Electrical question on 64 Falcon instruments

[Voldad]

I finally hooked the battery up and I am closer to bringing the thunder on my 64 Falcon barn find, after 30 years in a shed.

When I turn the key to the on position the only life in the cabin (besides me of course) is the old after market radio mounted under the dash. 

It is wired directly to the fuse box and is grounded somewhere under the carpet. Nothing else lights up or moves. I am guessing that every instrument is grounded separately so not sure where where to start troubleshooting. Any guidance is much appreciated.

Bill

[Bloo]

Got a wiring diagram? Can you post it?

 

Old Fords of this vintage have an "accessory" feed off the ignition switch and an "ignition" feed. It is not entirely logical what feeds what. Sounds like one might not be working. The gas and temp gauges probably(?) don't ground. The little rectangular box that feeds them power probably does though. An oil light would ground through the instrument cluster or dash. So would the dash lights. Without looking at the car, all of this probably grounds where the instrument cluster bolts to the dash. The GEN light would not be grounded.

 

Fords like this have a stater relay near the battery somewhere they refer to as a "starter solenoid". A short positive battery cable goes to a large post. On that same large post should be a smaller wire with a large ring terminal. This feeds power to all the little stuff in the car. There might also be another wire with large ring terminal on this post going to the charging system. Not sure about that. A diagram would really help. Other wires present are a heavy cable running from the OTHER large post to the starter, and 2 small wires that push on the 2 small posts.

 

The negative battery cable runs to the block generally. The body must also be grounded. I don't recall how Ford did it. There may be an extra terminal partway down the negative battery cable bolted to the body. If not. look for a small ground strap, maybe from the back of the engine to the firewall.

 

 

Edited July 19, 2020 by Bloo (see edit history)

[Voldad]

What you say about the wiring is true of mine. There is a ground from the firewall to the back of the engine block and I will go through your text to make sure the other is true as well. I wondered if the under dash mount radio working was a clue as to the probelm? BTW, I appreciate your response.

[Bloo]

Ok, on the back of the ignition switch, in your second image, top center is "yellow". This is the hot circuit coming from the battery. It starts at that ring terminal on the starter relay, hits the "BAT terminal on the voltage regulator,  goes through a connector (probably at the firewall), and then feeds the ignition switch (and the cigarette lighter and maybe another thing or 2, not important right now).

 

That yellow wire at the ignition switch should be hot all the time. Assuming your body is grounded, you should be able to verify easily with a test light or multimeter. Make sure you have a good clean ground on the dash or a bolt or something for your light or meter.

 

The center terminal is "accesssory" (blk-grn, blk-grn, org-wht). The lower right is ignition (blk-grn, red-grn, blk-grn).

 

Starting at "off", if you turn the key left, accessory should be hot.

 

If you turn the key to the right ("on") but not all the way to "start", BOTH "accessory" and "ignition" should be hot.

 

The remaining terminal (red-blu) is only hot when you are holding the key in the start position. Don't worry about that one just yet.

 

I'll bet you find something dead that should be alive. Let us know how it goes.

 

 

Edited July 19, 2020 by Bloo (see edit history)

[Voldad]

Thank you Bloo for the detailed answer. I will work through your suggestion and let you know.

[Rusty_OToole]

Start by checking the fuses. They could be blown corroded or missing. If the fuses are good a little work with a test light or multimeter will tell you if current is getting to the fuse panel or not. The wiring diagrams should be a big help.

[m-mman]

Bloo is correct and should get you started checking for general power. 

 

Testing FoMoCo gauges - (once you know power is getting to the key) Under the hood locate the temp sender. (screwed into the manifold it has a threaded stud ("L" shaped connector slips over) Remove wire - attach test light between this wire and ground. Turn key to ON. Wire should show a FLASHING 12 volts. (flashing just like a turn signal is important) Grounded this way, the temp gauge should go to 1/2 maybe 3/4(?) If you ground the temp wire completely the temp gauge should peg itself at HOT. 

The same process can be used for the gas gauge (check for flashing voltage and grounding should send needle to FULL) but it requires crawling under the car. 

 

If there is NO FLASHING voltage at the wires, then check: the power comes from the key (no fuse) to a rectangular shaped "flasher" thing connected to the back of the speedo unit. (Falcons are easy to remove) called a Constant Voltage Regulator (CVR) it sends power to both gauges (wires are easily seen) and then out to the sending units. The CVR works just like a turn signal flasher meaning that it must be grounded to function. The speedo unit must be grounded and the CVR needs to be bolted to the spedo unit. 

 

Good luck working through your project. 

[Voldad]

Thank you. I have fired the car and worked through all the leaks, coolant, trans, etc. All minor stuff. I Have been doing some shake down runs and haven’t had the chance to address the wiring issues yet but will update as soonas I do.