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MG MGB Technical - Indicator stalk switch failure?

The indicators have stopped working. I have checked that power is getting to the central contact (LGN wire) of the switch but it doesn't get out to the GR or GW contacts. I have also established that there are dead-shorts between the LGN and GR and LGN and GW contacts when the stalk is in the central position.

I have shorted across the back of the contacts from LGN to GR and LGN to GW and the indicators work.

Are failures of this stalk common? It is the Indicator/Dip/Horn version.
Graham Gilmore

While the originals lasted a long time, the replacement switches aren't as durable.
John H

Mine did, the dip/lowbeam component. One of the thin copper connections inside the switch failed. You can't get these things apart to get at it. I doubt that you could do anything anyway, molded plastic etc.
I fixed my problem by soldering a largish gauge external wire around the back of the switch, from a top rivet to bottom. Pushed into the center of the rivet and then soldered Easy fix, but it took about an hour to figure what contact did what before I could start.
You might be able to do something similiar.
You also might be able to use a modern switch of something else.

An FYI, lots of britsh cars from the 70's have the same switches etc. The Leyland Marina has lots of MGB bits in it. Morris etc
Peter

Conflicting symptoms. If power is getting to the central contact but not to the green/red or green/white contacts, then there cannot be a dead short between them, they will be open-circuit.

If you manually bridge the light-green/brown contact to *either* the green/red or green/white contacts with the ignition on do they flash then? If so then th switch is indeed faulty. You don't say the year, but the type used for a few years around 1973 had a spring wire with two arms for the central contact moved against a fixed post one side or the other i.e. exposed contacts, so you should be able to see why the contact isn't being made, if that is what the problem is.
Paul Hunt 2

I agree about the 'conflicting symptons' but I have rechecked and they are indeed dead-shorted. I have also manually bridged between the LGN and GW and GR contacts on the back of the switch and the flashers work.

The switch does have the 'spring wire' but I cannot see how that is meant to make contact with the copper studs as they do not go over far enough. I have determined that 12v is appearing on each arm of the 'spring wire' when the switch is operated.

Certainly looks like a faulty switch.
Graham Gilmore

If bridging the contacts makes the flasher work they they *cannot* be shorted, otherwise bridging the (non-existant) gap wouldn't make any difference. I suggest you are using too high an ohms scale, or if a digital instrument mis-interpreting the reading, or are measuring the switch with it still connected to the harness i.e. what you are measuring is on the harness and not the switch.

If the copper studs aren't reaching the spring wire are you sure you are pushing the switch far enough? It goes so far then needs a harder push to get it to latch. If it won't go that far maybe it is the latching mechanism that is broken and preventing it.

If the wire arms represent the centre contact i.e. light-green/brown, then it should have 12v all the time the ignition is on, not just when the switch is operated. It is the studs that get the 12v when the switch is operated, and if they do the lights should be lighting.
Paul Hunt 2

If I turn the scale down to 20K ohms then I do get an open circuit. It is still connected to the harness.

The stalk doesn't seem to move very far and the wire never gets near the copper studs so I can only assume that it is indeed bust!
Graham Gilmore

If you want a replacement switch to last a long time, give some thought to using a relay for handling the power to your signal lamp circuits and, if yours has the headlamp switching included, then also adding relays to shift the high head lamp current out of the column switch and replace it with the much lower relay energizing current. Many folks have done this over the years and they report much longer life for this switch unit, even when it has been a less well regarded aftermarket unit and not a genuine Lucas switch. FWIW
Bob Muenchausen

Not suer about the idea of relays for the indicators, not enough current drawn to worry me there. The main, dip and spots are already fully relayed and fused as it is a rally car.
Graham Gilmore

Using relays (and fuses) for *uprated* headlamps should be automatic. I've also heard of *having* to use a relay for the brake lights as the currently available items can't handle the load. But having to use them for the indicators as well as a new one on me, the current is about 2/3rds that of the original headlights, let alone uprated headlights. A few years ago I bought a new indicator/dip switch (in the UK!) for the roadster and so far it has been fine. I wouldn't give up on it yet, if you are contemplating buying a new switch then you ahve nothing to lose 'investigating' the old one as to why it isn't moving far enough, even to the point of destruction.

Looking at my old 72 switch ("If you haven't found a use for something yet you haven't kept it long enough") the wire springs only have to move about 3/16" to be on the *middle* of the copper studs, and only have to move about half that to come down off the 'ramp' and reach the edge of the stud. I think the 3-position 'click stops' i.e. in the middle and at each extremity are controlled by a ball and spring in the fixed part of the switch retained by a metal 'C' clip immediately under the arm of the switch. The ball will probably latch into one of three notches moulded into the plastic of the moving part. If it isn't doing this it could well mean that the moulding has broken or melted, which is probably terminal. But personally I hate having to buy a replacement if I can stand a chance of repairing the old (I'd applied at least three repairs to my old switch before I gave up and bought new).
Paul Hunt 2

Thanks for the input Paul but I have problems seeing how this ever worked! As I need the car for a rally in Norway soon I will bite the bullet and get hold of a replacement and then see if I can reapir this one as a spare.
Graham Gilmore

Paul,
Relays can't hurt with signals given the sometimes flimsy repro switches we are offered. Your OE Lucas switch presents no problem as is, but take a look at some of the aftermarket crap that is floating around the marketplace and you may see why I suggest it might help ~ at least a little, even if not entirely necessary.
Bob Muenchausen

Bob - relays may be necessary in some cases, and I would and have used them. But I wouldn't add them where they are not required as they *can* hurt - by adding more points of failure.

With Graham's switch something else occured to me and that is that if the stalk is moving far enough and latching into position as it should, but the spring wires aren't making contact with the studs, then maybe for some reason the wires have been bent out of position. I've checked on my old switch and it is a moments work to bend the wire closer to the stud such that it sits over the middle of the stud when operated. Be careful not to bend the wire upwards at the same time or it will lose contact tension.
Paul Hunt 2

This thread was discussed between 31/07/2007 and 09/08/2007

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