no back up lights
Thread Starter
|
Tuned
Joined: Dec 2008
Posts: 269
Likes: 1
From: Paradise, CA
no back up lights
While testing the wiring for trailer lights I realized my reverse lights on my 79 F150 400/C6 weren't working. All other lights work. I found that the wiring for my neutral safety switch had cooked from the exhaust (explaining the smell I recently noticed) so I cut the wires near the switch and ran wires up to the engine compartment, this time routing them clear of header heat. So, I still don't have reverse lights. Am I wrong about the neutral safety switch controlling the reverse lights? Maybe the switch is burned out and needs to be replaced but I'm looking for the free repair this time. I need to buy new rims, tires, and springs for my rear end upgrade and that leaves no money for anything else. Thanks for any help
Senior User
Joined: Dec 2010
Posts: 117
Likes: 0
From: Vancouver, Canada
i had same problem with my 78 ( 400 C6 ) and i replaced my NSS because i could start my truck in any gear and i had also read that the NSS controls the reverse lights...unfortunately they still dont work.
Cargo Master
Joined: May 2009
Posts: 2,587
Likes: 47
From: Eagle River, AK
There are definitely a few things that can cause this, but you guys seem to be on the right track.
Check the fuse
Check the continuity within the NSS at the plug when the shifter is in reverse. I have also read somewhere that some people have pulled the NSS apart and cleaned the contacts inside the NSS with good results, but I looked and can not find it again.
Check the bulbs and sockets (the sockets can look good, but be bad. I had to replace a couple on my truck even thought they looked good)
There is a plug behind the rear bumper that gets some heavy corrosion sometimes. Check it, clean it or replace it if necessary.
Check the grounds, make sure all connections are clean and tight. Battery to engine, engine to frame and cab, cab to frame, bed to frame.
Check the fuse
Check the continuity within the NSS at the plug when the shifter is in reverse. I have also read somewhere that some people have pulled the NSS apart and cleaned the contacts inside the NSS with good results, but I looked and can not find it again.
Check the bulbs and sockets (the sockets can look good, but be bad. I had to replace a couple on my truck even thought they looked good)
There is a plug behind the rear bumper that gets some heavy corrosion sometimes. Check it, clean it or replace it if necessary.
Check the grounds, make sure all connections are clean and tight. Battery to engine, engine to frame and cab, cab to frame, bed to frame.
Fleet Owner
Joined: Dec 2009
Posts: 20,678
Likes: 83
From: NorCal
74-78 Wiring Diagrams
For your troubleshooting pleasure.....Here you go:
74-78 Wiring Diagram Pt1
74-78 Wiring Diagram Pt2
Zoom in and it should be readable.
74-78 Wiring Diagram Pt1
74-78 Wiring Diagram Pt2
Zoom in and it should be readable.
Trending Topics
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
Top 10 Fords at 2026 Carlisle Ford Nationals
Joe Kucinski
3 Best / 3 Worst Parts of Modern Ford Ownership
Brett Foote
10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches
Pouria Savadkouei
Every 2026 Ford Engine Explained
Brett Foote
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Thread Starter
|
Tuned
Joined: Dec 2008
Posts: 269
Likes: 1
From: Paradise, CA
Thanks for all the replies. I had already the bed harness and it ohms out. I also checked the fuses and I don't have any blown fuses and from my shop manual it said the same fuse controlled other lights. Unfortunately the shop manual doesn't speak much about the NSS other then adjusting it.....not fixing it or any other electrical problem associated with it. I need to do more investigating. I ran out of day light after I fixed the burnt wires and haven't had time to take another look. I've checked and the lights don't come on in any gear, but the thing is specific about which gear it is in to start. I would bet the switch burned out. Maybe I can find one at the junk yard. I need to get a driveshaft so I'll already be under a rig for that. Are they hard to change and adjust?
Cargo Master
Joined: May 2009
Posts: 2,587
Likes: 47
From: Eagle River, AK
If your not in a hurry, I get home from work Thursday evening and I think I have a good NSS off of an older C4. I think the body of the NSS is the same, it just has a different plug, You could splice your plug onto it. I know I will not be using it, I could have it in the mail to you on Friday. If your interested, shoot me a PM.
Can anyone confirm that the main body, mounting and function is the same for the NSS's for the C6 and C4?
If it'll work for you, it's yours.
EDIT - The one I have at home is a MOTORCRAFT Part #SW877 {#C9ZZ7A247B}
Can anyone confirm that the main body, mounting and function is the same for the NSS's for the C6 and C4?
If it'll work for you, it's yours.
EDIT - The one I have at home is a MOTORCRAFT Part #SW877 {#C9ZZ7A247B}
Moderator
Joined: Nov 2007
Posts: 22,415
Likes: 92
From: Denver Metro Area, CO
I have no idea what else it may fit....
Cargo Master
Joined: May 2009
Posts: 2,587
Likes: 47
From: Eagle River, AK
Correct. I had it on a C4 behind a 302 in a 2wd 68 F100. The engine and tranny were not the originals, so I really do not know what year everything was. But I do know it looks similar to the one listed for the 79's with a C6 other than the plug.
New User
Joined: Sep 2011
Posts: 7
Likes: 0
From: San Diego
Had the same problem with a truck (96 f150) where I used to work. The NSS can't really be repaired (at least that one couldn't) and autozone doesn't sell them because its a dealer part and an expensive one at that. But its safe to say thats your issue.
Thread
Thread Starter
Forum
Replies
Last Post
Trent Racer
1987 - 1996 F150 & Larger F-Series Trucks
3
Aug 10, 2015 10:25 PM
