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MG MG Y Type - Trafficator/slipring earthing.

A bit of electrical help please.
My trafficator wiring is I believe WSM correct. New loom, so it's down to me if not. Slipring fingers all rebuilt by a machinist mate, and the external contact screws all test ok for continuity.
Both trafficators test perfectly when power is put to the ring terminals when they are OFF the slipring - ie direct feed from battery negative to the trafficator via the ring terminal. BUT when I put the ring terminals onto the slipring screws, and test the trafficators up at the steering wheel terminals (timer assembly not fitted, so just power to trafficator ring terminals direct from battery again), two things happen: (1) the nearside trafficator works with vigour, but the offside trafficator does not - just sparks on contact with the ring terminal. (2) the steering column below the slipring becomes "live", only when power is put to offside wire.
Does this sound like the finger in the slipring assembly for the offside trafficator is making contact with the steering column where I presume it should not?
I can have the column with slipring assembly back out and on the bench in half an hour (lots of practise!), but would appreciate some thoughts from others who have been here.
John.
J P Hall

Hi John,
Have you installed the earth wire at the base of the steering shaft. The inner shaft runs in two felt bearings and is insulated from the rack by the 6 doughnut rubbers at the coupling.

You need to bridge the rubbers as in the image above, or it will find an earth through something else. The earth is shown on the wiring diagram in the WSM, just not where it is fitted.

Also double check your terminals under the horn push - many people get that wrong too - don't assume it was installed correctly when you found it.

I ALWAYS use star washers when I am making an earth connection - with a dab of heavy grease to delay the rust that will eventually give you a bad earth.

99% of Lucas electrical issues are caused by bad earthing. Do you have a good earth flow from Body to Chassis - Engine to chassis - all with star washers both ends ?

Safety Fast

Tony
The Classic Workshop
Black Mountain QLD


A L SLATTERY

I have to agree with Tony about ensuring correct earthing of the steering column. As designed I have to say that it was poor though and suspect that many cars do not have a good earth here. The fixing which Tony shows the earth strap being attached to is unreliable in itself as to operate correctly it needs to make good contact with the column and who wants to scrape the paint away to enable this. The other end is also problematic as just trapping it under the bolt, as designed, is bound to give an insecure earth return as the rubber cones still insulate it. I suspect a variable contact is the best we can hope for here which comes and goes as the column turns. Either that or the normal return is actually through the various cable sheaths like the choke and starter.
On the point of John's original problem I would need to ask if when he says that he is testing it with the timer removed I assume he means the whole timer unit. Simply shorting either of the indicator tails should operate the associated wiper. If not the problem must be the sliprings. The easiest way to check them is by looking for continuity to the slipring connections with all other wiring disconnected. I suspect he will find one side is OK whereas the other is not. When I was going through this I found some old writeup which showed the distance from the inner column to the slipring unit. This is adjustable depending on the underdash fixing of the outer column. I believe the diagram is on this site somewhere but I find the search function here a hurdle too far.

Good Luck
Ian

BTW what does WSM mean?

good luck
Ian
ian thomson

I have just reread your post John and it us clear that your problem is not so much an open circuit to the sliprings so much as a short to earth on one of the wires or slipring fingers. The sparking and the column becoming live proves this. It strikes me the problem could be with the inter-column wiring as there is not much room in there, especially in the spring at the top. Your ohmmeter should find it though.
Ian
ian thomson

Tony, Ian - you're not going to believe this.
Took out the steering column again this morning; undid everything I'd put on the inner slipring where it's exposed (there used to be a rubber boot, but I've never seen one - thick-walled heatshrink is great); was about to split the two halves of inner slipring connector, when a little voice told me to check the wiring where it exits at the bottom of the s/column and travels upwards, protected by the u-shaped tube. Sure enough, there glistened a little dot of solder, where I'd joined the wires and applied heatshrink - but obviously not well enough! The heatshrink protection had somehow rubbed and exposed the wire to the metal sleeve - which as we all know is connected by sprung clips to the lower portuon of the steering column. Hence the live steering column when I energised the driver's side trafficator!
SO - two hours all up, everything back in and tested. Now both trafficators leap to attention and, better still, return home. Anyone who's spent hours sorting these idiosyncratic bar-stewards knows what I mean.
By the way Tony, I prefer the earth wire to be under the nut, so that it contacts the metal of the flange. Either approach probably works fine. Thank you gentlemen for your words of wisdom. Onward and upward.
John.





J P Hall

John,
My earth connection is how it was done in the factory and I have never needed to change it. However, I did add a star washer under the tube clamp just to get through the paint there.

Put the wire under the nut and you will eventually break the earth connection as it get tangled as the shaft turns - seen it many times.

Ian - the inner shaft of the steering is insulated from the entire car - there is no possible way for earth return via choke or starter cable.

Safety Fast

Tony
The Classic Workshop
A L SLATTERY

In my own defence, I took the precaution of keeping the earth strap as short as possible, and after multiple revolutions I'm pretty confident it can't snag on anything. But I have been warned. In case anyone is confused, the loop of cable visible on the upper side, photo 2, is the wires going up the column, which will be pulled tighter when I make the steering wheel connections ( for the umpteenth time) tomorrow.
I'm happy to have sorted out the mystery short which gave me the live steering column yesterday!
John.
J P Hall

Tony I have contemplated this earthing strap on many occasions and concluded that even if connected as the factory intended I cannot understand how it works. I take your point about the inner column being separate from earth, or at least without the earth strap it should be. The only reason I can see for the strap is to provide an earth return for the horn contacts anyway. As such it has no affect on the indicators at all as some suggested when answering John's query. As far as I can see to provide a proper earth bond the strap has not only to go under the nut but under the robber cone as well to fully contact the metalwork of the steering rack (which would also need the paint scraping off). I do wonder if a rogue earth return is to be found on many cars as owners use the underdash mounting for the outer column as an earth for extra wiring they have fitted but even this would not explain how it worked from the factory, and besides the owner would also have had to provide an extra earth bond here (as I have) and any effect this has on earthing of the inner column would depend on some sort of rubbing contact between the inner and outer columns. As I say I am puzzled and accept I must be missing something but really can't see what it is and I hate that. Congratulations for having bottomed it though John though this raises another question about your earth strap. Has it got continuity and does the horn work as surely a fuse should have blown?

Ian
ian thomson

This thread was discussed between 14/01/2023 and 15/01/2023

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