How Do You Convert from 4 prong resistor to 2 prong

[jefflock]

I purchased a new underhood engine/lighting wiring harness from Year One for my 68 dart. I went and got the one for electronic ignition. Now my FBO system uses a single resistor and the new harness is set up for the old 4 prong.
On the wiring one side has 2 blue wires 1 in each hole
The other side 1 green/red striped wire and the other has a blue and brown wire in the same hole.
What do I need to get rid off to hook up the single resistor??
Thanks Jeff

 

[krazykuda]

I would download service manuals for different years with both the two wire and four wire ballast resistor and compare the wires.

 

[67Dart273]

What this amounts to:

The two terminal and "1/2" the 4 terminal works just like any old coil resistor. That is, one side is fed power from the key, the other side goes to coil

This of course is what you keep

The 4 terminal had an additional resistor fed by the key, which led off to one terminal of the ECU. This is now not used.

So all you need to do is unhook the resistor, unhook the ECU, and do some probing

First, with the above all unhooked, turn the key to "run" and find the two plugs with power. These maybe and probably are jumpered across. One of those goes to your new resistor.

Now hook your meter to coil+ and probe the remaining two resistor plugs to find out which one this is. The color should match.

The other two you can cut off the ends and tape, tuck away, etc

Do not go by the colors in the diagram below. What you are "leaving in place" electrically is the right hand half of the resistor. The bottom blue jumper over to the left bottom, and the upper left wire going to the ECU is what you are getting rid of.

View attachment diagram.jpg

 

[jefflock]

Thank You 67Dart273. I knew you would save my bacon.

 

[krazykuda]

Cut the green and red wire out.

What voltage regulator are you running?

For a 68 system, one side of the ballast resistor get s a brown and dark blue wire. The brown wire goes in to The bulkhead connector terminal N. The dark blue wire goes to the ignition coil.

The other side of the 68 ballast gets two dark blue wires. One goes to the voltage regulator and the other to the bulkhead connector in terminal N.


For the 4 pin ballast:

The dark green and red terminal goes to the ignition control box.

The other terminal below that one on the same side gets a brown wire going to the coil and the other to the neutral start and backup lamp switch.

Now the other side:

On the top terminal there is a dark blue wire that goes to the voltage regulator and the alternator.

Then a black wire connects the top to the bottom terminal.

The bottom terminal has the light blue wire with the yellow tracer and it goes to the ignition control box (orange box). This is the terminal with the blue wire to the main ignition feed.


Now this is where I get confused with the two different types of voltage regulators and their wiring. It may not be so simple as to just cut or eliminate a wire or two as the wiring is slightly different for each one and I think that you may need to hack and splice to get it right.

Is there any chance that you can send it back and exchange it for one with the two wire ballast and the electronic ignition or just the stock replacement harness and then just do the electronic conversion as in the kit?

 

[krazykuda]

I was afraid that someone would beat me to it.

Go with his advice...

 

[jefflock]

Got it all installed and working fine. Just need to tidy up everything.

 

[Rapid Robert]

What do I need to get rid off to hook up the single resistor??
Thanks Jeff

You have the 2 white plastic connectors used with the OE 4 terminal "dual" ballast/5 pin ECU setup? You want to use a "single" 2 terminal ballast with an FBO 4 pin ECU? Correct so far? Plug the "single" 2 terminal FBO ballast into the sides on each connector half that has the brown/blue on one end. Another option is to keep the OE "dual" 4 terminal ballast & jump across the brown/blue and the green/red wire terminals just like the other end is OE jumped with a blue loop. this will give a parallel circuit across the ballast & in my case it gave me 1.1 ohms (the auxiliary side had 6 ohms and the coil side had 1.6 ohms). You can also use 2 "single" 2 terminal ballasts side by side in the "dual" ballast double connector to get the ohms you want either keeping one of them unconnected for a better appearance since there is no unused terminals or parallel wiring them as the width of 2 "singles" is the same as a "dual" & will fit the 2 white "dual" connectors. You have ALOT of leeway on how much or little ballast you can get by with. Always carry spares!