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Posted By Discussion Topic: '40 Ford wiring schematic question -- page: 1 2 3     Carcheologist 05-19-2021 @ 7:30 AM reply profile send p.m. New Member Posts: 132 Joined: Jan 2016 Does anyone have a clear COLOR copy of the '40 Deluxe wiring schematic? I noticed a pair of wires ;under the dash that were not connected to anything - they are joined together by a ring terminal and looked to be either faded green with black tracer or faded yellow with black tracer. They split off from the main underdash harness bundle slightly to the right of the instrument cluster. I have checked the schematics available and can't seem to identify the wires by color or where they should be connected. Appreciate any help. Mike in Texas 40 Coupe 05-20-2021 @ 5:39 AM reply profile send p.m. Senior Posts: 1674 Joined: Oct 2009 All of the schematics and wiring diagrams for the early Fords are black and white. It's going to be difficult to find the purpose of the wires. As you can see the wire color changes over time. Check under the dash in the area of the wires and look for a device that is missing wires such as the dash light rheostat. kubes40 05-20-2021 @ 7:12 AM reply profile send p.m. Senior Posts: 3394 Joined: Oct 2009 I can only hazard a guess but suspect, as 40coupe has responded, the two wires are for the rheostat. The rheostat, when aged, either stops working completely or works poorly and causes the dash lights to be dimmer than their "normal" dim. Are there wires going to the rheostat at this time? I might suggest, based on your description of your harness, that you replace it. Dennis Carpenter offers a nice quality harness with an easy to follow schematic at a very fair price. Old harnesses scare me. Mike "Kube" Kubarth Carcheologist 05-20-2021 @ 7:36 AM reply profile send p.m. New Member Posts: 132 Joined: Jan 2016 Thanks for all the replies. Maybe a little clarification would help. The harness was replaced when we restored the car 25 years ago, so it's still very flexible and not old and brittle - you can make out most of the wire colors just fine too. Secondly, the wires going to the rheostat/gauge panel dimmer are blue; both are connected to the dimmer and the dimmer works correctly. The wires I'm seeing are either faded green/black tracer or faded yellow/black tracer and are joined together with a common ring terminal, just can't identify where they come from or where they should connect. P. S. Kube, got your '40 book on Tuesday and it's a real treasure! I'm really enjoying knowing more about'40 Fords. As my handle implies, I'm a nut for automotive minutiae and your book is on target. Great job! kubes40 05-20-2021 @ 7:53 AM reply profile send p.m. Senior Posts: 3394 Joined: Oct 2009 Thanks for the kind words re the book. Much obliged to ya. Might you be able to provide a photo of the wires and their location? Can you peal back the woven covering "down the line" a bit to see the true (non-faded) colors of the wires? Mike "Kube" Kubarth This message was edited by kubes40 on 5-20-21 @ 7:53 AM TomO 05-20-2021 @ 8:29 AM reply profile send p.m. Senior Posts: 7250 Joined: Oct 2009 I would start by checking which features work and don't work. If all of the features work, then I would look to see if additional wires or features like turn signals were added and these wires are not needed.. I don't remember any green wire with a black tracer, but there are a few yellow wires with black tracer under the dash. Tom Carcheologist 05-20-2021 @ 9:51 AM reply profile send p.m. New Member Posts: 132 Joined: Jan 2016 Photo of mystery wires attached. As mentioned, they look to me like yellow with a black tracer and they are joined together with a common ring terminal (came that way on the harness). Also, they are "HOT" when the ignition switch is flipped on. I haven't noticed anything electrically on the car that doesn't work properly and they are too short to reach the circuit breaker. Other thoughts? JayChicago 05-20-2021 @ 10:16 AM reply profile send p.m. Member Posts: 480 Joined: Jan 2016 Heres my guess: I think TomO's idea makes sense. Since this is a replacement harness, could have come with additional wires that may be needed on some customer's cars. Feed for a radio? Since this is hot with ignition, looks like that ring terminal was also serving as a splice point in the harness. Second wire goes on the feed other thing(s). Carcheologist 05-20-2021 @ 11:06 AM reply profile send p.m. New Member Posts: 132 Joined: Jan 2016 JayChicago, Thanks for the feedback. I assumed that my replacement harness was a "faithful" reproduction for the '40 Ford when I bought it 20+ years ago, but who knows. My radio is connected to another power source, but need to check where it gets its power from. I still think something else is going on that I haven't grasped yet. I have combed the available '40 wiring schematics but don't see anything yet that gives me any clue as to where it should reside. - I'll keep looking. Carcheologist 05-20-2021 @ 11:30 AM reply profile send p.m. New Member Posts: 132 Joined: Jan 2016 After another examination under the dash, I noticed that these 2 wires exit the dash loom directly above the factory punched hole through the lower ledge of the instrument panel (where the accessory heater switch Kube talks about in the '40 book). The joined wires are long enough to reach the switch. Could they be the main power source for the heater control switch?

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