On another thread a question was brought up by Daveengleson on questionable wires on my fender. I started the new thread since it is another topic. I thought I knew what it was but now I think I need help.


I had what I am calling a junction block that is not wired as in the wiring diagram for the 1966 ford. Now I find that it is not a junction block.


one side of this block a black wire goes directly to the coil (shown as #16 in the wiring diagram -does not go thru the main disconnect nor the starter solenoid)
the other side of the block: a white wire comes from the starter solenoid post #3; and a second wire (red) that goes thru the firewall and is added to the other side of the fuse box (as in my second picture)


Can you electrical experts out there tell me what is going on here and what the PO was doing?

 

Looks like a resistor, to me.
Possibly for the heater.

 

KUDOS to you for starting another thread. This is a different subject - thanks!

The device is a resistor, of the type used for ignition systems. It is not Ford.

These comments tell me that the previous owner has had problems with the current to the coil and points, and added this circuit in.

Originally, the coil and points are set up for 2 voltages.
1. The first is running voltage of about 6V, not 12V, once the engine is started and the key is turned to the "RUN" position. This keeps the points from burning out too early. Ford uses a long resistor wire that is pink and green (or read and green) between the ignition switch and the coil to reduce the voltage. This wire is clearly marked as resistor, and usually has green plug ends. Other brands, such as Mopar and GM used a ceramic enclosed resistor just like the one in your picture to reduce the system voltage down to the 6V running voltage.
The 6V running circuit is the one that the previous owner apparently had trouble with, and so came up with this.

2. However, while the engine is cranking, the spark plugs need the full 12V to get strong enough spark to get the engine going. This is accomplished by having the second small wire on the starter solenoid supply the full 12V to the points/coil, but only while the solenoid is energized and the starter is cranking the engine. The second wire is normally on the small post next to the large post with the cable going down to the starter.

So, it appears a previous owner had trouble with the 6V circuit wiring, and added the resistor and its wiring in as a separate circuit.

May I strongly suggest you obtain and study wiring diagrams for your truck.
It is time consuming, but well worth the effort.

Hope this helps, and sorry to hear about the unorthodox wiring. It can be a headache to unravel and resolve.
I will be happy to help what I can, though, and I am sure others here will be just as glad to help as well.

John - Banjo -

 

My second guess, since it looks wired to the solenoid.

 

Note on the solenoid wiring:

There are 4 posts, 2 large and 2 small.

1. Large post, battery side: This receives juice from the battery, rather obviously. It is "hot" with a full 12V all the time. (Sorry if it sounds too pedantic.)
2. Small post, battery side: This post energizes the solenoid, that is, turns the solenoid "on." When the solenoid is energized, it makes the connection between the other, starter side battery post and the battery cable. This wire on the small post comes from the "Start" position on the ignition switch. When you rotate the key to "Start", you send juice through this wire to this small post and energize the solenoid.
3. Large post, starter side: This post does not have electrical current all the time. It is "hot" only when the solenoid is energized, to send current to the starter and turn the engine over.
4. Small post, starter side: This post also is "hot" only when the solenoid is energized. When hot, it sends a full 12V to the coil/points to increase the equality of the spark while cranking.

I hope this helps, even though it has no direct impact on your non-standard circuit - at least not obvious immediately.

Best of luck. By the way, if you do not have a VOM (Volt-Ohm-Meter), I would get one now. You will find it quite useful.

John - Banjo -

 

yeah, it's a ballast resistor. when i rewired my truck with the american autowire kit it calls for one of these if you have a points system. i'm not sure why. protection, i guess.

 

The lower voltage protects the points from burning out too soon. All standard, unmodified points ignition systems utilize this method of 12V at cranking and 6V while running.

John - Banjo -

 

Why didn't they just use bigger points or whatever, seems just extra parts and potential confusion, even today. Everybody did it that way, though.

 

John, That description and especially the operation of the starter solenoid is great for me. If I know how the parts work, the wiring makes sense. I do have a wiring diagram and multimeter. The truck starts and runs well currently.


But it appears to be wired wrong.


Here is what I have, and from your description, if constant power (Red) is 12V shouldn't the white solenoid wire connect to the reduced side with the (Black) coil wire. Then the coil would get 12 V on start and 6V running.


I measured the voltage and 11+Volts on the high side and 9+Volts on the low side, so the resistor is not doing much but it runs.


BTW, When I got the truck, The PO had installed a Suzuki motorcycle ignition and had cut out the harness/plug and had thrown it away. I replaced the ignition switch and "rewired" the existing mess to back to the original as best as I could determine with much help from this forum. Under the dash I connected the Resistance (Pink) wire as well as the others and it ran. Now, finding out that a separate wire (Red) is really feeding my ignition, I'm amazed that it does run. I guess more work on my back under the dash is in my future.


If I go to an electronic ignition to replace the points, does most of this go away?

 

Um, neither drawing is correct.
The "existing" schematic shows the fuse box supplying power to the ignition system, when power is supposed to come from the ignition switch.
Also, the white 12V cranking wire goes through the resistor, which defeats its purpose.

The "correct" diagram also has the power coming from the fuse box instead of the ignition switch. Otherwise, it is essentially correct.

What does the green wire do?

One thought - to return all the wiring to factory original will take a lot of time and study. It might be worth it to leave it as it is for now, until you have time to take the truck down to really work the harnesses over.
Just something to consider.

John - Banjo

 

Thanks for the help again John and all. That "green" wire is actually white at the solenoid.
As it is the coil is getting about 10v constantly so I will have to do something soon. I will go back under the dash and identify the resistance wire and see where the break is, reconnect and try to eliminate this extra circuit "red". If it still runs, then study the system for total repair.