Reverse lights question - 73 Mustang Coupe

[70sElvis]

Forgive my stupid question but I have no reverse lights. The fuse is good, tail-lights work so wires should be good going to the back and the NSS works (as far as not allowing cranking in gear). I know there are two wires for the reverse lights - white-purple and I believe black-purple at the plug. Which (if not both) should have power to them? Test both and have nothing.

 

[Steve McMahan]

Try this wiring diagram. Start at fuse f1 and go from there:

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You should have power on both side of the fuse, then check the switch, both sides. The wiring goes from the dash, into the engine compartment, and down to the transmission, as I remember. Let us know what you find. Steve

P.S. And your question isn’t stupid.

 

[midlife]

White/purple has incoming power to the NSS. It shares the fuse with the factory radio, turn signal flasher can, washer pump.

 

[RD-72]

I had the same issue on my car

For my c4 automatic transmission, it was a faulty neutral safety switch
attached is a repop picture for reference purposes I found on the web
it attaches to the transmission and runs up the firewall and plugs in
good luck

 

[CarCrazy73]

As RD-72 stated it probably is a faulty or worn out neutral switch, which was my case on one of my ‘73’s.

 

[mrgmhale]

Just a Heads Up, but first the preceding info provided by some of our other colleagues is all dead on. But, there is something I want to alert you to. The Neutral Safety Switch (NSS) is integral to the Back Up Light (BUL) switch, as well as the Seat Belt Interlock (SBI) system. The Seat Belt Interlock systems back in the the 1973 period all sucked, to say the least. The legislation requiring them was reversed due to a popular public outcry, and every vehicle I have seen from back when they had the Interlock systems have had it disabled (legally). I mention this because the NSS/BUL/SBI switch for 1973 Mustangs has 6 wires on its lead wires, whereas for 1971 - 1972 there are only 4 wires (NSS and BUL). I know I was able to get the 6 wire NSS/BUL/SBI switch when my Backup Lights stopped working. But it took some hunting around. I have never tried to see if the 1971-1972 NSS/BUL will connect and work properly in a 1973 Mustang. But, even if the connectors do not fit, I see no reason the proper wires from the vehicle harness could not be matched up and spliced into the lead wires on the 4 wire switch.

I see Steve McMahan has already provided you a nice schematic snippet, and MidLife provided some clarification on the NSS wiring. I have a colorized and annotated schematic that may be of additional help. But, it is too large to attach to this post. If you are interested in getting the PDF snippet, which I have annotated to help clarify some parts of the wiring (where I break out Circuits 32A and 32B from the general Circuit #32 for example) just email me at [email protected].

 

[70sElvis]

Thanks guys! As always, yall are awesome! It will be Saturday before I can work on it again but I will definitely report back my findings. And hopefully of a picture of reverse lights on.

 

[mrgmhale]

Attached are the Neutral Safety and Backup Light Switch schematic snippets for 1972 (and likely 1971 also). Connector C-406 in the 1972 schematic looks like it is the same as used for the NSS/BUL wires from the 1973 schematic for NSS/BUL switch Connector C-20.

For 1973 the added two wires for the 1973 Seatbelt Interlock use a different connector (Circuits 469 & 520 pass through Connector C-414).

The attached 1972 (and 1971) NSS/BUL Switch schematic snippet is small enough to attach to this post. The 1973 snippet I have is too large to attach to this post, but is still available if you would like it also ([email protected]).

 

[73CobraJet]

As RD-72 stated it probably is a faulty or worn out neutral switch, which was my case on one of my ‘73’s.

OK another "dumb question" from me now; The reverse lights are controlled by the neutral safety switch?. I thought it would be two different switches. My back up lights do not either. SMH!!

 

[midlife]

The reverse lights and NSS are combined in a single switch assembly.

 

[70sElvis]

Well whomever said it was power wires cut under the dash, you were right. Also whomever said the NSS switch was bad, you were already correct. Plus the people who said it was probably wiring going to be the bulbs, bingo! Correct also. Did a lot of wiring/testing over the weekend and discovered all of that. I have a new NSS on its way and digging under the dash for my cut white/purple wire. Thanks guys. I see light (no pun intended) at the end of the tunnel.

 

[70sElvis]

Thanks guys.. All good now. On to the next thing.

 

[mrgmhale]

Thanks guys.. All good now. On to the next thing.

Very cool. What a mess to try to figure out and correct, eh? I love working on electrical system. I hate coming in behind someone who fancied themselves qualified to monkey with electrical systems. Having said that, I never minded coming behind someone else's work if they knew and understood what they were doing. There are several folks within this forum I would be happy to come into an electrical system after they did prior work, as I know it would have been done purposefully and correctly. There are actually some legends who live amongst us! Yes, MidLife, you are one of those folks... heh heh...

 

[midlife]

Naw, I'm only a legend in your and my mind...*G*