ICM harness wire

[yellow85cj]

Putting the CJ back together after way too long and doing some wiring clean up and rebuilds.

As the ICM connectors are old thought I would get some new and build my own harness.

Got out the schematics to check wire sizes. Found some things that I really don’t understand.

First, from the fuse block comes a 10 ga red wire to the ICM connector. The other side of the connector (the ICM) is an 18 ga wire. 10 ga to 18ga is a pretty big jump. Any particular reason for the 10 ga wire?

Second, from this 10 ga wire is a splice to a 20 ga wire that says “resistance 1.35” that heads off to the coil, where it splices to an 18 ga wire that connects to the coil. (it also splices to another 18 ga that connects to the starter solenoid). Is there a reason for going from a 10 ga to a 20 ga to an 18ga ? Why the "resistance" notation? Is it some special type of wire?

And again with the wire gauge change for the 4 wire harness from the ICU to the distributer/coil connector. The ICM side of the connector is 18 ga, the harness side is 16 ga. Any reason for this?

I want to move the ICM to the passenger side fender. This will involve extending the 10ga wire from the fuse block to the connector.

Do I need to run 10 ga wire? It is connecting to an 18 ga wire.

Can I use a larger gauge wire (12 ga since I have a LOT of it) for the ICM to distributor harness?

Here's the drawing that I am working from (cleaned up to just show the ignition harness)

 

[mriplaybass]

I can't give you too much information on this, especially the resistance notation. I can tell you however that it is not uncommon to start with heavy gauge wire, then reduce it to lighter gauge as it gets close to its destination. My barn has 240V lighting. The wiring that goes from the breaker box to the lights is either 8 or 10 ga, but once it gets to the light junction box, it drops to either 14 or 16 ga (been a long time since I wired it) As I understand it, the heavier the gauge of wire, the less voltage drop there is in a longer run. Therefore, when the lighter wire splits off, it is splitting from a higher voltage source than if it were run with the light gauge all the way. If you run light gauge all the way, you could damage some sensitive components due to voltage drop. As long as you can get the wire on to the connectors without damaging the connector, heaver than what the schematic shows would be acceptable.
Hopefully this answers some of your question until someone more knowledgeable chimes in. Good luck!

 

[Lumpy Grits]

Your barn lighting is 110vac and is 'split' off your 220vac. Just like 99.9% of the houses we live in.
The heavy gauge wire is to carry AMPS load, not just for voltage.

The 10 gauge used for the for the ICM is to be sure of correct voltage, when the your start'n the Jeep and the battery is take'n a hard 'pull'.

BUT-12 gauge is smaller dia(less load)wire than 10 gauge. I would not chance it. Also-You want to use stranded wire and not solid.
LG

 

[Posi]

Second, from this 10 ga wire is a splice to a 20 ga wire that says “resistance 1.35” that heads off to the coil, where it splices to an 18 ga wire that connects to the coil. (it also splices to another 18 ga that connects to the starter solenoid). Is there a reason for going from a 10 ga to a 20 ga to an 18ga ? Why the "resistance" notation? Is it some special type of wire?

Yes, it is a ballast resistor. The wire having 135 ohm resistance supplies less then 12v to the coil when running (6v if stock coil). During starting, the ballast resistor is bypassed and 12v goes to the coil. The bypass is at the I terminal at the starter solenoid. The solenoid is energized when you turn the key to start to complete the bypass.

 

[mriplaybass]

Your barn lighting is 110vac and is 'split' off your 220vac. Just like 99.9% of the houses we live in.
The heavy gauge wire is to carry AMPS load, not just for voltage.

The 10 gauge used for the for the ICM is to be sure of correct voltage, when the your start'n the Jeep and the battery is take'n a hard 'pull'.

