Electrical Switched 12V source for HEI

[notch351w]

Looking for a switched 12V source while in Run and Cranking for an HEI setup on my 1985. Should be 12-14 gauge.

Tried the Red/LightGreen off the ignition switch but that only powers in Run. Attached the wiring diagrams and don't see any right off the switch that provide power in Run and Start. Have a temporary setup as a physical toggle switch running right off the solenoid to the HEI but would like to integrate into the existing harness. Thanks.

 

[Noobz347]

That's not how you do it.

Whatever switched source you want to use is fine but you don't use that to draw power. You use it to trigger a relay that draws power directly from the battery.

 

[cbac89]

Wow. I just posted this same thing. I am looking for a trigger for my relays that has constant power in Run and Start.

 

[AeroCoupe]

Here you go. You will need to find where the R/LG (Red / Light Green) and BR/PK (Brown / Pink) wires are tapped and a R/GR wire is spliced to the taps. This wire is hot in run and crank. See below and realize I pulled this from my wiring diagrams and EVT for my 1993 but I think this wiring holds true for the 87-93 cars. I know @Mustang5L5 has the EVT for a 1988 car so maybe he can check his to confirm.

Find the wire and probe it and that should get you what you need.

 

[cbac89]

Here you go. You will need to find where the R/LG (Red / Light Green) and BR/PK (Brown / Pink) wires are tapped and a R/GR wire is spliced to the taps. This wire is hot in run and crank. See below and realize I pulled this from my wiring diagrams and EVT for my 1993 but I think this wiring holds true for the 87-93 cars. I know @Mustang5L5 has the EVT for a 1988 car so maybe he can check his to confirm.

Find the wire and probe it and that should get you what you need.

I tried that Red/light green and it doesnt provide power in run.

 

[AeroCoupe]

How far past the splices did you check? It’s where I tapped for the MSD on my Thunderbird.

 

[limp]

On my 83, the red/light green is a resistor wire that goes to the coil... It is powered only in the run position of the key..
Spliced into it at a connector, is the Brown/Pink wire which has power in the start position of the key...
Thought this might help.....

 

[cbac89]

I tried it in the 3 locations shown on the diagram. Do i need to tap in after the R-LG and BR-PK splice before the DB B?

 

[cbac89]

On my 83, the red/light green is a resistor wire that goes to the coil... It is powered only in the run position of the key..
Spliced into it at a connector, is the Brown/Pink wire which has power in the start position of the key...
Thought this might help.....

So do i need to splice in where ive added the blue X on the attached diagram?

 

[AeroCoupe]

I believe so.

 

[limp]

I bypassed my red/light green with a new wire as it was getting very hot.. I think due to it being a resistor wire..
Newer coil in my car, so I did not need the resistor wire for the old style oil filled coil anymore, and I did not like the hot wire in my loom, although I believe this is normal for a resistance wire in the ignition...
I then had problems with the car not starting when cranking it in start mode, but when I let off to run mode the car would fire up....
Checked my wiring diagram and I could see ( missed it a bunch of times) that the brown/ pink wire was spliced into the red/light green wire at a connector.. This did not make sense to me as two " hot" wires were being spliced together.....
Testing with my good ole test light, going from run to start with the ignition switch shuts off the current from the red/light green and turns on the current to the brown/pink, then shuts off the current to the brown/pink and turns it back on to the red/light green when the key switch goes back to run... I believe this is to give the coil a full twelve volts for starting in my era of car
Again, my car is Duraspark/Carburetor, but the ignition switch is the same in your car I believe......

 

[limp]

So do i need to splice in where ive added the blue X on the attached diagram?

I think so, but I do not know... Doesn't make sense in your car as full 12 volts would be OK for the run cycle... At least I think so.....
Wonder if Ford did this so they did not have to change the ignition switch or the connector that plugs into the ignition switch?.... But if yours is like mine your are not getting any current when you turn your key to start without having that brown/pink wire spliced in.....

You can test your switch like I did with a test light......

 

[notch351w]

Starting to make sense now. Noticed the brown/pink was hot in Start with red/green hot in Run. And they're next to each other on the ignition switch. Had them cut under the dash and was going to splice them together both to 1 wire to the HEI. Did this temporary toggle switch instead for the time being.

On the attached PDF says they're spliced to the same splice number. Not sure where tho physically it is in the loomed up harness.

 

[cbac89]

Yea, thats my plan. I dont know where they spliced those two wires together, but if i get 12 v from the brown/pink in start, im going to just splice it to the red/l green and then run a wire to my relays. Hope that works.

 

[limp]

On the attached PDF says they're spliced to the same splice number. Not sure where tho physically it is in the loomed up harness.

My wiring diagram says they are spliced together at C-218.. Says its behind the fuse panel... Its a 4 prong connector
Again this is for an 83 with Duraspark...