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1979 F250 Custom, 4WD, C6 automatic, 351M (now 400), no air, no cruise. Cannot find this on my laminated color wiring diagram and have cruised through my CD, and do not see where this could mate to. Everything else appears to be accounted for. Comes out where main harness does upper left cowl. White with purple stripe and black with red stripe wires to the two female plug. Thank you in advance,
Looks like the horn relay plug maybe. "upper left cowl" is this drivers side or passenger side?
edit: never mind horn relay has three connections so it's not that.
Don’t know about the white with purple, but the black with red and the shape of the connector indicates back up lamps for a column shift manual trans truck.
At least that’s what they look like on older models but in these later years, I’m not sure if that was used.
But look for different back up lamp switches and see if any of them match the wire colors.
There are a lot of connectors and sections of wire that do not get used on every model, however, they are included in the main wiring harness to simplify manufacturing.
your automatic trans back up lamp switch is probably on the column, but under the dash where the neutral safety switch is. Correct?
Don’t know about the white with purple, but the black with red and the shape of the connector indicates back up lamps for a column shift manual trans truck.
At least that’s what they look like on older models but in these later years, I’m not sure if that was used.
But look for different back up lamp switches and see if any of them match the wire colors.
There are a lot of connectors and sections of wire that do not get used on every model, however, they are included in the main wiring harness to simplify manufacturing.
your automatic trans back up lamp switch is probably on the column, but under the dash where the neutral safety switch is. Correct?
Correct. Yes, there are at least two other surplus connectors I have identified in the harnesses. Thank you.
Dvrs side upper cowl? As in on the inner fenderwell area by the electronic ign (brain box) inside the engine compartment? Does your reverse lights work now? FTE talk about it. "When the trucks came with a manual trans, there was a dummy plug used to bypass the NSS switch. I've never been able to come up with a part number for the dummy plug. To bypass the automatic set up: Unplug the switch and discard or ignore. There are four wires in the harness plug, two each, red w/ blue trace and black w/ red trace. Run a jumper between the red/blue and red/blue, do the same for the black/red. That completely bypasses the NSS switch. Your truck will now start and the back-up lights will be permanently on.
Now on to the backup lights. In the engine compartment is a little U shaped jumper wire. It'll be located on the drivers side splash pan, just in front of the firewall where the wiring harness comes through. Unplug the little jumper, this will shut off the back up lights. There should be a back up light switch on the trans cover. Run two wires from the switch to the two wires that were jumped. This will get your back up lights working again. Just a note, you could make a jumper plug out of the NSS. Cut the switch off the harness and splice the two pairs of wires. I just hate to cut these switches up. New, they're getting pricey. Here's the little jumper in the engine compartment. EDIT: If you don't care about the back up lights, just jumper the red w/ blue trace wires. This will by pass the NSS but the back up lights won't work."
