to the ignition side connection of the enable switch. (If you wish to use the standard wiring for the horn then a double pole relay will be required with one pole doing the relay latch function and the other connected to the horn 'live' and earth.

With your enable switch made, i.e. the system is armed, switching on the ignition will bring in the relay and sound the horn. Simply switching off the ignition will not drop out the relay because it is now being fed from the relay contact. This will keep blowing until the 'enable' switch is opened.

If the description is confusing, drop me a pm and I'll send you a diagram. It is simpler than it sounds:-)

Alec

Post by **Alec** » Tue May 26, 2009 7:05 pm

Hello all,

"The relay coil is connected to an ignition fed source and then through your enable switch "

I've realised that is not quite right and the two switches should be in parallel not series then connecting to the relay coil.

Alec

Post by **bmcecosse** » Tue May 26, 2009 11:07 pm

If fed from the purple wire - all they would have to do is pull the fuse! Better to get feed from the brown wire - and have an 'in-line' fuse somewhere out of sight.

Post by **Jefftav** » Wed May 27, 2009 8:25 am

Hi Alec, Any chance of a diagram? Jeff

Post by **Alec** » Wed May 27, 2009 11:35 am

Hello Jeff,

no problem, would you drop me a pm with your e-mail address on and i will send it to you.

BMCE, yes that's true but nothing is invincible if the 'villain' knows his wiring, a combination of things is probably best as it would take time to defeat, i.e the hidden fuel pump switch. (Or as I have on my Triumph a fuel tap in the boot.)

Alec

Post by **bmcecosse** » Wed May 27, 2009 3:17 pm

Agreed - it's just the natural instinct would be to pull the fuses out - if that stops the noise then they can continue with their evil plan! Of course - they can just take the battery lead off (probably need a spanner for that) which will stop everything - unless a secret SAB (stand alone battery) is installed (as in burglar alarm systems) to keep the horn blasting away anyway!!