Horn think-think...

[Fingolfin]

I've gotten back into wiring, and have come to the horns (Mog has two Windtone ones). I decided to connect one horn first, and then put the second in, using double female connectors to splice the circuit together, but I haven't gotten past the one horn so far.

These are the things I know:
1) Both horns function. I tested them across the two battery terminals and they made my ears ring.
2) The first horn has power through the purple wire from the fusebox; when connected to just that wire, with the other wire from the horn touching the body, the horn sounds (deafeningly).
3) When the purple/black wire is connected to the horn and, with a length of wire from inside the cabin, to the battery, the horn sounds.
4) The wires in and around the steering column have been badly bodged with dramatically wrong colors, but the wire to do with the horns (that the purple/black connects to) is brown connected to lavender.
5) When connected as I believe it should be, the horn does not sound, nor does my test-light light up across the wires.

Now photos. It looks to me as though the brown plate on the indicator assembly doesn't have any way to make contact with the copper slip ring.[frame][/frame][frame][/frame]

I wonder also, how does the horn make earth? Where does the wire lead? I haven't even gotten into the indicator wiring yet...

[simmitc]

There is a piece missing from the switch. I'm not convinced that it is a genuine switch. There should be a large connector that makes contact with the ring on the column. This is then joined to earth when you press the horn button.

[Fingolfin]

Well, I've never solved a mystery this quickly, but the mystery has both been solved and has deepened. See what you make of this...

The problem with the horn circuit was, as I and Simmitc thought (thanks for that, by the way), the missing contact. However, the contact was there all along -- it was just bent down. Now, as you can see, it's sitting on the slip ring.[frame][/frame]Of course, this contact isn't the one one normally sees here -- usually, as Simmitc said, it's quite a bit larger and heftier. I have a spare one of these larger contacts, which I may change in before finishing this job.
The horns (both connected) now sound properly when the button is depressed, meaning the circuit has been completed. BUT the in-car ammeter shows that the horns draw WAAAAY more current than I thought they ought -- the high-note horn draws about 10 amps while sounding, and the low-note horn draws 15, for a total of 25 amps for both! That's greater than the production of the dynamo, and nearly the threshold for blowing a fuse. Is this normal? What could be wrong if it's not normal?

[Roni]

A relay might be a good idea to protect the slip ring and horn push contacts.
I am at this stage with mine but have a different problem, the steering column is electrically isolated. Head scratching time.

[beero]

They must draw quite a bit of current because the purple and purple/black wires are quite thick compared to most and on mine (62) there is a separate pair of wires for each horn.

[autolycus]

Which model are the horns? There should be a number like WT614 on them somewhere. Even if they're the most powerful type, I don't think one horn should pull 15A, unless they're seriously out of adjustment. Don't just twiddle the adjusters randomly - there are instructions out there.

I'd use a relay for twin horns if I really thought I'd use them more than once a year.

Kevin

[mike.perry]

I have a pair of Lucas Windtones on my Series MM. The wires are heavy duty and are connected with double bullet connectors. They draw a fair amps but not enough to be a problem.
Go to taffthehorn.com website for info on horns

[Fingolfin]

I was unable to find a model number (of course) but this is one of the horns:[frame][/frame]
And this is how I have them connected -- left side is the main loom, right side is horn wiring. I used double connectors so I could have both horns, though only one is connected in this photo.[frame][/frame]
The horn in the shot above is the one that gives a higher note, and it draws 'only' 10 amps. I shall investigate a relay this evening.

[drivewasher]

I don't know how moggie horn is wired, so I'll check in the book. BUT if the steering wheel switch earths the wire from the horn, then BOTH the wires at the horn/loom bullet conectors should have 12 volts (well battery volts) at them with the horn connected as you have it.

[drivewasher]

Just checked the drawing and the steering wheel switch does earth the horn. So unplug the connectors between loom and hord that you show in pic. One wire that comes from the 2 way fuse should have battery volts there. The other wire should go up to the steering wheel switch.

