1979 f350 4x4 c6 .the truck was a 4speed i have been going through this truck sense march.

I got everything fixed except the reverse lights i assume because the tranny was changed to auto maybe the wire harness plug dont match or something.

what color are the wires for reverse lighting and does in come off the NSS ?
any other help would be great,

Also next to the speedo cable at the tranny is a outlet is this for reverse lights? or the tranny is from a later model? I bought it this way so i`m not sure

Thank`s

 

4 M/T backup lamp switch threads into the shift tower.

With A/T, the backup lamps are operated by the NSS (Neutral Safety Switch) that on 1978/79's, is located on the transmission.

 

So the NNS is bad? It works as far as not starting unless in park. If I have the switch and the reverse lights don't work what should I look at ? Thanks

 

Two different NSS's were used 1978/79. The one for the C6 (D8TZ-7A247-A / Motorcraft SW-1489) is different than the C4 (D8TZ-7A247-B / Motorcraft SW-1491).

 

Ok , I will verify I have the correct switch I would not be surprised if it's the wrong one. Thanks

 

My 79 used to be automatic. I switched to manual. It has been a while so I may be a little incorrect but here is what I remember. There is a plug with 4 wires in it that goes down to the transmission neutral safety switch. Two of the wires are to prevent the truck from starting if in gear and two wires are for the reverse lights. What I did was splice the two wires together that would stop the truck from starting. The other two wires just need wired the reverse switch that is on the shift tower of the manual transmission. They can go on either way as all the reverse switch does is make an electrical connection.

 

When the trucks came with a manual trans, there was a dummy plug used to by pass 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 by passes the NSS switch. Your truck will now startand the back-up lights will be permanently on.Now onto 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 yourback 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.

 

My truck ('75 250 4WD) was originally an auto, and the previous owner did a really nice 4 spd conversion. Column, trans tunnel, pedal assembly, etc. But he over looked the back up lights.


This is going to be really useful! Thanks for posting!

 

It has been right here all the time...https://www.ford-trucks.com/forums/1...then-some.html

With the truck being a 4 Spd the switch would be where the diagram says it would be.

Automatic trans 73-77 NSS and back up light switch/wiring on the column under the dash.

78/79 automatic NSS and back up light and wiring on the side of the trans.

 

QWell I am fooling with the back up lights. I don't have a plug with a jumper wire that I can see anywhere.
I do have a grey plug with four wires from the NSS. It plugs into a grey plug but has 6 wires. The white/purple stripe is doubled and the black with red stripe is doubled in the plug on the harness side. With the key on the w/p wire is hot I was able to jump a wire from there to the b/r wire and get back up Lights but with the harness plugged together I have no lights.
Is the NSS bad ??? It works as far as only starting in park.
Also when I was poking around with a jump wire I was able to turn the engine over by touching the w/p hot wire to blk and when I touch the last wire I here a little buzz by the dizzy maybe this is power to coil.
I think the tranny is out of a 73 Lincoln like the engine . Was the wire harness changed? I'll keep working on it with your help till I figure it out! Thanks Thanks

 

If you got back-up lights by jumpering at the harness, I would guess that yes, the switch is bad. The NSS is actually three switches in one, internally: one allows starting in Park, another allows starting in Neutral, and a third turns on the B/U lights in Reverse. Sounds like the B/U light part of the switch is bad even though the rest is still working.

 

 

IIRC, Red/Blue = starting circuit (from ignition switch, through the NSS, to the solenoid), Black/Red = reverse lights, and you've already determined that White/Purple = +12V in Run. The starting side of the NSS connects the two red/blue wires together. The reverse light side connects the white/purple to the black/red.

 

So the switch must be bad if I can jump the wires but no lights when plugged in.
I will order a switch from BG

I am onto the sig lighter and lower cab lights I need to find sockets , I found the 3 wire plug with the green/yellow stripe wire. I just got back from Nappa with the correct size male butt connector going to wire the dog lighter now.
Thanks

 

Yep, that's what I would conclude.