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MG MGB Technical - Ignition cut out switch

If I wanted to immobilise the ignition with a hidden switch. Where would be the best place to put it & on which wire?
Iwan Jones

In the past, I have switched the positive side of the coil to ground. You can put the switch anywhere you'd like. Worked fine for me. Some cars I left the switch in the engine bay, some I ran the wire under the dash somewhere. Just depends on how convenient you want it to be... to you and to the potential thief.
Roger Hotelling

Roger,

Did you mean to say the "positive" side of the coil? If so, then you must have a positive ground car. If you ground the positive side on a negative ground car, and then turn the key on, you will get smoke! You will have a direct path from the battery to ground, and there is NO FUSE in that circuit to protect you!

The kill switch needs to be on the distributor side of the coil. When the points close, they connect that side of the coil to ground - the kill switch acts as if the points never open.
DANMAS@aol.com

in the past i have installed a switch on the feed side of the coil. however becuse of the high loads through this feeed i would suggest that you install a switch which can ahndle this. do not attempt to use a "normal" dash switch. hide the thing to suit yourself..under the seat..behind the dash...just as long as it is out of sight.
ian holliday

It seems to me that a cutout switch in the fuel pump circuit may be more effective to thwart a their. When they go to steel a car, don't they often 'hotwire' the ingition circuit? If the hidden switch worked the fuel pump, it might frustrate 'em a bit more, to where they'd be more liable to give up.

Joe
Joe Ullman

My spelling's gone to hell. Must be the mixed nuts!
Joe Ullman

Joe

If you had a switch on the fuel pump supply it would not stop the car from being drive a short way….then it would have o be left in a possible dangerous position….or it may even be driven on to a truck to be carried away!!
ian holliday

Ian,
Point well taken. Maybe a double-throw, single-throw switch to cut out both circuits. That ought to give 'em pause.

Joe
Joe Ullman

Ian. Are you saying to put a heavy duty switch on the battery side of the
coil? If so just make sure you never accidently have it on when you turn on
the ignition switch as DANMAS mentioned. If you do you may wish it had
been stolen when you attempt to repair the damage it can cause. Same
thing if someone tries to hotwire it. FWIW, Clifton
Clifton Gordon

I read somewhere that the overdrive switch (the one on the wiper control) is a favored place for a cut out switch (of course only if you don't have an overdrive) - the switch was included in many North American cars that were not equipped with an overdrive.

rn
RN Lipow

Ian, if the car could be driven onto a truck, it could surely be pushed onto a truck, even if you had a kill switch on the ignition. Not saying an ignition kill switch would be bad. I've tried to drive away with my fuel pump switch off, several times, and have barely made it out of my driveway, but it depends on how much fuel is left in the bowl. The plus of the fuel pump switch is the switch does not cut power from the battery, so radio presets and clocks on new stereo's stay in tact. You can also cut the switch easily in case of an engine fire, preventing the fuel pump from feeding the flames (could just turn the ignition off, but this isn't always obvious in a panic situation). I have also found it very handy to be able to turn the ignition on without the fuel pump pumping for certain repairs and problem diagnostics.
Bottom line is that both are a good idea.
But I have a question, are MGB's really a hot car theft target. Honda civics seem to be big out west. Cars are usually stolen either for parts, or transportation for another crime, it seems an old flashy MGB wouldn't be too well suited to either.
Just a thought
Bill
Bill Mertz

Connect a wire from the brakelight switch to a switch under the dash panel and then on to a car horn under the instrument panel (or the bonnet). Worked for my sisters' MG Metro. They got the car going but the horn blared at every junction in the road. They left the car after about 100yards.
rob

That's hilarious! I love that idea.
Joe Ullman

Not strictly concealed, but I fitted a standard battery cut-off switch (between earth and battery -ve terminal) into the removable cover over the battery hole, so that I could reach it between the seats when I get in. It's really to stop the battery running flat, rather than as an anti-theft device, but with the big red key out you wouldn't spot the hole to put it in (black carpet helps I guess) unless you knew it was there.
Andy

I used 2 cut off switch?s. The one under the dash (I cut into a white ignition wire) is a rocker type switch which shuts off both the coil and the pump (check your wiring diagram). I also use the other connectors on the rocker switch to run that to a pulsating light which I mounted in the console under the radio, looks like the car has a anti theft device. I also cut into the harness in the trunk and put a rocker switch there which shuts off the fuel pump. That?s about as much as I can do, if they really want it, they will get.
Bruce

I once heard of someone using a 1/8 inch mono earphone jack and plug, instead of a switch. The jack was wired into the circuit in place of the switch. The plug was then simply wired to connect the two "sides" together. When the plug is inserted into the jack, it completes the circuit and allows the car to start.

The advantage of this is that you can carry the plug on your keychain and take it with you when you leave the car. It also might not be quite as obvious as a switch to a thief looking under the dash.

Such a plug/jack is available at any Radio Shack.
Paul Noble

This thread was discussed between 12/01/2002 and 14/01/2002

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