I have a 1970 F250 w/390. This truck has a resistance wire and I'm trying to figure out the best way to install the Petronix ignitor. I'm also replacing the original coil with a Pertronix Flame Thrower coil. This coil has built in resistance so I no longer need the factory resistance wire.

I need to find a 12v switched feed. The best advice I've found in these archives so far is from RED68RANGER. He says:

"Switched 12V is on a green wire with a red stripe that runs from the switch to the voltage regulator (terminal S, I believe). It runs thru a square 4-wire connector that hangs off the inside fender well just below (and maybe a little behind) the battery. Other wires in the connector are two yellows and a BIG black one with a yellow stripe. I spliced in just above this connector to run mine."

The only problem I have with red68ranger's solution is that I don't want to run the wire across the top of the engine to the fender well. Instead, I would rather replace the factory resistance wire with a new 12v lead and follow the original wiring path.

My questions are this:

1. Does this sound feasible?
2. What color is the factory resistance wire at the switch?
3. Would I have to replace the entire length of wire from the
switch to the coil or is there a junction in between?

Actually any help would be appreciated. I don't have a wiring diagram and can't seem find much information on Ford's approach to a ballast restistor.

TIA

 

Try running the archives, and a search, there are plenty of discussions on your subject.

John

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I did search the archives. As I stated in my post, red68ranger was the best I could find. I am a new user so I suppose it's possible I'm not using the archive search correctly. But I did spend a considerable amount of time and couldn't find the answer to my questions.

 

Not familiar with the flame thrower coil but will take your word that it doesn’t need an external resistor.

Ford’s use a resistor wire instead of a ballast resistor. This wire is pink and comes right out of the connector to the ignition switch. It’s a couple of feet long and terminates at the harness connector just before it goes through the firewall to the coil along with other wires for the temp. gauge, oil pressure, etc. To bypass the resistance wire, splice a new wire onto the pink wire right at the connector on the ignition switch. Splice the other end of the jumper at the harness connector where the pink wire ends. You only need access to the ends of the pink wire as it is bundled with other wires within the harness, all under the dash. You will need to use solderless connectors or wirenuts, the resistance wire is impossible to solder to.

 

Dang, now ain't I got the big head. Personally I wasn't wild about running the wire over to the fender well either, but it can be done in a fairly good workman-like manner. I dropped it down behind the alternator and followed that harness.

DB

 

BBB - Please help me understand a few more things. I know this looks like a lot but simple yes/no answers will suffice. TIA:

1. Will jumping the resistor wire as you previously explained (in other words leaving the resistor wire in tact and splicing into it at both ends) cause the voltage to take the path of least resistance and travel through the new wire?

2. What guage wire should I use to jump the resistor wire?

3. I found the pink wire at both the firewall and the ignition switch. However they appear slightly differnt. The wire at the ignition swith has more of a purpleish hue and has the consitancy of regular automotive wiring. The wire at the firewall is definately pink and there's no questioning its uniqueness. Is the pinkish/purpleish wire at the ignition switch the correct wire?

The other wires comming of the ignition switch are orange, red w/green stripe, red w/blue stripe, black and yellow.

4. The harness connector at the firewall has four wires going into it from the switch and three wires comming out. The wires going in are white w/red stripe, red w/white stripe, pink and brown. On the other side heading towards the coil is white, red w/white stripe and red w/green stripe. The red w/green stripe connects to the + terminal on the coil. Would I be better off splicing into the pink wire at the ignition switch, bypassing the harness connector altogether and then splicing into the red w/green stripe wire that goes to the coil?

5. If you think I should stick with your original explanation, how "close" to the ignition switch and harness connector do I need to get the splice?

I apologize if my questions seen trivial. But I figure it's better to ask twice and cut once rather than the other way around. Thanks Again !!

 

Hey, no problem. If you don’t mind waiting ‘till I get home tonight, I’d like to look at the wiring diagram for a ’70. Was going by memory but you know how that goes!

Barry

 

No problem. I actually don't need the information till next week. I've got an appointment to get my kingpins replaced on Tuesday and I'm afraid to tear into this thing until afterward. It would be my luck the truck wouldn't start and I'd miss the appointment. So take your time and thanks a lot!

 

- those are good questions, and I had the same question as #1.

 

Ok I looked at the wiring diagram (couldn't wait) and under my dash for a sanity check and believe there is an easier way to bypass the resistance wire. See if this jives with your truck. On the ignition switch where the resistance wire is connected (labeled “C” for coil) there is an additional wire that goes into the same pin of the connector socket. This is a power feed to the dual brake warning light, dash idiot lights, throttle position solenoid and other accessories. You can tap into this wire for your source. Now on the other end of the harness by the firewall where the resistance wire enters the connector, there is an additional wire that goes into the same pin of the connector socket, just like on the ignition switch. This is the bypass wire that applies +12 volts from the starter solenoid when cranking. Take your new source wire and tap it into this wire, this will shunt out the resistance wire but still leave it intact. This would be the cleanest modification plus you could revert back to stock without too much fuss if needed. 18 gauge wire should be fine for this, just dress it neatly with the existing harness out of the way of the swinging windshield wiper levers.

