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Welcome to the Electric Car Weblog. In addition to links, news, and tips about electric cars and other forms of alternative transportation we are publishing an on-line diary of our current EV project. Started in August 2005 the chronicle follows the conversion of a gas powered Ford Probe into an Electric Car.

You will find articles organized by categories, along with recent comments, along the right hand column of the website. If you are just getting started with the idea of converting a gas car to electric be sure to check out Your First Electric Car

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Ignition · 28 November 05

Main wiring harness

You may remember this picture from when I first pulled out the dash. It’s the main wiring harness that snakes along the back firewall behind the dash.

It’s a little bit intimidating.

When I started cleaning up Eve’s wiring this particular rat nest was saved for the very last. I’d look at it and a little voice would taunt,

Hey, don’t fix it if it ain’t broke!

I’ve never liked that saying…

Walking by this harness I’d notice one of the connectors and think, “None of those wires do anything.” And then another connector, and another, and pretty soon I convinced myself that it would make a great Sunday afternoon project.

What you can’t really see in that picture is the huge wad-o-wires going into the fuse block in the upper left. Once the tape was removed all of the wire sprawled out like a dropped bucket of earthworms.

Before the “operation” there were thirty connectors, not counting those on the fuse block. After a Sunday of trace-the-wire I whittled it down to fifteen, with a few of the remaining connectors almost empty.

Here are four of the removed connectors:

Ignition Switch BackIgnition connectors

This is the ignition switch along with the heavy duty connectors leading to it. Big, heavy gauge wires that basically control almost everything in the car. There’s also two pair of smaller wires: one senses the key (for buzzing) and the other powers the illuminated key slot.

Ignition Schematic

This is the schematic from the manual. Imagine the red arm (Battery) being turned by the key and each position connects it to zero, one or more of the other connectors:

  • BATTERY – comes straight from an 80 amp fuse in the engine compartment, the other side of which is hooked to the battery + terminal
  • ACC – all the things you might want to run when the car is off (i.e. while parked with your girlfriend): Radio and Pwr Window
  • ON – Cooling fan, Wiper, Instruments, running lamps
  • IGN – Engine electronics, more instruments, speed control, passive restraint, etc…
  • START* – to starter solenoid via the neutral safety switch

See how ACC is on in two positions? All of the accessories are momentarily turned off while trying to start. Same goes with the ON wire. Only the IGN connection stays on during start and normal operation.

I’m guessing they did this for a few reasons: cut down on power being used while cranking over the engine, remove sensitive electronics while the heavy duty starter motor is causing the battery voltage to swing all over the place, and maybe also to remove other noises (radio, fan) so you can hear when the motor starts.

None of which really matter with an EV. It’s either on or off, no intermediate starting or getting ready stage. Although the “parking with girlfriend” ACC mode might be handy for some it can be accomplished much easier with a dedicated switch.

The other key (ahem) purpose of the ignition is demonstrated with this little animation. Move your mouse over and off the image below to see.

The dead-bolt looking thing is inserted into the steering wheel when the ignition is turned off. It’s meant to keep someone from hot-wiring your car and driving away. They now have to hot-wire it AND figure out a way to release the steering wheel.

Which reminds me of hot-wiring my Mom’s Pinto back in the 70’s and going for quick, fearful joy-rides around the block while she was away. It had a relay in the engine compartment where all you had to do was short two wires permanently and then momentarily short another wire until it started. No steering wheel lock.

My current plan is to crimp together the ACC, IGN, and ON wires, connect them to a heavy duty, normally open relay contacts with the BATTERY on the other side. Then I can come up with some kind of clever ON/OFF method: circuit, keypad, RFID, biometrics, voice, reed relay, mental telepathy.

The mind boggles!

Comments 3
  1. — James May    Nov 29, 2005 10:06 AM    #
    I used to have a yellow 1978 Austin Mini. When i lost the keys to my mini, (which I used to do regularly) I would hotwire it and drive around with the steering lock on by loosening the column outer sheath. The indicator stalks went roun withe the steering wheel. Couldn’t turn too much or you’d pull the muliplugs out and the car would stop in the road.
  2. unknown    Feb 22, 2007 12:55 PM    #

    yeah, thats all awsome!lol

  3. — Miles    May 01, 2009 22:49 PM    #

    According to my friend with the 17” biceps you can just break those locks off with enough strength. (I bet you can, kinda like the kung-fu board breaking on TV).

    I suppose you could try it out in the self-service junkyard if you are sufficiently curious.