Wiring 50 Ignition Switch with Custom Harness & LS

[Curt - TN]

I am installing a speedway harness in my 1950 Truck and the 3 post non-acc ignition switch has me stumped.

I checked the ignition switch with a multi-meter and it appears when the key is turned on all 3 posts make connection.

I am assuming I should be able to use the factory style switch as long as I used an external starter button, correct?

Below is a picture of my wiring diagram and here is what I think will work. Put the tan 4B on one post, the red which is battery source on another post and the pink 3B which is labeled ignition on the 3rd post. lf I am correct that should work for ignition on and off.

Next I need to care for the purple which is the wire to trigger the starter. I assume I would take power from either the ignition or acc lead and run it to a separate button on the dash then run it to the starter trigger, this should stop the start form being triggered if the key is off.

Have any of you all done this in the past and does this sound correct?

I will have the computer and fan relay draw direct from the battery but the lights, gauges and A/C would go through the ignition switch so it should not be huge amperage. The switch is new.

[mongocanfly]

Your ecm will need a switch-on power source as well..I've been wondering how ill wire mine up as well..mine has a key switch and a electric push button start..

[Curt - TN]

Originally Posted by mongocanfly

Your ecm will need a switch-on power source as well..I've been wondering how ill wire mine up as well..mine has a key switch and a electric push button start..

I am thinking we could add the power to PCM to either the IGN or ACC off the switch or the way my Speedway harness works the pink goes back and gives power to the fuse box so I could take one of my open acc lines and drive ignition power to the PCM, as I recall that is not much of a power draw.

I will post a drawing of what I end up mapping out.

[MIKESAD50]

I plan to use 60-66 ignition switch. It has acc and also a crank circuit. Using original 60-66 bezel. It looks nice and wont need to use a push button for cranking. It uses same key and tumbler as 50 set up also

[mongocanfly]

Yeah Mike...I thought about changing my switch but I wanted to keep my pushbutton start..and ive got what i think is still a set of the orignal keys...only I'm getting rid of the floor mounted dimmer switch looking button and going to a simple pushbutton on the dash close to fhe key switch....if I can..

That sounds like that would work for the ecm Curt..

[Coupeguy2001]

Try using the original switch, just wire a terminal strip to one powered leg,
For instance
key on, turns on terminal strip. push starter button, and engine starts. because;
the second hot on the terminal strip goes to a relay for the engine computer.
bring in a fused power across that relay, and the engine computer gets powered.
third terminal turns on fuel pump relay.
4TH terminal turns on things like radio relay, audio amp relay,
5TH terminal turns on air conditioning relays, etc.

Remember, the terminal strip only actuates the relay coils. you will have to have a#8 terminal either from the battery or the alternator to run all that stuff.
You can calculate the total amperage for each relay, and you might have to run a second #8 wire to another terminal post to power the rest.
Remember also, that ignition switch was made to handle about 15 amps total. over loading it could cause an onternal switch failure and it could get hot enough to catch fire or burn wires.
That's why you only run the relay coils through ignition switch. the ignition switch turns on the relays, not powers equipment.
at less than a quarter of an amp, you could run rnore than 20 relays off several terminal strips powered by the ignition switch.

So that when you turn off the ignition switch, all the relays go dead, and the battery is isolated from any electrical drain. so it doesnt go dead with the key off.