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MG Midget and Sprite Technical - Steering Column Earthing

My Mk IV Sprite's horn used to work perfectly well but now it refuses to play.

The car has a Mountney wheel and the slip-ring to horn-push lead inside the steering column shaft came with some sort of insulated device like the 'pencil' that some Spridgets use. After the horn started sounding on its own accord I investigated to find just a load of plastic crumbs instead of an insulator. I jury rigged it with insulating tape, which served well for several years. I suspect the deterioration in this tape caused some sort of short circuit which killed the original horn. I recently re-built this arrangement with a biro tube and more insulating tape - a specially bought 'pencil' didn't do the job as the Sprite has the older type slip ring and wiper.

I've just been fitting new horns, which work fine when the earthed to anywhere on the body except for the inner steering column shaft!

The question is: How/where is the steering shaft earthed?

Running a connection between the horn lead and earth anywhere on the chassis sounds the horn, but not if it's earthed to the steering wheel or shaft.

My multimeter (I'm no expert with it) shows 12V. On the Ohm meter setting it goes off the scale on all sensitivities when measuring anywhere except between the steering shaft and the body when I get a reading of 500 ohms (if I've read it correctly). Could something have broken/ gone missing / deteriorated?

If all else fails, I'll just have to rig a separate button on the dash when MOT time comes!

Any advice or suggestions would be appreciated.

Colin



Colin Mee

Steering wheel with horn-push contact (and very rusty nut!)


Colin Mee

Hi Colin,
sounds to me like it's your pencil connection, try a test wire from your horn push to slip ring to confirm this.

Purple wire from the fuse (box) goes to the horn(s) and purple/black wire to horn push, so the switch on on the earth side - all connections have to be good.

As a non-electrician I find a long length of twin test wires with the ability to fit various connections extremely helpful in testing, the test meters only help so far.

Should you need it this John Twist vid for how to get the steering wheel off but you will need a glamorous assistant.

http://www.youtube.com/watch?v=lwf2BDC5DMo
Nigel Atkins

Thanks Nigel.

I've been using the long bit of wire to test all the permutations I can think of!

Wheel-centre contact to body (steering column bracket)- horn works fine.

Wheel-centre contact to earth on the direction indicator switch (just peeping out behind the indicator arm in first picture)- horn works fine.

Wheel-centre contact to steering column shaft or steering wheel boss - nothing - though the multimeter picks up 12v and a high resistance.

Incidentally, clamping a jump lead between the steering shaft and the main engine earth braid, everything works on the button! That's why I think it's a shaft earthing issue.
Colin Mee

Should be an earth braid from the rack mounting on driver's side to the rack itself (pinion bearing cover). That's for the early rack, not sure what the arrangement is for the Triumph rack.
Bill
W Dunsmore

Thanks Bill.

Mine's a 1967 Sprite so an early rack I think, definitely not Triumph!

I don't recall ever seeing anything braid-like there, and I haven't had the rack off. However, I just tried the jump lead from the pinion bearing cover to earth and it it all worked as it should.

I can't see anything on the MGOC site but I'll keep looking - or improvise.

Many Thanks

Colin
Colin Mee

Some used an earth strap between the column and the O/S engine mounting.
GuyW

This is the earth braid that was on the car when we got it, looked like it had been there from new.
Bill


W Dunsmore

Bill. Thanks for the photo, that's exactly what I needed. Not to track one down, or make one.

Thanks Guy. That's one avenue I had thought of, but there doesn't seem to be any electrical continuity between the steering shaft and the outer column/sleeve. I'm not keen on attaching anything to the shaft but could possibly arrange a wiper/slip ring arrangement connecting to the engine mount.

Thanks.

Colin
Colin Mee

I had this when I refreshed the engine bay on our Frog. The horn worked ok before the refresh but not after. In the end I had to put an earth lead between chassis and steering rack, just as Bills image shows.
Not sure why but I suspect it was the kindness I showed all the components with lashings of chassis black paint and/or the slightly thicker than original rack seating on the rack mounts.

Rob
MG Moneypit

Colin,
by wheel centre contact do you mean your pencil?

I remember you're swapping from one to two horns so you you checked you've wired them both the same?

The horns need very good solid and clean connections to get them working properly, if your horn worked with just the one former and you didn't have that earth strap you could try only connecting one new horn and see if that works.