Now the questions:

1. Yes, the current will favor the path of least resistance. A regular wire offers much less resistance than the pink wire so essentially all of the current will flow through it.

2. 18 gauge should be fine.

3. It’s hard to tell how long the wire is from the wiring diagram. On my ‘68 it goes all the way up to the ignition switch connector and assumed they all did but now I am not sure. Will check this out the next time I am in the yards. If Sparky is reading this he will know.

4. That’s a good idea, you completely avoid screwing around with the pink wire. In fact, that’s what started me thinking of another way to splice in. Using the starter wire instead will accomplish the same thing plus you are still on the same side of the harness for the mod.

5. Screw my original plan, now you don’t have to worry about the pink wire at all.

Ask away, that’s what we are here for. I don’t like hacking up a good harness but this seems fairly neat. Hopes this all makes sense.

Barry

 

Hello Barry,

Thanks for the help. What you described sounds like a good approach. However, last night I didn't even get a chance to take a look. With a 4 year old, 6 year old, and wife, I do what I can when I can. Enough rambling.

Two things:

1. I checked Motor Haven for a 1970 wiring diagram and shop manual. They didn't have either; only 1967. Do you recommend 67 literature for a 70?

2. One of the building engineers at work has a 69 Mustang and has been running a Petronix ignitor with flame thrower coil (which has built in resistance) for the last couple years. I asked him about his hookup. He didn't know anything about the resistance wire and simply connected the red wire of the ignitor to the positive terminal on the coil. He hasn't had any problems. I checked under his dash and sure enough there's a pink wire comming off the ignition switch.

Am I making a mountain out of a molehill? I would think that a resistance wire combined with the flame thrower coil which also has resistance would have a cummulative effect resulting in too much resistance. I would think the negative effect of this would raise its ugly head after the vehicle heats up and I try to restart it. (Heat builds even more resistance). It would be the classic problem where after everything cools down the truck starts right up.

I think what I'll do is try the simple hookup first and carry a jumper cable with me just in case. If I have problems then I'll tap and splice.

I really appreciate your assitance. I've become quite a bit more familiar with my truck. I'll keep you posted on the outcome. If you don't mind, I'd like to hear your comments on my questions above.

Thanks again!

Matt

 

Hey Matt I understand the family priorities, my weekend is booked up with honey-do’s.

Anyway, I called the Pertronix tech line and they said that the Ignitor ignition with the Flame-Thrower coil definitely still needs an external resistor but the Ignitor II with the Flame-Thrower coil doesn’t. That would explain why your friend’s ‘Stang is still using the pink wire. Interesting, he also said that you could leave in the resistor wire if you want with the Ignitor II, it doesn’t matter. I would try it first with the pink wire but check and see if it gets very hot. If it does then I would shunt it with the wire. Heck I’d do it anyway and see if there is a difference.

The ’67 model is unique in many ways compared to the ’68 – ’72 models. I would try to find manuals and diagrams for the correct year, have seen them pop up on eBay but you gotta keep looking. Careful though, once you start it can get addicting.

No problem, I’m always learning something new while monitoring the threads! Keep us posted on your progress.

Barry

 

I called Petronix twice myself. Talked to a different person each time. The first call was to see if they knew the color of a 1970 F250 resistance wire. You would think they would know that. But they didn't. My second phone call was about bypassing the resistance wire. The tech said that would be best, and that if I didn't, I might have problems. I wasn't overly impressed with their support on either occasion.

But I certainly am impressed with your efforts!

It's Friday 10:00 PM Pacific time. I'm half tempted to go hook it up now, but I'll probably wait till morning.

I'll keep you posted. Have a good weekend and Thanks!

Matt

 

Went out Saturday morning to install the ignitor and noticed gas under the truck. Checked the hose connection at the fuel pump and the metal sleeve that the intake hose connects to completely fell out. Not good. I hope this isn't a common problem with these pumps. Seems pretty dangerous to me.

Anyway, instead of installing the ignitor I got to replace my fuel pump instead.

Tonight the truck goes into the shop to get the kingpins replaced, some other bushings replaced, and a sway bar added.

I probably won't get to the ignitor till later this week.

I'll let you know how it goes.

Matt

 

I finally got a chance to install the ignitor. I simply connected the red wire to the + terminal of the coil and the black wire to the - terminal. Seems to work just fine. I guess I was making a mountain out of a molehill.

I'd also like to report that the new king pins, bushings and steering stabilizer (incorrectly reffered to as a sway bar in and earlier reply)really make a difference.

Thanks for the help!

Matt