Back up light switch

[ponypastor]

Where is the back up light switch for the 429 SCJ with C-6? Back of the motor or on the tranny?

 

[Steve McMahan]

I thought the backup switch was mounted to a bracket on the tail shaft, and when the linkage was moved to reverse, it pushed on the switch to activate the backup light? That’s what I remember from my 1971 429scj a few decades ago.

 

[kcmash]

For a C-6 automatic it should be located in the shifter assembly.

kcmash

 

[secluff]

Hello Tim,
A forum member here had a similar problem finding neutral safety switches (NSS) at two different locations on different '71 429 C6 Mustangs. I checked catalog info back to 6/71, and only one NSS for a '71 Mustang C6 is shown, the DOZZ-7A247-B. I checked my Mercury info, and it shows the same part # for the '71 429 C6 Cougar. This switch is mounted at the manual shift arm location on the transmission.

But, this is a mass-produced vehicle from the '70s, so variances (either by design or accident) and "Things" happen. I hear the same from my GM and Mopar buddies.
I have heard from some original 429 C6 owners who found an NSS located at the shifter. This is the same neutral safety switch/harness as the FMX. If you don't see one located on the transmission, pull the shifter cover/bezel and look for a tape tag with one of the following engineering ID#s C8ZP-A, C9ZA-C, D, D1ZA-AA (Part # C9ZZ-7A247-C). D2ZZ-7A247-B replaced this switch. This switch and others that you see listed as after 12/1/71 incorporate an extra circuit and plug for the loved/hated seat belt/buzzer system. This extra plug can be left unplugged or removed. The '71 shop manual does have one reference to the neutral safety switch adjustment for Mustang and Cougar with FMX or C6 with 429 engine at the shifter!
This is one of those times I would sure like to corner an engineer from these era cars and say, What.....were you thinking!?

And just for the sake of confusion, my '71 M code C6 Mach 1s (Early build 9/21/70) and late build 7/28/71) both have neutral safety switches located on the transmission.

 

[Motorcity Mustang]

I have 7 429 Mustangs and have NSSs in the shifter and on the trans. Guessing they put them wherever that had parts coming from.

 

[secluff]

I have 7 429 Mustangs and have NSSs in the shifter and on the trans. Guessing they put them wherever that had parts coming from.

Mike, as the "Forum Member" I had dealt with, I'm glad you responded. I don't always mention names as sometimes members don't always want to get involved in some discussions.
As I had posted earlier, I went way back in some old fiche catalogs, and it only shows the one neutral safety switch for all C6 applications, which is the transmission-mounted version. Same as my '71 M code C6 Mach 1s. When you posted the tag number D1ZA-AA (FMX engineering number) to me, I knew something weird was happening since it was on more than one of your cars. The ONLY time I have ever seen anything from Ford indicating there might be a difference in switch locations was the mention in the '71 shop manual of adjusting the switch at the shifter for FMX and C6 429 cars!
I have devoted Mopar friends who tell me Chrysler was even worse with these types of issues. I don't know; I've dealt with these numbers for many years and still get shocked at some things I see.

 

[Retired2014]

My (late December 71 built) 72 Mach with a C6 incorporates the reverse light in with the NSS side mounted to the tranny.

 

[Motorcity Mustang]

Mike, as the "Forum Member" I had dealt with, I'm glad you responded. I don't always mention names as sometimes members don't always want to get involved in some discussions.
As I had posted earlier, I went way back in some old fiche catalogs, and it only shows the one neutral safety switch for all C6 applications, which is the transmission-mounted version. Same as my '71 M code C6 Mach 1s. When you posted the tag number D1ZA-AA (FMX engineering number) to me, I knew something weird was happening since it was on more than one of your cars. The ONLY time I have ever seen anything from Ford indicating there might be a difference in switch locations was the mention in the '71 shop manual of adjusting the switch at the shifter for FMX and C6 429 cars!
I have devoted Mopar friends who tell me Chrysler was even worse with these types of issues. I don't know; I've dealt with these numbers for many years and still get shocked at some things I see.

I find that nothing amazes me anymore on the assembly of these cars in the 60s and 70s! I have one that still has the original Autolite Shocks, Ford Mufflers, etc on it and have been using that as a reference, but even that has little odd differences to others.

 

[ponypastor]

I find that nothing amazes me anymore on the assembly of these cars in the 60s and 70s! I have one that still has the original Autolite Shocks, Ford Mufflers, etc on it and have been using that as a reference, but even that has little odd differences to others.

Thank you to all for you input and suggestions. I search for the back-up light switch on the driver side of the tranny and under the shifter bezel by the NSS, but found nothing. Any other suggestions?

