4 pin relay woes

[caduceus]

A question/problem for those who know about auto electrics/electrics.
My little runaround needs a new hooter so I bought a two tone type online. I've followed the instructions to the tee and it won't work. The relay clicks when I press the horn but no sound. I've tested them from the battery and they both work.
Does this sound right (as I have looked at YT videos and some conflict with this):

Pin No85 = +ve from dash/horn press.
Pin No 86 linked to Pin No 30.
Pin No 30 is a fused (10amp) feed from the battery.
Pin No 87 goes to the +ve on the new horns, which are linked.
-ve on both horns go to earth.

Any help appreciated. Thanks.

Regards
Cad

[sunbeam alpine]

caduceus said:

A question/problem for those who know about auto electrics/electrics.
My little runaround needs a new hooter so I bought a two tone type online. I've followed the instructions to the tee and it won't work. The relay clicks when I press the horn but no sound. I've tested them from the battery and they both work.
Does this sound right (as I have looked at YT videos and some conflict with this):

Pin No85 = +ve from dash/horn press.
Pin No 86 linked to Pin No 30.
Pin No 30 is a fused (10amp) feed from the battery.
Pin No 87 goes to the +ve on the new horns, which are linked.
-ve on both horns go to earth.

Any help appreciated. Thanks.

Regards
Cad

Normally it should be

Pin No85 = earth/chassis ground
Pin No 86 +ve from dash/horn press
Pin No 30 is a fused (10amp) feed from the battery.
Pin No 87 goes to the +ve on the new horns, which are linked

[littleredrooster]

I'm sure that more than one of my previous cars/bikes had the horn wired as a switched live, with the horn button sending it to earth to complete the circuit. This means that only one wire goes to the button.

If that's the case with yours, what you think is live may well be earth. Sorry I can't figure the alternative wiring out, though.

[s p a c e m a n]

Did the car not originally have a horn? I've always just used those wires, quick snip and some connectors and then cable tie the trumpets under the bumper

[caduceus]

Thanks for the replies gentlemen.

Sunbeam - I've tried your alternate wiring. Same response...doesn't work. Blows the cars 10amp fuse in the fuse box, but not the inline 10amp fuse feed from battery.

[caduceus]

Rooster & Space - the car did have a horn. It had one wire going to it. It was a pathetic little moped type, embarrassing to use.
The one connection theory does link up with your theory Rooster.

[sunbeam alpine]

caduceus said:

Thanks for the replies gentlemen.

Sunbeam - I've tried your alternate wiring. Same response...doesn't work. Blows the cars 10amp fuse in the fuse box, but not the inline 10amp fuse feed from battery.

If what others have said is correct, you just need to swap the connections so that 86 goes to ground and 85 goes to the horn switch.

[caduceus]

Yup, just tried that. No horn blow and the cars 10amp fuse blows.
I think this isn't going to be as straight forward as it should be.

[LordLoveLength]

The way you had it wired originally sounds like it should work as long as the horn push connects to ground when pushed.
Do the horns work when wired direct to the battery? What current are they rated at?
Could e a faulty relay also.

[caduceus]

LordLoveLength said:

The way you had it wired originally sounds like it should work as long as the horn push connects to ground when pushed.
Do the horns work when wired direct to the battery? What current are they rated at?
Could e a faulty relay also.

Yes, I've tested the horns direct and they work. Not sure what rating they are though, as it doesn't say on the box. E11 and 28R are stamped into the horns. Low tone is 410htz and high is 510htz.
I bought another relay also, so two can't be bad.
It should be so simple, I mean it's just a switch.

[LordLoveLength]

Are you sure the horn ground is good?
Try swapping the horns for a 21W bulb - does it light when you press the horn button? Can you hear the relay click?
It could be a poor ground or supply - the bulb may glow dimly if there is.

Edited by LordLoveLength on Saturday 10th June 15:46

[ARHarh]

I think before you do anything you need to establish if the horn button is switching Gnd or Positive, until then you are only going to create smoke or flashes

[caduceus]

LordLoveLength said:

Are you sure the horn ground is good?
Try swapping the horns for a 21W bulb - does it light when you press the horn button? Can you hear the relay click?
It could be a poor ground or supply - the bulb may glow dimly if there is.

Edited by LordLoveLength on Saturday 10th June 15:46

I've made links from the ground on the body which the battery neg connects to. I assumed that would be good. But I'll check the tightness.

[caduceus]

ARHarh said:

I think before you do anything you need to establish if the horn button is switching Gnd or Positive, until then you are only going to create smoke or flashes

How do I do that? I've pressed the horn and put a meter on it. It shows 12v, if that's what you mean.

[ARHarh]

Disconnect the battery or take out the horn fuse. Set meter to resistance. Connect meter wire to the wire from the horn switch. Put other meter wire to ground. Press button and see if the resistance goes to 0 or nearly 0. If it does it's switching ground, if not it's switching live. If smoke comes out you have got something still connected to live. I always thought horns were switched down to ground. But not played with one on anything new than the 1970s and Lucas really was not the best example to base your car electrics knowledge on

[kabman]

caduceus said:

Pin No85 = +ve from dash/horn press.
Pin No 86 linked to Pin No 30.
Pin No 30 is a fused (10amp) feed from the battery.
Pin No 87 goes to the +ve on the new horns, which are linked.
-ve on both horns go to earth.

This would work if your horn button switched to ground. But since it switches power, the control side of the relay has no ground. Change terminal 86 to a ground (remove the link to pin 30 obviously) and it will work.

[caduceus]

kabman said:

caduceus said:

Pin No85 = +ve from dash/horn press.
Pin No 86 linked to Pin No 30.
Pin No 30 is a fused (10amp) feed from the battery.
Pin No 87 goes to the +ve on the new horns, which are linked.
-ve on both horns go to earth.

This would work if your horn button switched to ground. But since it switches power, the control side of the relay has no ground. Change terminal 86 to a ground (remove the link to pin 30 obviously) and it will work.

I have...it doesn't

[caduceus]

ARHarh said:

Disconnect the battery or take out the horn fuse. Set meter to resistance. Connect meter wire to the wire from the horn switch. Put other meter wire to ground. Press button and see if the resistance goes to 0 or nearly 0. If it does it's switching ground, if not it's switching live. If smoke comes out you have got something still connected to live. I always thought horns were switched down to ground. But not played with one on anything new than the 1970s and Lucas really was not the best example to base your car electrics knowledge on

I'll give that a go next.

[caduceus]

Tried that. It gave the same result as if you were testing a blown fuse. It didn't go to 0. It stayed silent and meter showed 0L.

[ARHarh]

Sounds like it is switching live then.