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On the five speed gearbox wiring loom there is a white wire with a red tracer which exits the socket via one terminal and is immediately doubled back via another terminal. I understand this is because it is the wiring to prevent an automatic car being started in gear and as it is not needed in a manual box it doubles back effectively completing the circuit. Therefore am I right in thinking:

If this wire were cut the car would not start.
This circuit could therefore be rewired and used as one point on a two (or three) point immobilizer. (I have a tool to remove the existing pins and a number of Lucas Rist pins for rewiring as necessary)

I just wanted to check this out before I crawl on my back under the car.
supercass

I have been led to believe it is the wiring for the selector gate light. But not sure!
Easy way to find out: disconnect the gear box loom and see what happens
It is fairly easy to access under the bonnet at the back of the engine (near the distributor).

Thanks for you reply. Never thought of that. I seem to recall the wiring for the gearbox light finishing under the console but think I repurposed it. The part of the loom I have in mind is right under the car adjacent to the gearbox. Why would the cable double back though, that is what made me think it was for a neutral safety switch for an auto box. There are several wires on this loom so I'd still have to clamber under the car to test. supercass

neutral safety switch would do but inhibitor was the word I was trying to think of!!
supercass

I know which loom you are referring to, as I just renovated one
And of course the wiring diagram could shed some light here!



This loom is a pretty simple and straightforward affair

With a clockwork engine with coil battery distributer and starter next to each other starting should not be a problem to old school thieves.Steve..

The link you are looking at (white/red wire) only inhibits the starter motor. The car can be bump started even if this link is broken, so not a very good security device.

Cheers

Howard

Thanks for replies. It is only to be one point on a two or three point system, since I still have a manual fuel pump I have an electric valve which will be located in the fuel line as the second point. I'm aware that as modern cars get more difficult to steal thieves are turning to older cars. supercass

An immobilizer on a TR7?
Do you really think there are people out there that would want to steal one?
Russ

Unkind folk might say our cars already have an effective immobiliser in the form of Lucas electrics!

Axis of evil wrote:An immobilizer on a TR7?
Do you really think there are people out there that would want to steal one?
Russ

yep -mine was a few years ago!. despite the insurance chap stating it was 'not that desirable' when i commented on the low insurance!

When 2.0L wedges were current they were insurance group 7. Exotic stuff like Ferraris and Porsches were only group 8 or 9!

I still have a complete set of TR8 badges for my 7V8. I never got round to fitting them as I thought the 3.5 litre badges in 1990 would draw the wrong kind of attention. Likewise when I colour changed the car earlier, it was changed to another blue instead of the red I really wanted as it was parked on the street.

Friends of mine had a Lancia Integrale rally car and had the standard fitted imobilser fail which stranded them at the side of the stage in Belgium. Lost a good position as a result.