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MG ZR ZS ZT Technical - Immobiliser

Has anyone added a 'hidden switch' immobiliser to their ZS180? It's been suggested this could be done in series with the inertia switch (wherever that may be, haven't got the car yet) or possibly the starter solenoid circuit. Comments?
Paul Hunt 2

Hi Paul,
Is the ZS180 in addition to the MGBs? I'd be interested to know how it compares with your V8.

The ZS180 seems pretty well immobilised as standard.
I have the hidden switch on my B, but as the ZS180 seems pretty well protected anyway, I've never bothered.

Charles Goozee

Hi Charles - yes, in addition, so by the end of the week I should have 18 cylinders of MG :o) Whilst on paper the ZS is slightly better on acceleration from the brief test drive I have had so far the V8 does seem to do it in a more dramatic fashion, a product of its more basic engineering I'm sure. But then the ZS is a more exciting and involving drive than many other modern cars, which was what impressed me so much on a test drive when they first came out.

It's a face-lift model so has the later BMW alarm and immobiliser hence good from a 'break-in and drive off' point of view, but the problem with all the factory systems is that all anyone needs to drive them away unfettered is the key! Maybe I'm just being paranoid, but I did have the V8 broken into twice whilst under my carport. The ZS is going to be even more visually exposed for a few months at least as my son's BMW Z3 M Coupe is currently under the carport, and I don't think he'd be very impressed if I used *that* as the sacrificial lamb!
Paul Hunt 2

Paul, as I am sure you know more about car electrics than I do.

However in my laymans terms the operating method of modern car electrics tends to revolve around control units that receive signals from sensors and switches and then connect power or disconnect power to devices.

I would tend to put the inertia switch in the "switches and sensors" catagory. The control unit would only expect to get a stop signal from it when the car has been moving with the engine already running. So supplying the equivilent signal at start up may not generate the reaction you want.

A more predictable result would be generated by a switch in the power supply or earth of the fuel pump. Unlike a B on SU's the ZS180 does not have 2 float chambers of fuel to use up.

Alternativly, the MEMS engine management system is conected to the imobiliser control and requires to have a positive signal from it to operate. If you can identify the relevant wire you could fit a switch to interupt it.

I hope that makes sense
David Witham

Thanks David, yes it does all make sense. It is because of the large amount of computer control on modern engines that I am wary of doing something as simple as it would be on an MGB. I was rather thinking that for safety reasons the inertia switch would be wired *directly* to the fuel pump, rather than depending on the ECU to cut it off in the event of an accident. Perusal of some diagrams is called for before doing anything, I think.
Paul Hunt 2

If you think the wiring looks complex wait until you see the diagram!
David Witham

Try asking on here -

Theres a wealth of advice for all Zeds on the forums etc.
P Murton

Good call! First item I looked at under Security detailed how water can get into an alarm unit, and how a coolant pipe rubs against the bonnet anti-tamper switch bracket, neither of which are Good Things.
Paul Hunt 2

This thread was discussed between 02/07/2007 and 14/07/2007

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