Wiring in a horn relay...

[pharriso]

When I bought my car it had 2 Hella horns but only 1 horn made any sound. Assuming the issue was the horns I purchased a pair of used Lucas Windtones & renovated them, both are extremely noisy while being bench tested.

When I installed them in the car only one will sound at a time as before... Either the low or the high will work when the other is disconnected. I have renewed & checked both the rack grounding wire & the steering joint wiring jumper, both are good.

I'm thinking that the electrical load is too high for both horns earthing through the column & in particular the horn push contacts. As a solution I propose to add a relay so the horn push is taking a much lower current & will switch the earth circuit per the attached diagram.

Horn_Wiring_WithRelay_1.00.pdf

proposed horn wiring

(31.38 KiB) Downloaded 790 times

I'm no electrical engineer, does this look good to you guys?

[billwill]

Circuit looks OK, though I didn't check the pin numbers on the relay.

[pharriso]

Circuit looks OK, though I didn't check the pin numbers on the relay.

Thanks Bill, I feel safe on the relay terminal numbers thanks to this diagram:

[RotoFlexible]

Phil,

The circuit looks fine, and the relay should make a big difference. However, the fuse block contacts may also limit current to the horns (assuming your car has the same two-fuse arrangement as the S2). When I upgraded my electrics, I provided relays and modern fuses for the horn, high and low beams, heater fan, and electric fuel pump. The horn and headlamp relays get power directly from the battery-alternator (through a big master fuse) rather than through the ignition switch. I try to keep the old Lucas contacts from having to handle too much current where possible. It made a big difference for those high-current items - the heater fan actually works now.

[collins_dan]

Phil, I had the exact experience you had, put in a relay and now both horns work... except when the lights are on. Having now read Andrew's post, I am thinking the fuse box limitations could explain what is happening. Andrew, could you explain more what you did? I would assume you put in a second fuse box, just for those items. Dan

[oldchieft]

Assuming they worked when fitted, then I would try a coat of looking at the pump.

The pump vanes stick, it can be from rust or too thick oil.

Also the gauze filter can be blocked,

Try WD40, running the pump with the pipe off while spraying it in.

The end cover is held with three screws take it off and clean up the vanes on a sheet of wet and dry.

That has always worked for me.

PS also a bit surprised they were not fitted with a relay, worth another check? I always use a feed from un-fused brown and fit an in-line fuse holder.

Jon the Chief

[pharriso]

John... These are Lucas 9H aka Windtone horns... not Air horns...

[RotoFlexible]

Phil, I had the exact experience you had, put in a relay and now both horns work... except when the lights are on. Having now read Andrew's post, I am thinking the fuse box limitations could explain what is happening. Andrew, could you explain more what you did? I would assume you put in a second fuse box, just for those items. Dan

The headlights aren't fed through the fuse box - they are connected directly to the control box (regulator) through the main lamp switch (again, this is for the S2). But if the system is weak, the headlights will pull the whole system down and other components may be affected. The horn actually has sole use of one of the two fuses - the other one handles everything else that's fused.

I built up a separate panel for the fuses and relays, installed behind the dash at the far left.

Trial installation, some fuses not in place.

The headlights are powered through a heavy feed from the starter solenoid through individual fuses and relays. The horn is powered from the same feed and if my wiring diagram is to be believed, I set it up so that power runs out to the horns through the relay and the horns are grounded to the chassis (i.e., the relay is in the hot side of the circuit rather than the ground side - the original arrangement has the horn switch on the ground side of the circuit).

[oldchieft]

John... These are Lucas 9H aka Windtone horns... not Air horns...

Ok, rearrange these words to make a well known phrase or saying.

The stick of end wrong the.

Jon the Chief

[l10tus]

Right, now add in the Air Horns !

Anybody suggest a wiring diagram for both sets of horns, so as to sound at the same time (as original?)

I can only get either or to work ( both with relays)

Any ideas, because that's got to be the follow-on to this thread!

