• 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
Safety neutral switch FMX tranny
#1
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.
  Reply
#2
The neutral safety switch on the FMX is part of the shifter as are the reverse lights. Here are some pics of an FMX shifter.....


[Image: FMX-shifter-1.jpg]

[Image: FMX-shifter-2.jpg]

73 Grandé H Code. Headman long tube headers, T-5 Transmission, 3.70 Traclok, Lowered 1" all around, Aussie 2v heads w/ 2.19 intake, 1.71 exhaust, screw in studs, full roller cam 608/612 lift 280/281 duration LSA 112, Quick Fuel 750 CFM double pumper, AirGap intake.

- Jason


[Image: 082-hot-rod-power-tour-2017-1970-1970s.jpg]
  Reply
#3
Thanks for the pictures.
My shifter does not contain the neutral switch that's why I am at a loss.
I crawled underneath the car looking for a safety switch on the tranny and could not see one.
  Reply
#4
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.



“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
  Reply
#5
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??

73 Grandé H Code. Headman long tube headers, T-5 Transmission, 3.70 Traclok, Lowered 1" all around, Aussie 2v heads w/ 2.19 intake, 1.71 exhaust, screw in studs, full roller cam 608/612 lift 280/281 duration LSA 112, Quick Fuel 750 CFM double pumper, AirGap intake.

- Jason


[Image: 082-hot-rod-power-tour-2017-1970-1970s.jpg]
  Reply
#6
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.


  Reply
#7
(04-08-2019, 11:37 AM)Don C Wrote: 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.

[Image: attachment.php?thumbnail=6460]
  Reply
#8
(04-08-2019, 11:49 AM)Hemikiller Wrote: 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.
  Reply
#9
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.



“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
  Reply
#10
(04-08-2019, 11:47 AM)73pony Wrote: 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.
  Reply
Share Thread:  




Users browsing this thread: 1 Guest(s)