1968 Red wire on the solenoid (remains hot)

I am hoping to get some help with one of the few remaining items to be able to get my car on the road again, after a 4-year extensive restoration.
We buttoned up everything and noticed the red wire (655) coming from the solenoid stays hot even with the ignition off. We disconnected the wire from the solenoid, and it remains hot.

In tracing the diagram, the yellow & black wire (654, 37, 152) from the solenoid also gets spliced and goes to alternator, then routed to the voltage regulator and ends up connected to the Ammeter. The red wire (655) goes to the yellow under dash plug and gets connected to the Ammeter.

We did the following tests.
1. Disconnected the yellow plug under the dash that comes in from the firewall harness to the Ammeter. The power to the red wire is off (with red wire to the solenoid disconnected)
2. We switched the yellow & black wire (654) for the Red (655) on the solenoid (with only red connected), then the yellow and black also stay hot (with the yellow under dash plug connected).
3. With the yellow connector disconnected yellow wire is still hot, red is not. Where is the power coming from?
4. With both Red + Yellow & Black wires connected, both wires remain hot.

I am very concerned about two hot wires causing issues or even a fire hazard. Is it normal to have both the yellow/black (654) and red (655) wires remain hot?

Do we have a faulty Ammeter? Or faulty wiring or a short? Would there be any issues with leaving the yellow plug under the dash disconnected and the red wire at the solenoid disconnected & taped off?

Any help would be greatly appreciated. Thanks in advance.

First, a small correction. The plug with the two wires you're looking at are wires 152 (yellow) and 38A (black). Wire 654 (yellow) actually connects to what eventually becomes 38A in the main engine harness at about the middle of the front crossmember under the radiator. Now to the question. Wires 655 (red) and 654/38A (black at the solenoid) form a circuit through the ammeter. The ammeter theoretically measures the direction and amount of the current flow. Both sides are "hot" all the time, as both sides are connected to the battery and unswitched. You can plug your yellow under dash plug (connection to ammeter) in and connect both wires at the solenoid and it will be fine.

With that said, if you want to get down in the weeds, the Ford ammeter is a parallel circuit with a large gauge piece of copper wire. The idea is to measure the voltage drop across that piece of wire and which side is higher. The higher the current flow through a given resistance, the higher the voltage drop. Unfortunately, Ford didn't spend the money to build an ammeter precise enough to read the amount of difference between the two connection points, which are maybe 4 feet apart. Under most conditions, the ammeter usually just vibrates around the center mark, if it moves at all. The best bet if you really want to keep track of your charging system is to get a Rocketman voltmeter conversion. Somewhere in the archives is a tutorial I did on installing one.

Steve

Thanks Steve. Appreciate the reply and the clarification on the wiring and info on the voltmeter conversion.

Are you saying both wires remain hot because they are both connected to the solenoid? The issue that we have is that even with the red wire (655) disconnected from the solenoid, the red wire still remains hot. So, we are puzzled as to where the power is coming to the red even with that wire disconnected from the solenoid. Thank you.

The red wire is supposed to be always hot.

Mosesatm said:

The red wire is supposed to be always hot.

Click to expand...

Thanks Arlie. Sorry, don't mean to be a pest. So, with the red wire disconnected at the solenoid, is the voltage passing through from the yellow wire to the red wire through the Ammeter?

Basically, that's correct.

Steve

Thanks Steve. Very helpful. We did see slight movements on the Ammeter when starting up the car so it must be working. Thanks.

You're welcome.