I'd use the meter to see if there's electric getting through from car battery or meter battery in continuity but that won't mean it'll be enough to get the horn(s) working.

If the horn worked before it must have earthed through somewhere even if not the usual place or properly.

When I changed my horns the previous mismatched horns did work (or at least one of them can't remember for sure) but when I put the new replacements in it took a couple of connection cleaning sessions to get them both working properly every time. When only the high tone horn worked my wife would laugh as it sounded a bit weak and apologetic compared to the twin tone.
Nigel Atkins

On the MK111 midget there is a sort of cardboard gasket which wraps round the rack inside the mountings. This would prevent the rack itself from earthing to the body - hence the braid. These gaskets don't seem to be listed for the frog.
Bill
W Dunsmore

Nigel.

I assumed it was a pencil that I needed, so I bought one but when I came to fit it, it just doesn't go. I've tugged pretty hard on the wire that is there but it won't come out and I don't want to break w wire inside the steering column.

I would love to see a drawing or cross-section of the top end of the steering column to see how it should be, but, for the time being I'll continue with my biro tube and insulation tape arrangement.

The old horn is definitely dead and my two shiny new Lucas snails sing out loud and clear whenever I manage to complete the circuit.

______________________________________________________

STOP PRESS - Cracked it!

Having looked again at Bill's photo, I went and took another look. There is definitely no trace of a braid ever having been there, however, a bit more googling brought me to mg-cars.net and a forum featuring a Mr. Nigel Atkins and Guy Weller, along with the pic below posted by J. E. Davies who says that this lead is often forgotten (omitted) during restorations!

Running a small lead crocodile clipped onto the two screws shown gave me fully functioning twin tone horns operated by the horn-push.

Now I just have to make up a suitable permanent connection and I'll be road-legal again.

Thanks to all for the help, pics and advice.

All I'm left with is the question of why was it working previously and why did it stop working? Perhaps I'll stumble across the answer when I'm working on a different problem!.


Colin


Colin Mee

Well done.

Sorry I thought you'd tested that with a clip lead, hard though it is to believe my reading and writing is worse than usual at the moment because of new glass (and the headache they're giving me).

>>If the horn worked before it must have earthed through somewhere even if not the usual place or properly.<< - with the power of the horns I'd want to eliminate any stray earths for them though.
Nigel Atkins

Nigel

I thought I'd tried all the permutations with the long lead, but thanks to the gloom down there, plus my line of sight, I hadn't spotted the 1/4" screw heads until I saw the photos. All I could see was the big hex nut on top of the rack and I didn't fancy anchoring a connector with that!

I agree that the horn MUST have earthed somewhere, I just can't work out where. As there was a voltage but a high resistance I assume that the earth had found an unorthodox route. I also think the crumbling pencil arrangement might have lead to a a permanent short circuit but, thanks to the resistance, the horn wasn't getting enough current to make it sound but enough to kill it and drain the battery in the process.

I wasn't considering a short circuit as a reason for the battery failing to hold a charge for any length of time, I assumed it was age as it was already a few years old when I got the car in 2012. I guess that speaks well of the durability of Numax batteries!
Colin Mee

Colin

Have a look at item 28 here, although it is not currently available

http://www.moss-europe.co.uk/shop-by-model/mg/midget/electrical/switches-controls/fascia-column-switches-1275-1500cc.html
Dave O'Neill 2

Colin,
as JT says batteries are one of the most over sold items on a car, look after them and they'll look after you - and there's not many electrical extras on standard Spridgets.

Seeing photos from clean fresh cars like Bill's helps no end, my car's mainly black stuff on black stuff and black muck and mud and dust, everything blends into one.

If you feel your rusty nut spoils your concus car I can put a shiny new one in the post to you for a share of any future show winnings - I think I've measured it right at three-quarter inch thread, one and five sixteenths inches across the flats and about 8mm deep (five sixteenths of an inch if you must) but I'm not good at seeing things close. It doesn't fit my mongrel steering rod.

You should really have a safety washer beneath the nut but I've never found the nut on mine ever to be the slightest bit loose when I've had to remove it.
Nigel Atkins

Wow, what a place to hide that in the parts list, well done Dave.

I can't remember having item 28 when I fitted a reproduction twin sprung spoke steering wheel to my Spridget but in my mind it had the later pencil because I'm sure I had to look for the later slip ring - but my memory isn't the best.

Colin,
shiny nut shown in this photo (and later slip ring to left).


