[jhein]

Originally Posted by Formulas

follow that wire back to the bulkhead obtain either male or female packard 56 terminal run a length of new 12G wire to dist cap
its pretty simple really

Sounds easy enough. Any idea what the yellow wire is for?

[West Coast GTO]

It would take a while for the wire to heat up to get hot enough to deteriorate even if the wire was too small. That would carry the load until it deteriorated enough to stop making contact, be conductive. If the wire was WAY undersized, it would have failed immediately( an open circuit).

Originally Posted by jhein

All very good points. Here's one aspect I'm struggling to understand. Why was it working fine for quite a while and once it started acting up it progressed really fast? The harness is from American Autowire and was brand new. If it had small gauge wires that would overheat, why wouldn't it have happened from the start? OTOH, if it was due to inadequate gauge wiring, then the wires would overheat but the total amperage carried would still not be excessive and blow a fuse, is that thinking correct?

[tjs72lemans]

For mine. I disconnected the points resistant wire at dizzy and tucked it into the harness in case I ever wanted to go back. Plus no one sees it. I ran a separate wire from ignition terminal on fuse block out to HEI. Works as it should.

[Formulas]

yellow wire? i have no idea where it breaks out of the harness or what its next to or anything

the best thing you can do to be independant and know all things electrical is get a factory wire diagram for your car, they are not expensive and will show you wire size color end to end logical routing with all factory splices

[Kenth]

Originally Posted by jhein

OK so they did use the resistance wire in the AAW harness for power to the distributor. Picture below. I don't know what the yellow wire is for but it appears to be part of the AAW harness.

So where's the best place to tap into the ignition source?

The yellow wire is IGN #2 (full voltage at START position)
The resistor wire is IGN #1 (reduced voltage for points at RUN position).

You have a couple of options.
1. Use a regular 30 amp relay to the HEI and have your current AAW wires control it (#85 on the relay).
2. Disconnect and isolate the resistor wire, find the IGN terminal on fusebox and have a wire out to the yellow wire, put them together to + on HEI.

HTH

[jhein]

Originally Posted by Kenth

The yellow wire is IGN #2 (full voltage at START position)
The resistor wire is IGN #1 (reduced voltage for points at RUN position).

You have a couple of options.
1. Use a regular 30 amp relay to the HEI and have your current AAW wires control it (#85 on the relay).
2. Disconnect and isolate the resistor wire, find the IGN terminal on fusebox and have a wire out to the yellow wire, put them together to + on HEI.

HTH

Thanks Kenth.

I think I'll just run a new wire.

The other question is should I trust this harness now? As far as I can tell, none of the insulation on the other wires melted, just the tape.. But I can't really see everything. Do I need to worry about that or just as long as everything works it's good?

[25stevem]

You will be fine as long as the other wires near by the one that started to melt are not showing signs of getting crispy.

[SRR]

HEI's use a lot of power hence the giant wire on factory set-ups. I once converted an old truck I had to HEI and had mistakenly wired it to a circuit breaker...truck would stall out on my wife and not restart until I came to the rescue. Oops...I've run engines on my test stand without the alternator hooked up and the HEI would kill the battery enough to stall the engine after a while.

[jhein]

Originally Posted by 78w72

strange, they never mentioned changing the dash harness when i bought mine... & im not sure why that would be needed as there is no connection from the 12v ign/coil wire to the internal dash wiring. the tach wire is completely separate from the dash or engine bay harness.

hope you get it figured out & back up & running.

I talked to AAW today. He stood by the need to change the dash harness if you use their HEI engine harness. I don't have the circuit diagrams so I don't know. But he's saying that it goes through the dash harness somehow. So I guess, according to the guy I talked to, that if you mixed an HEI modded engine harness with a factory dash harness you would not have 12 g wire all the way from the ignition switch to the distributor.

[jhein]

Well, if I was disgusted before, I'm not sure what comes after that but that's what I am now. So I go out to wire the distributor directly to the ignition circuit on my fuse box. Then I find that the terminal is missing. I don't know if it broke off or if that is a seperate part that plugs in there. I gently tugged on the other terminals and it doesn't seem like they come off. So either I can find a way to connect to that terminal or then what? Will i have to find the terminal coming off the back of the fuse box?

