Lotus Elan

Anti-theft switch wiring

PostPost by: William2 » Tue Aug 26, 2014 4:48 pm

From reading various threads I have decided not to install and wire the anti-theft switch in the glove box. I am installing a new cable assembly that does have these wires included and I would be interested to know if I can leave these wires taped up and stowed or do they require connecting to each other in any way for normal horn/ignition operation. I am going to fit a battery master switch as an alternative.
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PostPost by: billwill » Wed Aug 27, 2014 12:18 am

Does it appear in any of the wiring diagrams?

I would expect it to have been wired into the wire that goes from the ignition switch to the ignition coil and it diverts the current to the horn relay?

If so you need to connect together the circuit from switch to coil and disconnect the wire to the horn relay.
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PostPost by: stugilmour » Wed Aug 27, 2014 4:47 am

The Anti Theft or Burglar switch is covered in my March '68 to March '69 Plus 2 Federal wiring diagram. This particular diagram is not done in the traditional schematic format, so can be a bit difficult to read.

Basically the switch in the run position connects the coil hot wire to keep it continuous from the ignition switch to the hot side of the coil. This is the wire pair that should be connected together at the glove box switch location. In the stock Federal Plus 2 this is shown as a Red / Green, although pretty sure during my rewire I used the more conventional White / Yellow or White / Blue included in my aftermarket loom. This coil wire may run through the sensing loop for the tach and connect to the voltage stabilizer for the fuel gauge.

The other poles of the switch are for ground (Black) and the horn relay trigger to ground (Purple / Black). Not exactly sure how it works electrically, but the idea is the coil will not see power to allow the car to start and the horn will sound if you try. Anyway, I assume these two wires can be taped off.

The Plus 2 S component connection diagram makes reference to White and White / Yellow wires for the coil (bind these two together) and a single Purple / Yellow that runs the horn compressor directly without the relay (tape this one off). I assume this version of the switch disconnects the ignition switch to coil wire and connects the horn compressor to the coil positive terminal, so any voltage at the coil primary will sound the horn.

Yours may be different than the Plus 2, but hopefully some clues. :)


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