Extra wire.
 

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Hi, I have a extra black wire with a mounting ring on the end in my dash. 65 standard cab. I can account for the fuel gauge wires, and the oil light wires, but not the black one. The truck is new to me. The PO had wedged the black wire between the fuel gauge and the mounting housing. this black wire a ground wire? If so, then where does it mount ? Thanks, fatdan.

Where does the other end go? What color are the two other wires its pictured with?

If it's black with no stripe, there are only three of them in the truck of similar gauge: #38 / 38A connect the starter relay to the alternator Battery terminal and #57 / 57A which connect the headlights to ground at the regulator, obviously neither of which are near the dash.

So I suspect that wire is #98 which is shown as the 20 gauge resistor wire that goes from the ignition switch A terminal to the 7-pin connector in the firewall, and changes to #904 green with red stripe to the regulator S terminal; and also connects to #85 yellow with black stripe which goes to the charge indicator light.

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Ok, let"s start over with a better picture. The blue with red tracer goes to temp gauge in round cluster. The white with red tracer and the green wire goes to oil press gauge that is a separate gauge from the cluster. The black wire with the eyelet comes from the wiring harness. For a side note, the PO installed a vintage air under dash a/c unit, the a/c wiring did away with the heater control switch. Could there be a connection between the black wire and the heater control switch?

Well then, can you answer John's question about where the other end of the wire goes?

No, not at this time. I'll see if I can follow it.

That wire is part of the C5TZ 10A665-A, C or E Charge Indicator Feed harness if you have a 2WD and -B or -D if you have a 4WD. It provides a ground for the backlights of the outboard auxiliary gauges. The Custom Cab trucks mount the auxiliary gauges in a plastic gauge cluster, so they had to have a way to provide a separate ground. Notice that the bulb sockets in the auxiliary gauges are plastic and have both a power supply (blue w/red stripe) and a black ground wire whereas the other gauge cluster backlights use a single blue w/red stripe wire and a metal socket to provide a path for the ground directly to the back of the gauge cluster. Attach it to the back of the gauge cluster or use the same attach point as the cluster ground at the steering column support.

Wire harness is the same for Standard and Custom Cab but the Standard cab used a metal cluster bezel so no separate ground wire was required for the gauges. For the plastic cluster in the 1965/66 Custom Cab they use a separate ground wire for the housing to ground it, but the Amp and Oil gauges are just hanging out there in the plastic so they require their own ground. 81B in the application information indicates Custom Cab.

C5TB-10B992-A - Instrument Cluster Ground Wire - 8" - 1965/67 F100/250 (81B-4 x 2) - 1 each
or
C6TB-10B992-A

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The harness itself prevents the metal gauge face from providing a ground as the bulb sockets are plastic. As you mentioned Ford didn't design 2 different harnesses for the Custom and Standard cabs.

Well,that makes sense, I think that's the reason the p o had the black wire wedged between the gauge and housing. I want to thank everybody for taking the time to help me. Someday I hope to be able to help others that need help. Thanks fatdan.

Dan:
Here's where that wire went on my 66.
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I haven't spent a lot of time with it, but on my 1966 F250 4x4s they have the metal bezels since all F250 4x4s only had that style of bezel. If I remove the 8 screws from the bezel and let it flop out away from the dash til the speedometer cable stops it and just let it hang there in space and turn on the truck there sure are some things that don't work right. If I put one screw back in or hook up a jumper wire with alligator clips from it to the metal dash then it goes back to normal. I think the ICVR is needing to be grounded thru the cluster bezel, but I have not tried grounding just it yet.

Chad

http://fordification.info/tech/image...ringMaster.jpg This wiring diagram shows a ground for the constant voltage unit for custom cabs only.

Shouldn't require a separate ground wire since Standard Cab grounds the metal bezel to the metal dash so it is not needed as a separate wire. The ICVR needs a ground, no question about that. It only has an input (IGN connection) and output voltage on the two prongs so the ground for it comes from the housing and bracket and whatever it attaches to being grounded.

Chad