[66sprint6]

I've used these in the past and they worked great. Scroll down.

https://www.wirthco.com/battery-doct...ccupied-blocks

[jhein]

Originally Posted by 66sprint6

I've used these in the past and they worked great. Scroll down.

https://www.wirthco.com/battery-doct...ccupied-blocks

Awesome. Thanks. Even found them on Amazon.

[dataway]

Looks like that fuse box could use some cleanup ... some quality time with a dremel wire wheel ... but a total pain with it installed. Might help to pull all the fuses and clean up the ends.

If you are handy with a soldering gun you can make your own fuse taps with some brass shim stock and spade terminals.

[jhein]

Originally Posted by dataway

Looks like that fuse box could use some cleanup ... but a total pain with it installed.

That's the thing. Installed is the PTA.

I am fairly handy with soldering. Figuring out how to set it up would be the hardest part for me.

[Kenth]

Originally Posted by jhein

Well, if I was disgusted before, I'm not sure what comes after that but that's what I am now. So I go out to wire the distributor directly to the ignition circuit on my fuse box. Then I find that the terminal is missing. I don't know if it broke off or if that is a seperate part that plugs in there. I gently tugged on the other terminals and it doesn't seem like they come off. So either I can find a way to connect to that terminal or then what? Will i have to find the terminal coming off the back of the fuse box?

You can use the ACC terminal for your HEI as well.

[dataway]

Originally Posted by jhein

That's the thing. Installed is the PTA.

I am fairly handy with soldering. Figuring out how to set it up would be the hardest part for me.

You can remove it from the firewall and make access a bit easier, but anyway you look at it .. it's a lot of time on your back or knees. However .. from the rust on some of the fuse holders and fuses .. probably going to bite you down the road.

Cut a 1/4" wide strip of brass, maybe an inch long, solder a male spade on one end, plug the male end to the female end (already attached to wire), wrap the brass around the appropriate end of the fuse. Although you'd probably have to buy the shim stock (could even use copper if you want) around .010" thick would do.

I did my fuse box when the whole harness was out, much easier on the bench ... replaced a bunch of the fuse holders too.

Kenth ... do you happen to know of a power source in the fuse box that provides power with the key on, but does NOT turn off during starting .... but does turn off when the key is off?

[78w72]

Originally Posted by jhein

I talked to AAW today. He stood by the need to change the dash harness if you use their HEI engine harness. I don't have the circuit diagrams so I don't know. But he's saying that it goes through the dash harness somehow. So I guess, according to the guy I talked to, that if you mixed an HEI modded engine harness with a factory dash harness you would not have 12 g wire all the way from the ignition switch to the distributor.

i dont doubt they said that, but they didnt mention it when i bought mine, i specifically told them i was reusing my fuse box that was in good condition, maybe 72 is different than 70? regardless so far im going on 6+ years with no issues, plenty of long street drives & lots of drag strip time. but i will definitely check the fuse block/ign wire for signs of heat.

what i was saying is that the actual dash harness, what feeds the gauges & inside lights & accessories etc, is not related to the ign power wire. there may be a short run of wire from the fuse block to the actual bulkhead but the "dash harness" is not related to the ign on these cars... did you change your dash harness too?

[242177P]

Originally Posted by jhein

All very good points. Here's one aspect I'm struggling to understand. Why was it working fine for quite a while and once it started acting up it progressed really fast? The harness is from American Autowire and was brand new. If it had small gauge wires that would overheat, why wouldn't it have happened from the start? OTOH, if it was due to inadequate gauge wiring, then the wires would overheat but the total amperage carried would still not be excessive and blow a fuse, is that thinking correct?

Resistance generates heat, and the heat generated creates even more resistance. Just keeps getting worse and worse. Classic death spiral.

[Schurkey]

Originally Posted by 242177P

Resistance generates heat, and the heat generated creates even more resistance. Just keeps getting worse and worse. Classic death spiral.

"Thermal runaway".

[Kenth]

Originally Posted by dataway

Kenth ... do you happen to know of a power source in the fuse box that provides power with the key on, but does NOT turn off during starting .... but does turn off when the key is off?

The two lower to the right on jhein´s fuse box should be feeded with a pink wire and work like you asked.

IIRC, 1975 and later uses a pink wire from the ign switch to the HEI. No longer need for thefullpoweratstart yellow wire from R terminal on starter (F-body) or from ign switch (A, B or G-bodies) that whas needed for the points ign.