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MG Midget and Sprite Technical - 70's puch button immobilizer?

Hi all again this evening,

After a successful day with the engine being freed up (previous thread direction of rotation) I now have a question based on my old time recollections.

I am a 70's lad and I remember from that time cars with a rubber covered push button usually hidden under the dash that was either an immobilizer or some sort of starting restriction thingy. Never had one myself on any of my cars however there is one on my midget. I don't really want to be messing with any wiring or anything if I can help it at this point in time cos I havn't yet had the engine running.

Can anyone fill me in on how it worked / how you work it or what it stops / interfers with? Or is this an irrelevant bit of kit that won't stop the car starting? (It is like a rubber covered button that you can press in the middle of and is placed where the driver has easy access to it. Its not the 4 way flashers or anything like that). My brother in law who gave me the car is not able to give me any advice as he can't remember what to do for anything like this now.

Any recollections as well as known facts that may help?

Thanks in advance,

D Squire

Its not factory

Is there brown wires hooked up to it....if the correct brown wires are connected that would kill the entire car...just like if the battery was not there

If its well hidden and works... Id leave and use it esp for short trips into wont stop a top end pro but it will slow them down and those that use youtube to learn to hotwire...would certianly draw attention to them selfs and burn lot of time...making it an abondon theft

Prop and the Blackhole Midget

A photo might help.
Dave O'Neill2

With standard distributor based cars you can simply switch the white/black (-ve side of the coil) to ground. (effectively gives the same symptoms as if the points were always closed - i.e. engine turns but will never fire). Many places you can hide a switch to do that that only you will be able to find before the battery gives up.

Edit : ahh - didnt realise you had something already. Not sure if the above helps at all.
Dean Smith ('73 RWA)

Hi Guys,

Thanks for comments and ideas.

Pic of button and position shown in pic.


D Squire

And the requested car pic (after much moving of stuff).

D Squire

If the only wires going into that switch/unit are the two red ones, then all it's likely to be, is a straight forward make and break push switch.

If you want to remove it, then either:

1)Just join the two red wires together.
2)If this kills the ignition, then keep the two wires seperated, as it''s likely that in joining them, you're probably earthing both sides of the coil.

But it's and odd place for an immobiliser switch. Anybody getting in would see it and try it. Not much anti theft value in that.

Can you follow the read wires and describe where they connect? Best with a picture if possible.
Lawrence Slater

if there's a non-standard steering wheel on the car it could be the horn button?
David Smith

Lawrence - I have a kill swtich on the fuel pump of my B (all the cars actually but the B is relevant here). It is in full view - in the centre of an additional console with 4 other switches. There is also a hidden one for back-up.

One time when I took the car for it's test and had left it there for the day for when they could fit it in, i got a phone call to "come & pick the @#$% thing up, it won't start!!!!" Turned out they'd been fiddling with the console witches checking lights etc, and then turned them all off. Including the fuel pump. And 3 mechanics for half an hour were completely baffled.

What hope a passing yobbo then?

The tricky thing about a fuel pump switch is that it goes for a little while (COOL, it must be OK eh?) then mysteriously stops. And some owners have found that even when you know there's a fuel pump switch it is sometimes a complete mystery as to why the car has died!
Paul Walbran

Hey paul

You just hit on something ive been kicking around for a long while

Anti car jacking set up... Ive been thinking of adding several more feet of fuel hose and hooking up a hidden switch to a relay so that the switch has to be pressed while starting the car with the key.

So in the event of a car jacking all you have to do is turn the car off.. let the thug have the car, telling him the car is almost out of gas and the gauge dost work... He restarts the car and leaves you save the car travels about a mile and dies from lack of gas... You walk to the car and start it up.. travel a ways down the road find the guy thug... Run his ass over, get out and beat the sh*t out of him with a baseball bat... piss on his face And take his cash for the waste of time he caused you and leave him crying for his mommy in a ditch

Removing his man hood with a rusty dull pocket knief is optional but encouraged to stop any future breeding of low life trash

Prop and the Blackhole Midget

Thanks guys, lots to go at. I will try tracing wires to see where they go, I know its not a factory original fit by the way the wires run. Will put battery on car tonight or tomorrow morning and go through options.

D Squire

Hi Giys,

After much scabbling about it looks like the horn.

The investigation has told me to be skeptical about the condition of the wiring as the horn should be on the indicator stalk.

When this car was first garaged I suppose the MOT was more lax.

Just another thing to add to the list.

Thanks for input, probably in touch again shortly.

Thanks again,
D Squire

David Smith

I thought you where referring to one of these '70ies Puch...

Alex G Matla

Hi Everyone,

I have reopened this cos the engine now turns, the starter works and turns the engine over (definite yippee this time). Plugs back in and there is fuel poured directly in float chambers. Tops on float chambers.

No spark at end of HT leads, no spark coming out of coil.

Immobilizer? can't find anything, the previous button I found was the horn, works just fine with battery on.

Your thoughts / courses of action would be much appreciated. Everything is as it was before I found the engine would not turn, old, the lights work etc. and the starter turns all the time it is asked, battery keeps going, (thats newish), the alternator is not being driven so I can get to plug 1, my thoughts are to check the voltage in to the coil, (need to get a tester or in line bulb for this evening), however your thoughts are still much appreciated.

Back to work for now!

Thanks in advance,

Dave (the not quite going yet Midget)
Dave Squire

This thread was discussed between 27/05/2012 and 06/06/2012

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