Starter/ignition switch bypass circuit question (1 Viewer)

[trk204]

I'm planning on installing a starter kill switch using Photoman's bypass circuit detailed in this thread (and particularly post #16).

https://forum.ih8mud.com/80-series-tech/211786-starter-ignition-circuit-thought.html

I'm mostly interested in the starter kill aspect, but the bypass sounds like some decent PM aswell. The reason for the starter kill rather then a sneakier fuel pump kill (or something else), is around here we have mandatory immobilizer's on most models of vehicles. You can't get insurance if you're vehicle is on the list and you don't have one installed. Anyhow, I sure as hell don't want one installed (and don't need one....yet), but want the punk thieves to think I have one.

I plan on using an oem toyota switch (can't remember now if it's a fog or rear defrost symbol, but it's the 5 wire switch with a connector the shape in the diagram). As best I can figure from searching and playing around with the pinout, I whipped up a diagram using the switch and a relay. I'll be using a 70a relay with a 50a fuse.

I do have a couple of questions after playing with the pinouts and schematic tonight.

1. On the switch, pins 1 and 4 are for the backlight led. It seems to light up with either +12v to 1 and 4 to gnd or +12 to 4 and 1 to gnd. But I thought that led's can only be driven from one direction? .... As I was typing this out, I think I just figured it out. They're not leds and just normal lights.

2. I've seen reference in a couple posts of people carrying bypass jumper wires for the solenoid in the event or some kind of ignition circuit problems. How does this work exactly? From photoman's diagram, I understand it as you would jumper the solenoid straight a 12v source. This should engage the starter. So if the key is in the ON position while the motor is cranking, it should fire up?

 

[bhmmapping]

1) the rear heat switch uses leds, that is probably the one you are reading about.

2) you are adding a direct 12 volt to the logic side of the starter, I'm not sure you even need a 50 amp relay for that. The reasoning behind the jumper for most people is that the original wiring running through the ingnition switch and NSS degrades to the point that it will not activate the starter solenoid directly, but it will easily power a relay. I have been running like this for over a year, no problems so far.

 

[trk204]

So if I jumper the logic end to 12v, and have the key turned to the on position, will the truck turn over and fire up? Then manually break the jumper once the truck has started to disengage the starter?

 

[bhmmapping]

when I said you don't need a 50 amp relay, I meant a 30 amp would probably suffice. I used a ford starter soleoid, but it was probably overkill. In the jumpered scenario, the ignition circuit activates the relay, which in turn activates the starter solenoid. It works just like normal turning the key to start.