Supply a Switched 12 volt power supply - Mopar MPI

The wiring harness umm, kinda needs a coil positive wire. What happened to yours?

On the 4.2 engine, the coil power is a ballast wire. This fat soft 5' long red or orange wire terminated near the coil and a wire is crimped on that goes to the starter relay with a second yellow wire coming from the same crimp going to the coil itself.

The starting end of this ballast wire is up near the brake master cylinder inside the harness and is a crimp connection onto the ignition module's main power which is a 10 ga. red wire with a white stripe. At this same crimp connection, a solid core thin brown wire is attached that runs to the alternator plug for the 'excite' power. This connection will have what looks like gray duct tape on it likely.

Sounds like you need to trace the alternator's excite wire to where it hooks to the ignition power and run your switched 12 volts from there.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

William Oliveri wrote:

Thanks Mike,

I have located a red wire with a white stripe that is spliced into the wiring harness which the continuation is going to the positive pole of the ignition switch.

That is like this:

Source Wire in harness >

Splice >

Two red wires with white stripes coming out of splice from source >

#1 is hanging out of the harness and was previously going to the old ignition coil. #2 is going to a relay and then the positive pole (not the battery pole itself on the switch but the one on top of the switch on the side of the battery pole) of the ignition switch.

This looks like your first paragraph discription.

Regarding the second part of your statement.

Are you saying that there should be an "Excite Wire" running from the Alternator to the ignition switch module and this is what I need to hook into the wiring harness (Mopar)?

Thanks in advance,

bill

The red/white stripe wire from the ignition should be a hot when key is in 'run' wire, right?

I have the AC Delco alternator that uses an excite wire from this source. With some aftermarket ignitions, this excite wire has to have a diode added in line or the alternator will keep the engine running when the key shuts off.

I don't know the wiring on the Mopar alternator, sorry.... I don't know if it needs an 'excite' power wire to turn it on or if it is a 'self excite' type.

Mike

William Oliveri wrote:

I just talked to Hesco who told me the one wire can be a steady 12 volt source which can come from the battery and the other wire needs to be a 12 switched source where the switched source is 12 volts in the Start and Run position when turning the key.

Any comments on this?

Thanks,

bill

Hmmm.....

Ok, maybe need to start all over again here....

I missed the part about the switched wire needing a solenoid start tag.

The solenoid start tag is the same one the coil needs on the 'coil side' of the ballast resistor 'if' your coil needs a ballast resistor! My Accel coil runs on either but my ignition module and distributor pickup need the ballast wire power to the coil.

Therefore, the red/white stripe wire wouldn't work for the switched power unless you coil runs on straight power, it would loop the ballast resistor and fry the coil. If you coil runs on straight power, then there is your perfect 'switched' wire with a starter tag right off the coil positive.

With a ballast resistor, I would instead use the wire from the oil pressure switch on the engine sensor above the starter that is used for choke and manifold heater power for my 'switched' 12 volts and starter solenoid tag that to the key switch wire.

That way if you forget and leave the key in run for any reason with the engine off, nothing will cook, no oil pressure, no power.

Mike

William Oliveri wrote:

Oil pressure switch for the power maybe...

Mike

"L.W.(ßill) Hughes III" wrote:

Crap I think my brain's going to blow up!!!

ha ha.....

Ok, I'm going to have to go home and compile all these points and see if I can figure something out.

Thanks a lot all,

bill