Safety neutral switch FMX tranny

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dave1956

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Joined
Apr 29, 2018
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Location
Mississauga, Ontario
My Car
1973 Mustang Sportroof
[url=https://ibb.co/R9pkSdL][img]https://i.ibb.co/Y37FWwv/thumbnail-1971-Mustang-1.jpg[/img][/url]
Hello All,

I have a 71 Mustang sportroof with a 302 and FMX auto tranny. 

My problem is the back up lights don't work, there is no safety neutral switch in the floor shifter and I cannot locate one on the transmission.

The car starts in park & neutral.

I am at a loss as to where the safety neutral switch is if there is one on the car at all?

Any idea's would be appreciated.

 
Have you tried to start it with it in drive? It's possible someone jumpered the wires for the NSS. Be careful when you try it, keep your foot on the brake.

Did your car originally come with a C4? That would explain the lack of an NSS.

 
That was going to be my guess as well Don. If you look under the car try to find the wires (red with light blue stripe) these are the NSS wires (if tied together they jumpered the NSS). Back up lights are white - purple for the hot side and black - pink for the load side. There should also be a brown wire in the bundle that was the hot lead for the lights on the shifter indicator, and I'm not 100% on a 71 but the seatbelt warning lights on a 73 are light green for the hot side and purple - white hash for the load side. Hope this helps, maybe if you can locate the wires at least you can follow them to somewhere??

 
Coming out of the main harness behind the engine will be one or two square rubber plugs. One is for the NSS, which will have four wires. Two red w/light blue stripe (NSS) and two black w/red stripe (B/U lamps). Since the 302 cars only automatic option was a C-4 and you have an FMX with a missing NSS, then most likely you'll find that the plugs have been jumpered.

Easiest fix would be to replace you shifter with one from an FMX equipped car with the NSS.

 
Have you tried to start it with it in drive? It's possible someone jumpered the wires for the NSS. Be careful when you try it, keep your foot on the brake.

Did your car originally come with a C4? That would explain the lack of an NSS.
No I have not tried to start it in drive but I will later when I get home from work.

I purchased this car last fall and started working on her over the winter. I thought it had a C4 tranny (based on the what the previous owner told me but when I dropped the oil pan I found out it was a FMX (based on this picture) and I replaced the shifter bushings and there was no NSS in the housing. I crawled under the car and had a good look to see if I could find the NSS attached to the tranny but came up with nothing. The reason I am asking is that my back up lights don't work and I started to explore the reason they don't. I am at a complete loss now.

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Coming out of the main harness behind the engine will be one or two square rubber plugs. One is for the NSS, which will have four wires. Two red w/light blue stripe (NSS) and two black w/red stripe (B/U lamps). Since the 302 cars only automatic option was a C-4 and you have an FMX with a missing NSS, then most likely you'll find that the plugs have been jumpered.

Easiest fix would be to replace you shifter with one from an FMX equipped car with the NSS.
Thanks Hemikiller for the reply. 

I did notice a square rubber plug behind the engine but there is nothing plugged into it nor does it have wires to jump it (I will verify the wire colour codes to this plug). 

As I mentioned in another post this all came about because I have no back up lights. I replaced the shifter bushings and there was no NSS in the bucket and I crawled underneath and check for a NSS and nothing  - I am at a complete loss. Don C. suggested I try starting her in drive.

 
Because the backup lights also work off the NSS, and because your car originally had a C4, it's almost a certainty that your car does not have an NSS.

I don't believe that the FMX ever came with provisions for a transmission mounted NSS, they were all mounted on either the steering column (for column shifters) or the floor shifter.

 
That was going to be my guess as well Don. If you look under the car try to find the wires (red with light blue stripe) these are the NSS wires (if tied together they jumpered the NSS). Back up lights are white - purple for the hot side and black - pink for the load side. There should also be a brown wire in the bundle that was the hot lead for the lights on the shifter indicator, and I'm not 100% on a 71 but the seatbelt warning lights on a 73 are light green for the hot side and purple - white hash for the load side. Hope this helps, maybe if you can locate the wires at least you can follow them to somewhere??
Thanks for the suggestion on tracing the wires, which I will do on the weekend (this should be fun).

I will let you know what I find.

 
I found the plug (only one). They contain two red/light blue wires & one black/pink & one white (off white it seems like). The car starts in P-R-D-1-2.

Seems like I am missing the NSS.

I would appreciate and comments, advise & help.

Thanks,

 
Coming out of the main harness behind the engine will be one or two square rubber plugs. One is for the NSS, which will have four wires. Two red w/light blue stripe (NSS) and two black w/red stripe (B/U lamps). Since the 302 cars only automatic option was a C-4 and you have an FMX with a missing NSS, then most likely you'll find that the plugs have been jumpered.

Easiest fix would be to replace you shifter with one from an FMX equipped car with the NSS.
 
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I found the plug (only one). They contain two red/light blue wires & one black/pink & one white (off white it seems like). The car starts in P-R-D-1-2.

Seems like I am missing the NSS. I think the part number for the NSS is: D2ZZ-7247-B?

NSS has two plug connections, 1 is blue & the other is black. I can see the black plug connection mating with the one on my car but what is the blue plug connection for?

I would appreciate and comments, advise & help.

Thanks

 
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71 FMX would use the C9ZZ-7A247-C aka Motorcraft SW-903 switch. You could also use the later D2ZZ-7A247-B switch you posted, the extra connector is for the seat belt warning system, which can be left unplugged.

 
The white/purple stripe wire is the power feed for the backup lights. The black/purple stripe wire runs from the backup light switch to the backup lights.

The red/light blue stripe wires are for the NSS, one leg comes from the ignition switch, the other goes to the "S" terminal on the starter solenoid.

 
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71 FMX would use the C9ZZ-7A247-C aka Motorcraft SW-903 switch. You could also use the later D2ZZ-7A247-B switch you posted, the extra connector is for the seat belt warning system, which can be left unplugged.
Thank you for your reply & assistance.

I managed to find a NSS which I hope will fix my problems.

 
Sorry that I can’t add much to this post except to verify what plug is used on my original 3 speed manual. It has a four pin plug at the back of the engine centered on the fire wall so maybe that might help eliminate looking for a plug in the wrong place.

but I do have a question where to place the backup switch on the three speed manual

I have a bracket and assume it mounts to the shifter...If anyone Has a pic of where that switch mounts I’d appreciate it. Thanks!!!

 
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