Howdy folks, me again.

So today I decided to pull out my DSII wiring harness, give it a look over, and clean it off. The reason being, the PO decided there was a wire in my harness that he wanted cut out/off. The truck ran fine, so I wrapped it up until I got time to take a look at it and see what it was doing and whether or not I needed to put it back in place like it's supposed to be. Obviously the factory didn't send out any vehicles with cut wires.

So, I pulled out my wiring harness (which was the first time anything had ever been disconnected regarding the ignition components. I'm still running the original ignition module and distributor! Quite a feat for an ignition system that's known to have modules burn out due to heat exposure) and gave it a good cleaning.

What I discovered was that the wiring harness for my DSII ignition actually has TWO red wires in it! Obviously I'm perplexed. It was my understanding that it was supposed to have only one SOLID RED wire going straight to the coil, and the temperature and oil pressure sending unit wires for the gauges in the instrument cluster are red with a white stripe and white with a red stripe.

I can't find the answer as to what this wire does. It isn't a solid red wire, it's red with what looks like faint yellow hash marks with red in the middle. Kind of like this:



My mystery wire is the "What is this?" wire:



The closest answer I got was that it might be used to power chokes, but my choke wire originally came off the alternator.

Now, here's the kicker, my coil is getting 11.6 volts in RUN with the engine off. Not 7.5 like I've heard it's supposed to be.

So what's the deal? Did this plug into emissions equipment? Is the coil getting reduced voltage in RUN only with the engine actually running and not off as well? The PO cut off the original connector, so I assumed the connector looked like what went on the oil pressure and water temperature sending units.

Thoughts?

 

The red/yellow-hash wire is used to power various solenoids around the carburetor area, its source is usually from a black box mounted inside the cab on the firewall near the gas pedal:





You might check your voltage at the coil with the engine actually running, not just with the key in RUN.

What year is this thing?

 

That's what I was thinking as well, crank it and get it running then see what the voltage is. I have a feeling once it's put under load, the voltage will drop down like it's supposed to be. None of the wires under the dash have been hacked up or tampered with that I've seen, so I know the resistor wire and the ballast resistor are still in place. It cranks and starts with no issue as well, so that tells me it's getting voltage in START and RUN.

I haven't seen that black box before under my dash, but I'll give it a look tomorrow and see what I find.

It's a 1983 F150, 49-state emissions, no A/C, power steering, power brakes, 300-6/4.9L with a standard transmission.

Is it possible that this wire actually went to the little throttle kicker solenoid? I had a solenoid that used to sit on the side of my carburetor. I never could find the plug for it. The thing you see plugged in was the electric assist choke element.

 

The IGN module might not be stock. An original Motor Craft module will conduct current with the key ON, engine not running..... but some of the after market IGN modules might not and thus the higher (same as the Battery) voltage. You have to have current flow to see the voltage drop across the resistor wire.

Just check the coil positive at idle to see if it is lower.
JIm

 

That's what I planned on doing. I'll do that tomorrow, as it's pretty dark outside now.

I've got 11.6 volts with the key in RUN, engine off (which could be due to the voltage drop from the wiring and switch that the electricity has to go through. The longer the wire and the farther the electricity has to go, the greater the voltage drops due to resistance of the actual wire itself, if I remember right). Battery voltage is at 12.26 with the key in RUN, engine off. So I'll see what it is tomorrow at idle on the positive side of the coil and see what it's getting.

 

Yep.

Well, I think so....



Was looking for one of his posts that has a Ford wiring diagram showing that black box, too, but couldn't find it easily....

 

That sounds right to me, Chris.

I'll check voltage at the coil here in a bit.

 

D7AZ-12250-A .. Resistor Wire-Ignition Coil (Motorcraft DY-213).

49" long / Color coded RED with GREEN stripes / 1.30-1.40 ohms resistance / #16 gauge wire.

1980/89 F100/350, Bronco & Econoline.

 

Thank you ND. They're definitely not green stripes, they're yellow hash marks, so it's not the resistor wire.

Am I correct that the resistor wire is underneath the dash above the ignition switch and not in the DSII harness?

Tested the voltage at the coil with the motor running, and got ~9.8 volts. So it's not the optimum ~7.5 voltage, but the resistor wire is working somewhat. I also cleaned the terminals on the coil and the little wires that hook to it with fine grit sand paper.

No black box up by the gas pedal either. Just firewall.

 

Any that I've seen are in the harness from the ignition switch to someplace near the firewall. I forget the color(s) (pink?) but it's pretty obvious it's not a normal, stranded wire like the others, it's got a real thick, spongey coating and is labeled. I think it might be a solid wire, don't remember for certain and it'd be a big hassle to dog it out of its storage box in the garage....

 

Looks like the mystery is solved then.

Thanks everybody!

 

Actually, I think the "What Is This?" stray wire in your diagram was used to power the fully automatic electric choke on certain V8 models that had the Motorcraft (Holley) 4160 4V option. This wire provided a full 12 volts to power the choke.

All other models used a thermostatic "hot air" choke and an electric assist that had a wire that connected from the choke cap to the back of the alternator. The connection here only provided about 9 volts. The red wire was simply taped up out of the way and left unused if your truck didn't have the 4V carburetor.

I got my own Duraspark II wire harness from a 1983 model truck and it also has this same unused red wire.