Nigel Atkins

Dave

Thanks for spotting that. It explains a lot - the arrangment is pretty much as I expected but my mind was stuck on feeding wires in from the wheel end. From the look of it I should be able to extract the wire from the slip ring end and re-build the assembly. Does anyone need a 'pencil' as mine is clearly spare!

I had actually briefly visited that page on the MOSS site, but I was looking for earthing braids and completely missed the slip ring.

Nigel - I can assure you that my Sprite is far from concours and the rusty nut is not in the least surprising. Do you think the rust might help it drip the wheel better?

I have never had the wheel off and have no plans to do so at the present. If/when I do I'll consider a washer but at the moment the nut is flush with the end of the shaft thread and a washer might reduce the contact area (reference the recent thread about stud lengths and minilites).
Colin Mee

Colin,
as I always say about my car - not even the rust is original.

I don't think I've got a washer under the nut on mine either, I can't remember for sure, but I do know the nut that's fitted is slimmer and flush with the end of the threads hence the shine new nut going begging.

>>Do you think the rust might help it drip the wheel better?<< er, you what?
Nigel Atkins

>>Do you think the rust might help it drip the wheel better?<< er, you what?

oops - typo!

grip!

Not good from someone who spends his day proof-reading other peoples' work!
Colin Mee

Nigel it wasn't always clean and fresh. If you look carefully through the grill aperture you can see the earth braid through the muck. Only taken the bare fourteen years to get to the rebuild phase, hopefully back on the road this year.
Bill


W Dunsmore

Something odd about your near side indicator
GuyW

Thanks for the photo Bill. I've promised my Sprite a full rebuild in a few years but I'm enjoying driving it too much to take it off the road at the moment. Perhaps a project to keep me busy when retirement hits!

In the mean time, I have installed an earthing lead between the pinion cover and the rack mounting bracket. Lo and behold a lovely twin-tone Paarp when the horn-push is pushed. Good job SWMBO and daughter were at the dog show or there would have been complaints about the music from the garage! If we could upload sound as well as pics you'd be able to hear for yourself.

Still can't work out why it was working at all before I installed the new lead unless it was earthing via the felt bushes!

Thanks for all the advice and pics.

C
Colin Mee

Ha Ha, nearside indicator came in a box of bits with the car, unfortunately a wing for that side did not accompany it. The wing I subsequently acquired does have the indicator hole in the correct position for the year (1972) although that was just luck as I didn't know the difference at the time. Amazing what you learn on this forum.
Bill
W Dunsmore

Bill,
you're too fussy your car don't look bad in that last photo (other than missing bits).

Colin,
I meant to put, I had a GT6 that earthed the horn in the same (similar?) way and sometimes when the car was lifted the horn would parp intermittently.
Nigel Atkins

Re-activating in response to S. Johnson's thread as the link I posted doesn't want to work.

Colin
C Mee

Whenever I am in a scrap yard, I try to grab some radio grounding straps from there. Sometimes they are under the bonnet to firewall and under the dash from radio to chassis.

Proper woven straps with good eyelets on the end. If I need a bigger hole, I just drill or ream it out.

Have a supply around here somewhere but they are adaptable to all things electrical and look factory too.

Clare
Clare Ravenwood

Clair

This is a dumb question ...but i dont know the answer

Im assuming radio wire is similar to the ground wire that goes from the trans to the chassis and is kind of a mesh

What is the purpose of radio ground wire over just a length of regular insulated good heavy gage cooper stranded wire to connect / complete a link of the ground ciruit

I see that radio wire as you call it in various lengths and thickiness at tractor supply store hanging on the wall next to the battries ... but rarely any place else

Thanks

Prop
1 Paper

Yes, Prop, the straps are a kind of braided mesh affair. The straps you see at TSC are battery ground straps and a piece of wire would suffice for the radio. The braided straps just look better. Just a case of esthetics I suppose. Most of the straps are from Chrysler made vehicles..

Clare
Clare Ravenwood

Thanks clair

Seems like alot for simple looking good while driving....haha

I had to add an extra ground to my dissy because of my block being powder coated... so i was never certian if i really needed the braided ground mess strap instead of my make shift ground everyday wire which seems to work fine

So thank you

Easy as she sails

Prop
1 Paper

This thread was discussed between 08/03/2017 and 04/09/2017

MG Midget and Sprite Technical index

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