[autolycus]

Here's an article on repairing and adjusting windtones:

http://www.vintagemg.com/ArticlePDFs/THorns1-2.pdf

It seems to confirm that 10A is too high. It's not the effect on the wiring that makes me suggest a relay, but the thought of switching an inductive load of 15-20A and the current through the sliding contact.

Kevin

[Fingolfin]

Drivewasher, yes, that's how it's wired currently -- the purple wire is permanently live, and the purple/black connects to the horn push and is not permanently live. Autolycus, that's a very helpful .pdf...I seem to have two WT618s, as Mog's horns are attached to their baseplates by rivets. I suppose I should attempt to adjust them.

I had the horns lying variously between tests on the ground and the engine bay floor. Could this have affected the reading? It's possible also my ammeter is wrong -- I've obtained a multimeter for the purpose of testing this.

[drivewasher]

The purple / black wire from horn to the push button should be at battery voltage when it's connected to the horn. It's sort of backwards. 12v comes in from the fuse by the purple wire it goes THROUGH the horn windings and up the purple/black wire to the steering column where when you touch purple/black to earth current flows and the horn sounds

To prove this just connect the purple 12v feed to the horn and then short the other horn connection (where the purple/black wire would go) to earth the horn should sound. This wire you put to earth is exactly what the purple/black wire does but it earths it through the horn push in the steering wheel/column.

It actually switches earth and not the battery feed as most switches do

[Fingolfin]

Quite right -- I in fact did short the first horn to earth during installation, via one of the engine mounts, to see that it worked. I'm sorry, Drivewasher, I'm not understanding what you're trying to tell me...the wiring is as you suggested, so far as I can tell. What exactly is your contention?

[Fingolfin]

Additionally, I'm wondering if anyone might have a suggestion as to which relay I might use for the second horn. I've never used a relay before and know rather little about doing so.

[autolycus]

Use the cheapest automotive 4-pin relay you can find - in the UK you could use Item R20B from Vehicle Wiring Products, for instance. Using the standard Bosch terminal numbering convention, your 12v feed could go to terminal 85 and to terminal 30; terminal 86 would then go up to the horn switch; one terminal of each horn would connect to terminal 87, and the other terminals on each horn would connect to earth.

When the horn button is pressed, current flows through the relay coil to earth, the relay is energised, so 30 connects to 87, and the full current drawn by the horns then flows through the relay to the horns and thence to earth. There are other ways of connecting it, but the principle is to ensure that the horn push only switches the small current through the relay coil, not the main current through the horns.

If you want a more period appearance, a 4-terminal Lucas RA4 relay will do the same thing but at a much higher price.

I couldn't quite follow drivewasher's point either, but I'm sure he's right. And I still think that if the horns are pulling that much current, they're not adjusted right. BICBW.

Kevin

[drivewasher]

Fingolfin Sorry just ignore me lol.. I didn't read your post fully and thought you couldn't get the horn to work after finding the "finger" that contacts the slip ring!

[Fingolfin]

Kevin, I did what you suggested -- I ordered that exact relay from VWP, and wired it per your instructions. I wired only one horn, the right one (my standard for one-horn), to test. The horn sounded nicely when I pushed the horn-push, but for no apparent reason ceased functioning entirely after three or four pushes, while the relay still clicks on every push (and the ammeter registers about two or three amps when it clicks). So I dunno what the devil's wrong now...it feels like the horn is burnt out, but how can it be?

I'll take some spare wire and jump from the battery to the horn, see if it sounds. And I have yet to try the other horn.

[Fingolfin]

Well, the right-hand horn definitely seems burnt out; when shorted directly to the battery, it makes no sound greater than a tiny click. The left-hand horn has a puny little whimperish note, nowhere near adequate for motoring. I have no idea what to do.

[mike.perry]

If you remove the cover on the horn there is an adjuster screw which you may be able to tweak to restore the note, otherwise connect the horn directly to the battery terminals to test. I always use my battery charger to test electrical components