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MG Midget and Sprite Technical - Solution for non working horn

Now here is a good one. After rebuilding my front suspension with poly bushes the horn refused to work. As most will know the live feed goes straight to the horn and the button of the steering wheel connectes to earth via the steering column. It didn't take long to realise there was no earth at the button. Would you believe that the entitire of the front suspension and steering rack were insulated from earth. I must add I have a Front Line telescopic kit with poly bushes at each end of the shocks and it is possible that on a standard set up the leaver arms would provide an earth. The solution was to cut a section of the gasket out of the rack clamps and replace it with a piece of aluminium shim.

Cheers

Jan T
J Targosz

Jan, I had a similar problem when my horn stopped working for no apparent reason. When I finally realised that it was an earthing issue I fitted a short connecting lead to fit between the rack's casing and a mounting bolt.

I believe quite a few people have come up with a similar solution to mine but I haven't heard of anyone using shims in the way you have done. Do you have a picture you could post?


C Mee

That's interesting. I've never had a problem with this, so never given it any thought. Even when I had the fl front suspension kit on, it still worked.

So without the addition of an erth wire to the rack, or a special shim, out of the factory, where does the steering column get it's earth? I've changed my rack a couple/few times over the years, and seem to think the rack gets earthed just by being clamped to the cross member.

I'll have to look now just to satisfy my curiosity.😄
anamnesis

It's actually quite common. It happened to me when I changed all the rubber bushes etc during a rebuild. I also added the earth strap as Colin.
Rob
MG Moneypit

Where did the steering column get the earth from originally? Maybe there was there an earth lead to the rack that gets lost as it gets fiddled with.
anamnesis

In the Frogeye parts book there is no additional lead shown. It must just be the clamps holding the rack to the body. I don't have a seperate earth lead and have never needed one despite changing racks and rebuilding the front suspension more than once!
Bob Beaumont

Same with mine and used a similar solution to Colin's.
The rebuild included a new loom and there wasn't anything included on it to earth the column. The solution was simple so haven't bothered to find the cause of the problem.
Jeremy MkIII

Do the early steering columns use brass rather than nylon bushes between inner and outer columns? My MK1 doesn't have any extra earthing wire and the horn works very enthusiastically.
GuyW

Mine has felt!
Bob Beaumont

Must be impregnated with copper ease then!
GuyW

Mine has a worn nylon bush.

Had a look and definitely haven't earthed my rack with a lead either (had to look just in case I forgot lol). But horn works perfectly, always has.

Searched the archives and found this from 2010. I haven't chevked out the theory, but it sounds plausible enough, and easy to test by undoing the indicator switch. Later cars, I've also read in the archives, gain an earth when the steering lock is disengaged, but I'm not sure that seems as likely.

Paul Noeth, Indiana, USA - '66 1098

"This is just a guess, but I think the horn is grounded through the turn signal assembly. See photo. There is a wiper that rubs on the inner column. It is attached to a purple wire with black tracer that passes through the switch and into the wiring harness.

There is also a black wire (not visible in the photo) which attaches to the turn signal bracket which mounts to the outer column. The black wire also goes into the wiring harness.

So the outer housing is grounded through the switch backet, the horn switch makes the contact between the inner and outer columns, and current travels back down the inner column and out through the wiper. Or vise versa depending on the polarity of ground".




anamnesis

Doesn't apply to Frogeyes as the "turn switch" is just a left- right toggle switch at top centre of the dash.

My column has felt too, but I wondered if there was a brass bush somewhere further down inside.

The rack uses some sort of thick paper like packing pieces around the clamped part, but there is an edge or collar that could make a metal to metal contact. But dubious though!
GuyW

Had a look and definitely haven't earthed my rack with a lead either (had to look just in case I forgot lol). But horn works perfectly, always has.

Searched the archives and found this from 2010. I haven't chevked out the theory, but it sounds plausible enough, and easy to test by undoing the indicator switch. Later cars, I've also read in the archives, gain an earth when the steering lock is disengaged, but I'm not sure that seems as likely.

Paul Noeth, Indiana, USA - '66 1098

"This is just a guess, but I think the horn is grounded through the turn signal assembly. See photo. There is a wiper that rubs on the inner column. It is attached to a purple wire with black tracer that passes through the switch and into the wiring harness.

There is also a black wire (not visible in the photo) which attaches to the turn signal bracket which mounts to the outer column. The black wire also goes into the wiring harness.

So the outer housing is grounded through the switch backet, the horn switch makes the contact between the inner and outer columns, and current travels back down the inner column and out through the wiper. Or vise versa depending on the polarity of ground".




anamnesis

guy

No there is nothing inside the steering tube. It has to be just the rack that earths it on a Frog. can't comment on later cars. The rack caps are a fairly tight fit on the rack to stop any horizontal motion and that must be enough.
Bob Beaumont

Odd. My post has duplicated itself, and as Guy points out, doesn't apply to frogs anyway.
anamnesis

Surely there is metallic hence electrical continuity from top of steering column, where horn push contacts it, then right through pinion, rack, ball joints, tie rods and through to chassis possibly via shock absorbers. Arguably, the greased ball joints and kingpins will insulate but I bet they don't. Or put it this way, if you DIDN'T want it to earth you'd ensure there was an insulator somewhere.
Bill Bretherton

Bill, I think the rubber (or Polybush) inserts to the top trunion link would insulate the pathway via the top link and damper unit. My money is on the edges of the rack clamps Though it seems a bit hit or miss as an intentional design.
GuyW

Inner wishbone rubber bushes and anti roll bar drop links also insulate the stub axle. That does only leave the rack caps via the bolts into the cross member.

But I found another post in the archives from 2003 which says there was a factory fitted flying lead on their rack.

Steve Clark, 1971 midget 1275, Southampton, UK, sclarks@screaming.net
"I discovered the correct earth when dismantling my very original '71 GAN5 last year - and interestingly I've found no mention of it in any manual, the Moss catalogue - or this BB.

There's a small braided, unsheathed earthing strap that bolts between one of the O/S rack mounting bracket bolts, and the rack itself - from memory, one of the bolts that secures the pinion tail cap to the rack. I'm certain that this was an original fitment - and I took care to reinstall it when I replaced my steering."

Anybody else ever seen this? There wsn't one on an rwa Midget I had, and that was very original too.
anamnesis

Guy, I hadn't thought of the trunnion rubber! Must be the rack clamps route then. Mine certainly earths.
Bill Bretherton

I was going to fit a wire between the rack clamp and one of the screws securing the pinion cap. When I removed the clamp I found a fibre shim around the rack which was obviously acting as an insulator. I simply cut a small section away and replaced it with a few layers of aluminium foil. Everything works fine now. Without seeing it for myself I would been certain the front suspension would have earthed out somewhere.


Jan T
J Targosz

Bill,

The tie rod ends will have plastic liners so an insulator.
David Billington

This thread was discussed between 10/07/2021 and 12/07/2021

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.