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Merry Christmas.
Can somebody please give me, or point me to, the troubleshooting steps, for a horn, in an Australian 1990 NA, that won't work

fuse check / connections to horn.

Mr Morlock wrote:fuse check / connections to horn.

Ta Mr Mortlock.
Brake lights working, and the horn is on the same fuse, so safe to say not the fuse?
Took the one connection to the horn off and cleaned it and the slot where it goes into the horn. No go.
Relay? Traced the wire from the horn to, I think, a box with 'Diagnosis' on its lid and a map of things inside that lid. That's where my skill stopped.

I know there is a horn fuse under the steering column to the right.
Or the little wire in the horn button/hub has broken loose (happened to my older steering wheel). Pain to fix as you need to solder it (and a big blob of glue to keep it secure).

Note: solder the wire onto the floating horn plate, blob of glue on wire to stop the wire pulling on the solder connection.

bruce wrote:I know there is a horn fuse under the steering column to the right.
Or the little wire in the horn button/hub has broken loose (happened to my older steering wheel). Pain to fix as you need to solder it (and a big blob of glue to keep it secure).

Yes, one of the two fuse boxes is down low on the right had wall of the footwell.

Just took the rubber shroud off to expose the wires behind the button. Both are on securely, as are the fixed wire on the steering column. (The other is a thicker wire not connected there.)

What am I left with? Relay. Is there one? The horn itself, needs replacing?

OK, after watching Miata University, I am going to buy, when Santa's gone, a testing light. If it lights up when connected to the horn, I will turn the adjuster on the horn and hopefully get a sound.

Most likely the solder blob has come off the boss. take the horn button out and re-solder where it was before.

One way to test a horn is one wire to earth and the other to power e.g. off the car battery. I bet there are plenty of versions on how to check on U tube.

smy0003 wrote:Most likely the solder blob has come off the boss. take the horn button out and re-solder where it was before.

The boss is the little round bit in the middle of the wheel, the bit with the Momo name on it? If so, I don't know how to get that off. But that button clicks, and I've been told, rightly or wrongly, that that is a good sign.

The Boss is Bruce Springsteen.
The boss is the adaptor/section/big chunk behind the steering wheel. You undo the allen key bolts around the Momo button, take off the wheel and what you're left with is the boss. When taking off the wheel the Momo button should be loose. Spade connector on the back of the button, follow that wire and if it falls off, that is your culprit (as it should be soldered onto a plate).

Circuit tester shows that no power is getting to the horn unit itself. So thanks Bruce, will follow your instructions next.

bruce wrote:The Boss is Bruce Springsteen.
The boss is the adaptor/section/big chunk behind the steering wheel. You undo the allen key bolts around the Momo button, take off the wheel and what you're left with is the boss. When taking off the wheel the Momo button should be loose. Spade connector on the back of the button, follow that wire and if it falls off, that is your culprit (as it should be soldered onto a plate).

My little allen key working with one but the others are beyond my tools. I will wait for the auto electricians to return. Oh well, I have learnt a couple of things along the way, so that's good. Thanks all for your help.

They tend to be a bit tight. Mine were loctited in (by paranoid precious owner) so I drilled them out.

After three consultations by an auto electrician, and one new aftermarket horn, the problem, apparently, is an intermittent horn relay. A bash with a hammer hasn't done the trick, so I'm now choosing between used on eBay and new on eBay and Mazda.