1965 442 - Ordering a new Engine Harness. Car is stock except for MSD Distributer (ready to run type, no 6AL Box). The new harness will have a wire/resistor wire combo that connects to the coil, but this is not needed for the MSD Coil/DIstributer. Do I just leave this disconnected ? The MSD just requires a 12 V feed.





Schematic

MSD

 

You can remove the wire from the bulkhead connector, solder a new 12ga wire to the pin and run it to the coil+ terminal. The other option is to run a 12ga wire from the IGN spade terminal in the fuse box to your coil+ terminal to provide a keyed 12v.

 

Does the resistor wire continue into the fuse panel (interior) side of the circuit, or is it just in the engine compartment?

 

Just the engine compartment. It does not go inside the car.
I did what Eric suggested, removed the resistor wire from the bulkhead connector. I went to my (then) friendly Chevy dealer where I knew several of the employees where they fixed me up with a few new wire ends to fit the bulkhead connector so I didn't need to cut the resistor wire. Neat & easy. I ran the new wire beside my existing wire harness and used a new reproduction wrap for the wire harness to hide all the wiring modifications I did, like an electric choke for my Quadrajet, gauge wiring, etc.

 

Where would the "IGN" terminal on this fuse box be?




Fuse Box

 

What is the label where the 2 red wires are connected? Where do they go?

 

There wasn't one in 1965.

- Eric

 

Those are both taps on the ACC circuit.

- Eric

 

They are accessories, don't recall exactly what, I'll have to check when I get home. I do know the resistor wire and the yellow/black wire next to it (that goes to the starter solenoid) were capped with my previous engine which also had an msd distributor. It all worked fine. What does the yellow/black wire do that is connected between the coil and starter? Didn't seem to be needed.

 

Not being familiar with the 65 fuse box but those taps serve the same function I'm assuming as the IGN circuit. Change of plan would be to tap into the black/pink wire at the ignition switch or idiot lights junction and run that wire to coil+.

 

The yellow/black is the resistance bypass wire. With your previous engine using an MSD, I'm assuming your resistance wire is already bypassed to the coil.

 

So long as you want your car to run in the ACC position...



I'm ASSuming you meant previous, but I think I actually like it better this way...

- Eric

 

Two Questions.

1) I presume the terminal that the resistive wire is connected to is 12V, and this wire drops the voltage for the points. So if you connected a regular wire to this terminal it can be connected to the msd coil.

2) what is the purpose of the bypass wire? Is that also a 12v wire? Can that be used for the 12v coil?

 

True. The pink wire on the other side of the firewall connector is a regular copper wire.



Have you looked at the wiring diagram in your Chassis Service Manual?

The Yellow/Black ballast resistor bypass wire connects the starter solenoid R terminal to the (+) terminal of the coil.

When you place the ignition key in the START position, you energize the purple wire, which energizes the solenoid coil, which pulls in the solenoid, kicking the starter gear into mesh with the flywheel, closing the high current connection between the battery and the starter, and also closing the connection between the battery and the Yellow/Black wire, and thus feeding +12V to the coil (+) terminal.

This provides a higher voltage to the coil while cranking, ensuring that the car will start in cold weather, or when the battery is low.

Note that somewhere in the 1965 range, the function of the ignition switch was changed:
Earlier ignition switches energize the Pink IGN wire OR the Purple START wire, while
Later ignition switches energize the Pink IGN wire AND the Purple START wire.

If you have the earlier version, then your car will not run without the Yellow/Black bypass wire.

- Eric

 

Damn spell check...

 

Then you don't think right.





- Eric

 

So I'm thinking I have a later version since the bypass wire and resistor wire were both capped.

Bottom line - I can order the stock harness, leave the resistor disconnected, add my 12v wire for the msd, and connecting the bypass wire is optional, correct?

 

That pretty much proves it.


Correct, though the bypass wire is never a bad idea.

- Eric

 

Then what possibly would those 2 red wires be connected to in ACC only?

 

Thanks for all the replies, very much appreciated. I ordered the new harness, and actually they modify it for use with the msd. The resistor wire and bypass is replaced with a 12v normal wire for the coil (+). Perfecto!

 

Originally? Power windows and power antenna.

Now? Who knows?

- Eric

 

Aftermarket gauges

 

So its a keyed in the run position source, not an ACCY sw. position source. Basically the same as the IGN terminal on the later models.

 

Where did you get that information?

I posted the actual schematic from the '65 CSM. The two taps on the bottom are clearly on the ACC circuit and not the IGN circuit.

As I said, those terminals are fine if you don't mind your car running in the ACC position.

- Eric

 

Lets back up, the op stated his aftermarket gauges are hooked there and you stated the they would be used for p/windows or p/antenna. If the those terminals were only powered in the accy key position then having those items wired there would be a bit inconvenient.

 

No, you're not looking at the big picture.

The ACC circuit is powered when the switch is in the ACC and IGN positions.
It is off in START.

The IGN circuit is powered when the key is in the IGN and START positions
(though, as I mentioned, some earlier cars are different).
It is off in ACC.

The Indicator Lamps circuit is only powered when the key is in the IGN position, and is grounded when the key is in the START position.

The START circuit is only powered when the key is in START.

- Eric

 

Ok, for some reason my brain was not working earlier and I had to look at an earlier full wiring diagram to get reacquainted with the earlier fuse boxes.