BUT-12 gauge is smaller dia(less load)wire than 10 gauge. I would not chance it. Also-You want to use stranded wire and not solid.
LG

Not looking to hijack the thread, or start a debate, but my point was heavier gauge wire carries more juice. The breakers to my riding arena lighting are 240v. The balast is wired for 240v. After the ballast, the voltage does drop to 120v. 2 hots and a ground to the fixture =240v. The fixture is not split off of 240v. Full 240v going into the ballast. Technically, the bulbs are 120v, but the entire system is designed as 240v to provide a balanced load. All designed by an electrical engineer
Sorry for the side track.

 

[yellow85cj]

Yes, it is a ballast resistor. The wire having 135 ohm resistance supplies less then 12v to the coil when running (6v if stock coil). During starting, the ballast resistor is bypassed and 12v goes to the coil. The bypass is at the I terminal at the starter solenoid. The solenoid is energized when you turn the key to start to complete the bypass.

Hmmm, ok, so is it a special type of wire or is it just that it is 20 ga that makes it act as a ballast resistor? Does the length of it have any thing to do with the amount of resistance? Looking for the wiring for dummies version.

 

[Posi]

Hmmm, ok, so is it a special type of wire or is it just that it is 20 ga that makes it act as a ballast resistor? Does the length of it have any thing to do with the amount of resistance? Looking for the wiring for dummies version.

Part # ICR22

http://www.napaonline.com/napa/ICR22/search/?text=ICR22

 

[Lumpy Grits]

YES- it's build/made for just this purpose.
LG

 

[Posi]

See if this link works

Resistor ECH ICR22 | NAPA Auto Parts

 

[Lumpy Grits]

Mine was just a section of odd look'n wire with 2 weird look'n crimps.
Took mine out when I went to a MSD ign system.
LG

 

[Posi]

Likewise when I went gm as well
The Napa ballast resistor is black factory CJ is brown.

 

[Lumpy Grits]

Mine was wrap'd in some fabric/cloth heat-resistant tape.
LG

 

[Posi]

Maybe it was an 80's Jeep thing, my 79 was incased in silicone.
That wrap is to protect other wires in the harness from the ballist resister.
Possibly less silicone warp on the 80's wire, but that would be a guess.

 

[Lumpy Grits]

I'm think'n it was the AMC 'bean-counters' at work........
LG

 

[Woolyworm]

Search for junkyard genius jeep ignition and you will find a dizzying amount of info on these ignition systems.

I don't recommend changing any of this system without guidance (which you've already asked for). It's fairly complex for the electronically simple minded like myself. Switching to some ford parts will really perk up your ignition and help a ton with idle and responsiveness. Good luck.


Wooly

 

[yellow85cj]

Thanks for all the responses.

Still a little confused about the resistance wire, but accepting it. Apparently the coil pos side can't take more than 8 or so volts (test light dim).

Would make sense that the neg side would be the same. However in reading testing procedures, the neg side (green wire)should have more voltage (test light bright).

That is if I am comprehending the test procedure correctly.

So, making the harness between distributor and ICM should be fine with the 12 ga wire I have. It's all 12 volts.

Will need resistance wire or a coil that handles 12 volts. Apparently they are out there. Somewhere.

Also am thinking from some reading that the length of the resistance wire as well as the gauge is important. Anyone have any info on length of resistance wire?

It appears as though a Ford E coil can take 12 volts on the pos side and would not need the resistance wire. But need to do a little more research. The E coil was on of the Team Rush/Jeep Hammer things to do. Unfortunately, needing or not needing a resistance wire is not mentioned for an E coil (TFI coil).

 

[Torxhead]

I would suggest getting a full wiring schematic like what Prospero's Garage sells to see the whole wiring layout. I think you are talking about the resistance wire from the alternator. Years ago I cut mine down a bit to put out 9 volts and have had no problems with the oem coil and eventually went to the Ford E coil. You could probably set the length of the resistance wire with a voltmeter, and you can't solder it so it has to be crimped. I also use N.A.P.A.s Echlin brand icm which is a bit more expensive than most, expecting it to last which it has. If you are concerened about the heat it puts out, you could put it in its own split loom wrap. The MSD ignition is the way to go though.

 

[Lumpy Grits]

Have never regretted my MSD.
LG