Using alt light as relay trigger?

[79SIg]

I'm currently trying to wire up a relay so that the start on the key/switch I'm rigging up will disable the key/button after the car has started so that if anyone borrows the car the flywheel is saved from having the starter eating the teeth.

Would I be safe in assuming that I can have my ground of the trigger for the relay going to the alt warning lamp on the alternator side and have the +12v side to Ign? I'm basing this on the fact that both sides of the bulb have +12v present after the vehicle is started and would disengage the relay.

Just wondering if anyone else has done this before or would be able to confirm that its ok to do this.

[geezer101]

It sounds like a complicated way to disable the ignition. Check here for for some tips and ideas on how to make it hard for the bad guys to make off with your pride and joy - http://www.sigma-galant.com/viewtopic.p ... ing#p64210 (try to ignore the posts recommending booby trapping your car... )

[A112H]

Am I correct in thinking your reasoning behind this is to prevent flywheel damage when starting?
Does this actually happen enough to warrant taking these steps?

[79SIg]

Well, I have friends that have the "I wonder what happens if..." question pop up all the time. I'm thinking more about the road worthy when I drop it off for that.

And I already know about earthing the coil ect, actually thinking of getting a spare coil and throwing it under the drivers seat, possibly one in the passengers seat too.... 45kv up the arse will definitely tell you to get out..... Will be on a nice little deterrent for them.

And using the light does work. Tested it today using 12v only, just moved the trigger off the alt to the batter wire, hey presto it turned off!

[A112H]

I think you are confusing the spelling of "friends" with "douche bags"

[shuggy]

you could wire up a normally open relay to the starter that is closed by the the current of the oil pressure switch? or the alt warning light, however if one of these switches is turned off while your starting your car your started will die.. Only way i can see it working is if you have a 'one use only' relay that once you have turned the key to start and back to on, it will only work again if you turn the key to off and then back on..

[79SIg]

I am going off the alt warning light. By all rights the alt light should always be on during cranking due to the massive voltage drop and current draw of the starter. I'll see how I go after I fit the new engine and box next week.