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MG MGB Technical - Indicator problem

Hi,
I just replaced the ignition switch in my 78B and did a bit of general tidying up since I had some custom wiring in place while the old ignition switch wasn't working.
After putting everything back together the indicators are not working. I checked and double checked all my connections and everything is good. The indicator stalk itself is relatively new, having replaced that late last year.
The hazard lights work although the switch was so hard to push I could have used a hammer. I say "was" because in removing the switch to examine it further it fell apart.
I have a feeling this is the cause of the problem and I have ordered a new switch already.
Meanwhile I want to test everything else just in case it's more than just the hazard switch but I don't want to wait for the new switch to arrive.
Can I connect the terminals on the socket for the hazard switch to simulate the switch being in place but being in the "off" position?
D O'Brien

The feed to the indicator switch goes via the hazard switch, so if that has fallen apart, you won't have any indicators.
Dave O'Neill2

provided you identify the correct 2 terminals on the hazard that switch the power to the indicator, connecting the relevant wires together will replicate the hazards being "off" which means the power to the indicators is "on". check the relevant wiring diagram for colours. But frankly I'd wait and fit the new switch as it would be the first part of an ongoing diagnosis anyway.
Michael Beswick

"connecting the relevant wires together will replicate the hazards being "off" which means the power to the indicators is "on""

This will be the two green wires that should go to the switch.
Paul Hunt

the hazard switch being so hard to push and then falling apart highlights that using and testing these switches, motors, ect. is required for reliability, of course the easiest way for most of the items is by using the car regularly

things you don't use often you want to test regularly, like the hazards, horns, heater blower, headlight flasher, dash light switch, perhaps wipers and washers, etc.
Nigel Atkins

Thanks all for the replies. I was 99% sure it was the hazard switch. Thanks to Nigel especially for some great advice. I test my smoke alarms in the house regularly but I never thought to test "emergency" devices in the car. Lucky I discovered this broken hazard switch before I needed to use it.

Following Paul's suggestion I shorted the two green wires (the bottom 2 terminals) and the indicators work! For further testing I removed the short circuit and simulated the hazard switch in the on position. That worked too.
So imagine my annoyance when I get the replacement switch today and plug it in and it doesn't work.

I have a feeling the new switch is wired slightly different to the original. The socket it connects to is definitely in original state unless I rewired it in my sleep without knowing about it.
On the socket: If you count the terminals from top left to bottom right from 1 to 8 terminals 1 and 2 are connected to the left and right lamp circuits. terminal 3 is blank. Terminal 4 is the constant power. Terminals 7 and 8 are as Paul Hunt described.
On the switch: Using a multimeter with switch "on" I get continuity between 1, 3 and 4 (terminal 2 appears to do nothing). At the same time I lose continuity between 7 and 8 which is normal.

It seems terminals 1 and 2 have been swapped with terminals 3 and 4 on this new switch. Either that or the socket is actually wrong even though I don't remember ever modifying it.
The simple solution is swapping the terminals on the socket but I've never worked out a way to remove those little terminals without destroying the socket. I am starting to wonder if the switch is for a different model.
D O'Brien

If your switch has a group of four pins and a group of two pins, with a gap between the two groups, then the hazard wires should go to the group of four and the indicator wires to the group of two.

When the switch is on all pins of the group of four should be connected together, and when it is off they should all be isolated. Because of that it shouldn't matter which of the three or four (if you can a console tell-tale for the hazards) wires are connected to which of the four pins. If some pins in that group are not connected to the others when the switch is on then the switch is faulty, or it is the wrong part.

Similarly when the switch is *off* the group of two pins should be connected together, and when it is on they should be isolated from each other. Again either green wire can go on either pin.

All pins in the group of four should be isolated from the pins in the group of two at all times.

You can use your car every day, as I did, but can still have problems when you try to use the hazards, or at the annual MOT when they check them. The grease hardens in the switches and becomes an insulator instead of a lubricant. Fortunately with these larger rocker switches it's quite easy to dismantle it (in a polyethylene bag to catch all the bits), dig out the old grease and put in fresh.
Paul Hunt

Paul,
you surprise me, if you used your car everyday why not test the hazards once a week or so to keep the switch grease more pliable and check that they are working

I very rarely use the horn when driving so will regularly test it, to keep it going and so that I have it should I ever really need it (the horn is to say 'I am here' not 'up yours' or 'get out of the way')

sure no matter what you do you can still get problems but you can cut down the odds of it happening
Nigel Atkins

Nigel

if you test your horn too often, you might wear it out and it won't work when you really need it! ;o)
Dave O'Neill2

Dave if I only got the opportunity I might but I don't so I'll never wear it out but it might disappear with complete lack of use - or be forgotten about!
Nigel Atkins

"to keep the switch grease more pliable"

When I had the problem the grease was over 20 years old. I reckon I can go more than a week without fresh grease hardening ...
Paul Hunt

Paul,
I made me post inclusive of your grease issues but the point is to operate and check the switch and rest of the system are working before you need them in an emergency and to keep the switch active

for testing perhaps you'd prefer to use a multimeter rather than the six test bulbs available :)
Nigel Atkins

This thread was discussed between 31/03/2014 and 02/04/2014

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