Regards,

Phil.

[oldchieft]

Right, now add in the Air Horns !

Anybody suggest a wiring diagram for both sets of horns, so as to sound at the same time (as original?)

I can only get either or to work ( both with relays)

Any ideas, because that's got to be the follow-on to this thread!

Regards,

Phil.

I had a set up on a Morgan were the electric horn worked off the original switch and another push button operated both horns.

(The electric ones always sounds first as the is no compressor to run up to speed. So it give a quick response followed by a loud blast.)

I will try to remember/work out how I did it. I think it might be by cascading two relays.

Jon the Chief

[billwill]

You don't need anything complicated.

If you already did the relay mod above, just connect the airhorn compressor in parallel with the other horns.

[l10tus]

Bill,

I tried this, but only one set of horns worked at the press of the Horn, seemingly they both need a fair bit of power to run, with only enough available to operate one or the other?

Couldn't get them to both work at the same time!

Can you post a drawing of the correct diagram, showing the both sets of Horns wired to operate through the one, single Horn push, please ?

I like the idea of the Hi- Lo working first, followed by a sustained push, to bring in the air horns aswell!

P.S.
How on earth did the original set up work ? - my car came with both sets of Horns (Hi - Lo and Air Horns) but no second fuse box, relays or extra wiring?? - always been a mystery to me !
Regards,

Phil.

[billwill]

Bill,

I tried this, but only one set of horns worked at the press of the Horn, seemingly they both need a fair bit of power to run, with only enough available to operate one or the other?

Couldn't get them to both work at the same time!

Can you post a drawing of the correct diagram, showing the both sets of Horns wired to operate through the one, single Horn push, please ?

I like the idea of the Hi- Lo working first, followed by a sustained push, to bring in the air horns aswell!

P.S.
How on earth did the original set up work ? - my car came with both sets of Horns (Hi - Lo and Air Horns) but no second fuse box, relays or extra wiring?? - always been a mystery to me !
Regards,

Phil.

>Can you post a drawing of the correct diagram, showing the both sets of Horns wired to operate through the one, single Horn push, please ?

The circuit needed is essentially the same as the one you drew, merely add the air-horn compressor connected to the same two wires as the other two horns. It's just thicker wires you need, I suspect.

Presumably your wires are too thin. I don't recall what type of Elan you have there, but on an S3 (and probably most of the others) the main electric feed is a fairly thick brown wire from the Solenoid to the fusebox. So for your horns I would suggest connecting from that side of the fusebox (test with a voltmeter; it is permanently live with approx 12 volts) then using wire of similar thickness, get an extra fuse box or an in-line fuseholder (fit a 30 amp fuse) and put that in the new thick wire which should then go to the positive of all three horns. Using again thickish wires connect the negative side of all three horns to terminal 30 of the relay and ensure that terminal 87 is connected with a similar thick wire to a very good earthing point.

The activating wires of the relay (pins 85 and 86) and the hornpush in the steering wheel can remain with the existing thin wires as the current there will be small.

~~~~~

Others have said that one of the fuses in the existing two-fuse block is devoted to the horn; if this is the case on your car, you won't need an extra fuse box or inline fuse holder as you can use the existing fuse, but those old Lucas fuse holders are rather crappy, so you should clean the contacts thoroughly and gently squeeze them so that they grip the fuse strongly; use a new 30 amp (?) fuse and check that its contact surfaces are clean.

[gjz30075]

Bill,


P.S.
How on earth did the original set up work ? - my car came with both sets of Horns (Hi - Lo and Air Horns) but no second fuse box, relays or extra wiring?? - always been a mystery to me !
Regards,

Phil.

I agree! I have the same issue as Phil and for now, I'm using a couple of cheapie hi-lo horns from one of
the automotive parts places. Works great, but want to go back to oem. I'm guessing the original horns
work great when new and now, any amount of corrosion in the horns (even though I refurbished mine) is a
roadblock to the necessary electrons