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MG MGB Technical - Hazard Switch Plug - '73 BGT

I think I have finally found the source of my intermittent indicator fault at last having changed switches and flasher units more than once....

The 12v feed from the hazards is not properly connected in the hazard plug, wobbling it switches the feed to the flasher switch off and on. Just what I need on a Saturday with an MOT on Tuesday.

I think the solution will be one of these?

https://www.autosparks.co.uk/hazard-warning-switch-plug

I assume it will fit just by not connecting 2 of them but I cannot speak to anyone today. That will be fun with 6 leads to make up down there!

In the interim, or ideally as a proper fix, any ideas on how I might repair the existing loose connection in the plug even if temporarily?


Mike

Mike Dixon

I think that connector will do the job, I only discovered it when installing hazards on my 73 after I had cobbled together a connector from an old RB harness.

As a temporary fix join the two green wires together - several options for doing that.

That is the fused ignition feed to the indicator flasher unit, disconnected when the hazard switch is on as otherwise you can get voltage feeding back to the ignition and fuel pump when the keys are in your hand.

But as each connection is a little socket as shown in that ad pic you may be able to put a small screwdriver down the hole and pinch them up a bit. If you have a bit of tubing the right size that can be used to push into the hole, over the socket, which pushes the tangs together then it can be pushed out the wire side.

The attached shows a bit of brake pipe being used to hold the socket while I removed the old wires and connected the new.



paulh4

Thanks Paul

'Interestingly' both the cables at the bottom of my Hazard Switch are purple, one of which connects to the flasher unit B terminal. I will do some more tracing to see what is what, what is live and move them over one at a time.

I will have a fiddle and see if I can solve the wobble effect at least for Tuesday, thanks for the tips. I have an accessories fuse box under the dash - would an alternative be to just put in a fused live feed from that to the flasher unit for a couple of days?

On the upside on further investigation it is 'only' 5 cables to rewire.
Mike Dixon

"would an alternative be to just put in a fused live feed from that to the flasher unit for a couple of days?"

Ideally fused ignition, but yes.

Didn't notice the '73 BGT' in the title until now, so yours has been added as well and could be any colour of wire, but yes it's the two that are on their own.

You may find that the green wire has been taken off the flasher unit and a wire taken from that to the switch, then back again to the flasher unit. If that has been done with a male spade to the original female then that can go back on the flasher unit for the time being.
paulh4

I have put the ignition switched fused live in and it works a treat -makes me wonder why bother going through the hazard switch?

I am struggling to see how to get the terminals out of the plug. There is no room from the socket side and its very, very tight from the the wire entry side to get in to compress the tabs -it may be a cut off and a new terminal?

Thanks for the help - all done in time for the MOT

Mike Dixon

These Durite terminal extraction tools are very useful.

https://www.12voltplanet.co.uk/terminal-extraction-tool-set.html?gad_source=1&gclid=EAIaIQobChMI6v_doZOzhAMVkphQBh0WpgCXEAQYCCABEgIbhvD_BwE

It all depends what sort of plug you have fitted. I thought the OE plugs were moulded, unlike the Autosparks one.


Dave O'Neill 2

As I say the power to the indicator flasher unit has to go through the hazard switch so that it is disconnected when the hazards are switched on.

If it didn't and the indicator switch had been left on then power from the hazard flasher to the bulbs would come backwards through the indicator switch and the indicator flasher unit onto the fused ignition supply, and from there backwards through that fuse onto the white circuit and hence to the ignition system and the fuel pump.

Some factory plugs are moulded and some not. The ones I cobbled together for my hazard switch plug came from the dip/flasher/indicator/horn switch connector on a 1980 harness, attached. Unless the hazard connector and its wires had been cut out of a 74 and later harness it would have been made up from whatever came to hand. As the wire colours seem to be wrong I assumed (I know ...) it was the latter.



paulh4

I got the extraction tool today but as far as I can see my moulded plug cannot be disassembled. I will have to to cut all 5 wires and replace it with the one I linked to above. Bit of a faff but do-able.

At least the workaround suggested will get me thought the MOT and is worth knowing as a roadside fix.

I am probably looking at replacing the loom in its entirety later this year, as long as I am careful I could run with with the direct power bypassing the hazard switch until I do? Any danger of damaging anything (fuel pump/ignition area)

Even if I forgot to cancel the indicators before I put the Hazards on I have an LED oil warning light that flashes when the engine is not running and the ignition is on. That would quickly let me know the ignition circuit was getting some power.

Mike Dixon

If it's moulded now then it was cut off something else so it would be stuck with the colours that were used in that application. It could have been supplied that way as a kit I suppose.

Running longer-term having bypassed the hazard switch should be fine now you are aware of the potential 'hazard' ...

It would be interesting to hear just what happens like that with the hazards on and the indicator stalk to one side or the other.
paulh4

Thanks - I will try it once the MOT is done having got this far and report back.

Mike Dixon

I've just seen this thread and also experienced the intermittent, and infuriating, nature of hazard switch disabling the turning signal always at the worst moments. I have purchased several switches only for the problem to reoccur. I found that wiggling the rocker in the switch frame would temporarily restore the turn indicators.

The problem I had was that the normally closed contacts that pass current to the direction flasher corrode and cause the intermittency. I solved this problem by carefully dismantling the hazard switch and solder-tinned the contacts after cleaning them with 400+ sand paper. See attached image.

>> As a word of caution, when tinning the contacts held in the plastic switch frame, you must not hold the solder iron in contact with the contact too long as the heat will melt the plastic rendering it useless. Good cleaning and degreasing of the contact with brake cleaning fluid before solder is applied will ensure that the solder flows quickly and reduce the heating.

So far all’s working fine.

Hope this helps.

Richard



Richard Thompson

Not uncommon, had that on my V8. The older rockers are easy to open up and get back together, the newer ones less so.

In my case it was hardened grease, dug that out, the contacts were clean, put fresh in and it's been fine ever since - probably more than 20 years.

Replacing switches is not a good idea unless you rally do have to, they just aren't made as well even though they might look the same. Refurbing the roadster more than 30 years ago the rocker switch logos were a bit faded so I replaced them. Probably 10 years later - and this a car that is barely used at night and not much in rain/fog, I was having to fiddle with the switch to get the lights to come on. By this time the logo on that was also fading, so I put the original switch back in and again it's been fine ever since.
paulh4

This thread was discussed between 17/02/2024 and 26/02/2024

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