Mopar has the ceramic ballast resistor mounted on the firewall (~ 1.35 ohms) while our vehicles (and many others) have a ballast resistor WIRE (~ 1.5 ohms, ~4' 1" - 5' 2" long depending on M/Y) connecting at the ignition switch, travels in a loom under the dash, and loops back out the firewall to the coil and/or the 'I' terminal on the starter solenoid.

START bypasses the resistor circuit...gives the coil BATT voltage until started then the resistor wire circuit takes over when the key is in RUN letting the coil have < 9 VDC.

The W/r or R/w wire coming from the truck or the ICM should have the 12 VDC you mentioned. That is wired correctly for the 12 VDC to get to your HEI.

 

Thank you. That's helpful. I'm familiar with the Mopar system, and ballast for points systems in GM.

 

Interesting. The only White w/red wire I know of is the Oil Pressure sending wire. You have aftermarket gauges by any chance?
Does it share the connector with a Red w/white too by any chance? That's the water temp wire, and would confirm the identity of the White w/red.

Nope. Most Fords (and all of our trucks as far as I know) use a "resistor wire" to reduce voltage the same way that a ballast resistor with it's heat resistant ceramic base does.
The wire is between the ignition switch and the firewall. Just before the firewall and on out to the engine compartment is normal wire. Typically it's the Red w/green wire, but often the actual section that is the resistor is a sort of sickly pinkish-brownish wire. Also may be marked "do not cut - resistance wire" or something to that effect.

They accomplish the same thing as the ballast resistor by making it very small gauge with a thick heat resistant jacket, very long and looped back on itself a time or two, separate from the rest of the harness in it's own heat sleeve as well to protect the other wires around it.

Neither way seems to be more reliable than the other from what I've seen. But the heat of the resistor wire is pretty well contained, while many ceramic resistors can radiate enough heat to burn paint!

FYI, if you read about electricity, you'll often see the reference that "resistance equals heat" or "heat equals resistance" depending on what the discussion is about.

I'm sure you are in this case. But just so you know you will will still see 12v on a resistance wire if no load is placed on it to build up the heat. Even with the engine running, if you measure voltage in the first minute or so, you still see close to 12v. After a few minutes you see less and less, to anywhere between 6v to 9v at the coil end of the wire.
The best way to test is with an ohm-meter to literally test the resistance in OHMS from one end of the wire to the other.

Yep. That's the main allure I think. One wire and a pretty darn good spark. I'm a Duraspark fan from way back, but that was mainly due to GM having lots of teething problems (burned out modules) when the system was pretty new in the early seventies. Think TFI module and Ford!
Same problem, but I don't remember anyone suing GM for burned out ignition modules.

Another FYI though. To this day, if you ever replace a module, or for any reason have yours out of the distributor body, don't put it back in without it's special thermal paste/heat transfer compound under it!
It uses the aluminum body of the distributor as it's heat sink. Without the thermal paste your module can toast itself in quick order.
Just something to keep in the back of your memory in case you ever have to service one.

There was also one on top of the engine because the distributor only had a short 6" or so section of wire with the matching connector. Ford used them in several places not related to the ignition, such as over by the alternator on some vehicles (EB's in particular), so it's not actually accurate to call them Duraspark connectors in that case. But like we were saying earlier, it's what a lot of people call them because that's about the time Ford started using them on different things.

The best way to find out what they all do is to describe each wire color and we can look it up in the book. Pics do help, but wire colors are the tell.

Paul

 

Oops. Missed FB's answer while I was busy hunting-and-pecking.

Paul

 

Thanks for all the information. Yes, it does have aftermarket Temp and Oil gauges. Earlier in the post, we determined that is what my empty #2 plug is for. I plugged my tach power wire into one of the red wires since it was switched 12V.

Based on your reponses, and from poring over the wiring diagram I am starting to get a better understanding of things.

 

Cool beans. Once the diagrams start to make sense, and especially if that big Ford Light Bulb snaps on over your head, you're good to go from there!
It's a much better feeling when you look under the hood and can determine what most of the wires do at a glance.
Takes time though.

Paul

 

I’m not sure if this post is too old for me to provide an update, but I’ve got it all figured out. I met up with a guy named Jeremy who posts on a lot of the Ford truck sites. He figured that plugs A and B (as shown in the newest picture) are left over from the 6 cylinder engine that was in the truck in between the original 302 and the current 351W. Once I disconnect plugs A and B, I can then plug C into D. This will feed the empty Duraspark plug hanging from the fire wall.

He provided me with the correct engine harness that connects to the firewall plugs. Then I will have the correct wires for my oil and water sensors, and the correct harness if I ever decide to switch from the current HEI distributor to the original electronic ignition. Between all of your replies and Jeremy’s inspection it all makes sense. Thanks.

 

Nice job on getting that wiring cleaned up. Next step is to get rid of that plastic oil pressure line.

Summit has a real nice braided steel line for oil pressure...

 

Thanks Papabearyuma. I've already made the plastic line leak once by standing in there when I rebuilt the carb. Part of my goal of sorting out the electrical stuff is so I can go back to the factory gauges.

 

I'm all for keeping the factory gauges-I've certainly worked hard to get all mine working. But they're not known for their accuracy.

In many cases, you can have both. Nothing wrong with having aftermarket oil pressure and coolant temp gauges in addition to the factory. Most gauge sets also sport a voltmeter.