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MG Midget and Sprite Technical - The horns of a dilemma

Today I spent 2 hours trying to find out why the horn button stopped working. I traced the wiring right back, and found the steering column no longer provides an earth. I always wondered how it ever could, but I traditionally tested the horns by shorting between the contact pencil and the column. Now that test fails every time. I even tried connecting a wire between the steering rack and the chassis - no joy.

I have air horns and a relay, and they all work fine when the button is shorted out. Have I misunderstood how this is supposed to work?

Les
L B Rose

Many people have had to earth the column, particularly if you are using a rebuilt rack. I just used a spare engine earthing strap I had knocking about.

Also check the wire inside the contact pencil. It often works as a fuse!...
Clive Seager

Yes, I have had to earth the column on my MGB.
Mike Howlett

But how to connect the rotating column to the stationary chassis?
L B Rose

Back up for a moment and analyze the situation: it worked, then it didn't work so something has changed (sorry to be stating the obvious). You can temporarily attach a wire from the column to the chassis just to create an electrical circuit for troubleshooting purposes but my guess would be it is somewhere in the button mechanism & all those little parts. I would remove the battery connection and use an ohm meter to test for continuity one item at a time. Time consuming? yes, but the only way to eliminate each item in the chain of events. Usually the part that moves the most is the most likely to fail, I would definitely investigate the horn brush (part # 560-430 in the Moss catalog) as Clive stated, it works like a fuse and the little braided wire will flex itself to death over time. Good luck!
Stan Kowznofski

From previous threads I remember that there are different lengths of horn push brush and from JT No.1 vid that the sprung end of the horn push brush goes in first/towards the engine.
Nigel Atkins

I made a wrap-over earth for the column

made from brass rod, it mounts on one end to the inner wing using a loop under a bolt head, the other end is a J that hooks over the steering shaft.

To make sure there is a good contact clean the paint from the shaft at the point of contact.

the other way is to loop the earthing strap around the lower column. I did that first but the safety inspector didn't like it.
Dominic Clancy

Les I didn't need to put the earth wire on a rotating part. On this moss diagram the earth strap goes between bolts 38 (end cover cap) and 63 (rack clamp). Without the strap my horn wouldn't work, with it in place it does.

www.moss-europe.co.uk/shop-by-model/austin-healey/sprite/steering-suspension/steering/steering-rack-fittings-sprite-midget-948-1098cc.html



Clive Seager

Hmmm...I was totally misled by one of those awful crimp connectors. Every time I tested it, it worked. Every time I tested something else, it didn't work. Even using the correct crimping tool, I could not get it secure and had to thicken the wire with solder before it stopped sliding off. The horns work now but if they fail again I'll install the earth strap and see what that does.

Les
L B Rose

This thread was discussed between 22/11/2018 and 26/11/2018

MG Midget and Sprite Technical index

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