Using steering wheel switch to operate air horns
In order to use the stock switch with the air horns, a simple circuit
is necessary in order to have the stock alarm work as intended.
The problem is that if we disconnect the stock horns and wire them
to drive the air horns the stock alarm does not perform as intended.
When the alarm goes off the air horns can not react fast enough and
therefore no sound is emitted. The trick is to get the stock switch to
drive the stock horns when the ignition is off (i.e. the car parked)
and to drive the air horns when running (i.e. driving down the road).
If you have an aftermarket alarm this write up may not apply.
Here is a list of the items required:
15-20 Female spade connectors (light blue)
20 GA stranded wire (about 4 ft)
1 single throw single pole relay STSP referred to as k2 in my shcematic (usually this relay comes
with the air horns kit) about 15-20 amps rated.
1 single throw double pole relay STDP referred to as k1 in my shcematic (readily available from
any autostore) 5-10 amps rated.
1 fuse connector
1 15-20A fuse
Crimping tool
NOTE: Make sure the relays have their internal schematics printed on
the side
Print my schematics/sketches shown on a separate page on my site.
Procedure:
1. Determine how and where to physically mount your relays. Refer to my Relay Mounting
(Installation) for a sketch on how and where I mounted my relays. I used and L shaped bracket
and mounted the relays back to back, i then installed the assembly to the chassis
right behind the driver's side headlamp.
2. Disconnect the connectors (female made out of rubber) to both stock horns,
you can get to the horns by removing the front amber lights and looking through
the openings with a flashlight.
3. Run wires w1 & w2 from each of your stock horns to the normally closed
pin (N.C.) of k1, at this pin both wires must make contact,
crimp them to one connector and install them to the relay. Crimp a connector to
the other end of the wires (one each) and install/wire to the stock horns.
4. Now you need to choose one of the two original connectors (one of
two you disconnected in step 2 above) and run wire w3 from it to the
wiper pin of k1 (the other stock connector is not used and you
can just tape it up and put it to the side). Crimp a male spade
connector to one end of the w3 wire (the end closest to the stock
connector) and insert itinto the stock female connector.
Use electric tape to ensure this connection doesn't shake loose with
time.
5. This is a good testing point. Electrically you have done nothing
so far. The stock switch is still driving the stock horns weather the
ignition is on or off. To test simply press on the stock switch, both
stock horns must sound, if they don't something is not wired properly.
6. Now you need run wire w4 from a voltage source that only comes one when the
ignition is on, make sure the source does not come on when the stock alrm goes off
(I ran a wire from the cigaret lighter through the
fire wall and used it as my source. Other people use the fusible links).
7. Run wire w5 from ground to the coil pin of k1.
8. Run wire w4 from your switched source to the other pin of the coil of k1.
9. Here is another good testing point. When the ignition is off
and you depress the horn switch the stock horns should sound; as soon
as you turn the ignition on and depress the switch there should be no
sound (the stock horns have been completely disabled).
10. If you have passed the two tests above you are now ready to run wire
w6 from the N.O. of k1 to one of the coil pins of k2.
11. Now is time to wire you air horns (some of you already have them
wired).
12. The compressor of the air horns requires 10-15 Amps, hence it is
better to use relay k2 to drive it.
13. Run a wire from the battery to your fuse connector.
14. Run wire w7 from the other wire of the fuse connector to the
N.O. pin of k2.
15. Run wire w8 from the wiper of k2 to the air compressor (wire
the compressor as indicated by the instructions that came with it).
16. Run wire w9 from ground to one of the pins of the coil of k2.
17. Run a wire from the N.O. pin of k1 (the one you
installed first) to the other coil pin of the STSP relay (the one
that actually drives the compressor).
Theoretically this is all there is to it. All we are really doing
with this circuit is re-routing the path the stock switch takes
when the ignition is on.
Please note that this is the procedure I used and it seems to work well.
You are using this intructions at your own risk.