 

[mjseakan]

This might be a silly question, but do the backup lights work? If they don't maybe the switch is missing and that's why you can't find it. If they do work then I can't help you.
Mike

 

[ponypastor]

Issue resolved: I approached the problem of no back-up lights with the (unexamined) assumption that the C-6 tranny contained both a Neutral Safety Switch AND a separate back-up light switch. My assumption was incorrect. The backup light switch is part and parcel of the NSS, not a separate component.

So, when I changed out the #2 fuse (thanks to advice from Randy) to fix another lighting problem, the back-up lights immediately worked. Problem solved. Thank you to all who offered suggestions to resolve the problem. Cheers.

 

[carguy47]

I could be mistaken, however I thought it was within the neutral safety harness, IN the shifter.

 

[mrgmhale]

Hello Tim,
A forum member here had a similar problem finding neutral safety switches (NSS) at two different locations on different '71 429 C6 Mustangs. I checked catalog info back to 6/71, and only one NSS for a '71 Mustang C6 is shown, the DOZZ-7A247-B. I checked my Mercury info, and it shows the same part # for the '71 429 C6 Cougar. This switch is mounted at the manual shift arm location on the transmission.

But, this is a mass-produced vehicle from the '70s, so variances (either by design or accident) and "Things" happen. I hear the same from my GM and Mopar buddies.
I have heard from some original 429 C6 owners who found an NSS located at the shifter. This is the same neutral safety switch/harness as the FMX. If you don't see one located on the transmission, pull the shifter cover/bezel and look for a tape tag with one of the following engineering ID#s C8ZP-A, C9ZA-C, D, D1ZA-AA (Part # C9ZZ-7A247-C). D2ZZ-7A247-B replaced this switch. This switch and others that you see listed as after 12/1/71 incorporate an extra circuit and plug for the loved/hated seat belt/buzzer system. This extra plug can be left unplugged or removed. The '71 shop manual does have one reference to the neutral safety switch adjustment for Mustang and Cougar with FMX or C6 with 429 engine at the shifter!
This is one of those times I would sure like to corner an engineer from these era cars and say, What.....were you thinking!?

And just for the sake of confusion, my '71 M code C6 Mach 1s (Early build 9/21/70) and late build 7/28/71) both have neutral safety switches located on the transmission.

I have gone through this morass fairly recently for our 1973 Mach 1, and managed to splice in the NSS/Backup Lamp/Seat Bet Interlock switch from an AOD into the harness for a C4 NSS/BUL switch unit.. For 71 and 72 the NSS and Backup Lamp Switch (BULS) is a unitized unit that is bolted onto the driver side of the auto tranny, regardless of it being a C4, FMX or C6. For 1973 there is a are two pairs of wires for the NSS and BULS, one pair per circuit.

For 1973 the NSS/BULS also has a Seatbelt Interlock switch (SBI), although those Interlock circuits were largely bypassed once it was found how ineffective and troublesome they were. Regardless, the 1973 NSS/BULS/SBI unit has three pairs of wires running to it, one pair of which can be left disconnected due to the SBI circuit being disabled.

I do not have the part numbers for the 71-72 and 73 units, but in posts prior to my response it looks like you have plenty to sink your teeth into. What I offer are some schematics I put together for another enthusiast who was running into wiring issues.

As an aside. for our 73 Mach 1 I replaced the original C4 with an AOD. The AOD has an integrated NSS/BUL switch that is plugged into a connecter that is part of the AOD assembly, totally different from the C4/FMX/C6 switch system design. I have a video showing how I altered the original NSS/BUL/SBI interlock harness (not the vehicle wiring harness) to accommodate the AOD switch unit. That link it here:



It looks like you do have an auto tranny. If you actually have a manual tranny let me know as there are some differences in the switch(es) used, and the way the wiring circuit is put together.
Please feel free to reach out in the event you have more questions, concerns, comments, etc. Also, the 71 and 72 wiring ought to be the same, but I included snippet files for both years just in case there is a difference.

 

[Gustavo]

Hello, I know this issue has been resolved but I don't know how to make a new post,
So I checked the nss switch, looks like it works, twist it shuts off power to the black w/ purple wire (BU lights)
But when I disconnect the nss switch from the harness and jump the hot wire ( Red/ Grey)
I don't get nothing, but the wire do become hot when I disconnect the BU lamps from the socket, once I connect them no light but now hear me out,
I get 12v from the battery and connect it directly to the Black W/ purple and voila, they turn on, it's only when I jump it from the 1 of the 4 wires that's is hot, they won't turn on but it is sending voltage through the wire, it just cancel each other out when the bulbs are connected.
Supposedly I read it can be a bad wire but if it was so, me sending 12v from the battery not turn it on ? Unless the hot wire is bad in some spots ??
I'm in a pickle and any help will be greatly appreciated

 

[midlife]

The main power line for back ups is white/purple and output is black/red. I think you jumpered the wrong wires. One should be male and the other female.