HEI converted ignition - Ignition module hot wire from harness only has 10 volts according to multi meter

[RonD]

Yes, Brown/Pink wire has 12volt ONLY when key is in START position
Red/light Green has 12volt ONLY in RUN(on)

Brown/pink wire by-passed the Ballast Resistor
Red/light Green went thru the Ballast resistor

If the Ballast resistor was not used, then the Brown/Pink and Red/light Green wires were spliced together at ignition switch, so coil and module would have 12v in START and RUN both

The wire in the engine bay would be only Red/light Green

 

[MadMax_636]

If possible. Could someone post a photo of where that looks like and where its coming from? So I know which harness I could be looking at and for tomorrow? I keep getting the urge to wanna mess around with my truck tonight but its late, dark, and humid as a swamp outside...

 

[RobbieD]

The two wires are "spliced" together at connector C102, on the cab side of the connector (the EVTM schematic shows this). Pics ain't great, but I looked and here's what I took when I did mine (back in 2009).

Red/Green and Brown/Pink going into the same connector cavity:

And here's the same two wires crimped to the same terminal after it was slipped out of the connector body:

Colors are usually hard to see on old wiring, and keep in mind, you're dealing with a truck, and wiring, that's going on 40 years old, so don't rule out that you that you may possibly have a wire or component issue that needs to be found, and addressed.

I'm not sure what you're running for an ignition system, but if you want to step up the power to it the addition of a simple relay would be one way (similar to the mod of
adding relays to improve headlight brightness).

 

[MadMax_636]

Ok, so I found the wires. Pain in the ass to find, honestly. Do I need to remove one of them from the splice? Because that's that I'm getting I have to do.

I havent done anything yet...

 

[RobbieD]

No, they need to stay connected together, so that the coil (or whatever you're running) has power in both the "run" and "start" ignition switch positions.

At this point, I'd suggest putting a voltage meter on the two wires (still joined), but with C102 disconnected (i.e.- no load). Check voltage with the key in "run" and in the "start" position, and compare the two readings. This will confirm if you do have a voltage difference in the two key positions.

 

[RonD]

You want them to be spliced together, so coil and HEI have 12v in both START and RUN

You just want 1 wire out of the splice to hook up both coil and HEI

 

[MadMax_636]

just did that. in the RUN position im getting around 12.65v and when running I'm getting 10v

 

[RobbieD]

just did that. in the RUN position im getting around 12.65v and when running I'm getting 10v

I'm stumped on that one.

Are all of the grounding cables and wiring in place and good, that are supposed to be there?

 

[RobbieD]

Pain in the ass to find, honestly.

Everything is a pain in the ass on these trucks.

That's why we love 'em.

 

[MadMax_636]

I'm stumped on that one.

Are all of the grounding cables and wiring in place and good, that are supposed to be there?

Same for me... Yeah, as far as I know. I added extra ground to the coil, dizzy, and HEI when I put all together. Maybe some of the grounds need to be redone but idk.

 

[MadMax_636]

Everything is a pain in the ass on these trucks.

That's why we love 'em.

same haha! its fun troubleshooting shit until its not haha. You leave and then just come back at it again.

 

[RobbieD]

Handy quick test. Take a single jumper cable, one end to the battery negative post, the other end to the engine block. See if the running voltage reading changes.

 

[MadMax_636]

Handy quick test. Take a single jumper cable, one end to the battery negative post, the other end to the engine block. See if the running voltage reading changes.

I tried that. Then I remembered I had run a engine ground directly to the engine block when I was dealing with voltage drop issues when I was dealing with my starter.

 

[MadMax_636]

I need to get some reels of wire as Im out. Then Im gonna get a ground block so I can ground everything to the battery. I currently cant do anything with it sadly.

Im gonna re run my grounds on my ignition just so everything is clean.

 

[RobbieD]

OK. I'm hoping that @RonD comes back and weighs in the voltage drop when running.