by lboast Wed Feb 03, 2021 8:11 pmI was looking for the back up light/neutral safety switch wiring in the shop service manual, and cant seem to locate the wiring for this switch on my 727 transmission. does anyone have a print they could share that shows the wiring for these 3 wires to/from this switch and where they go?
2 posters
back up light/neutral safety switch wiring
lboast- Number of posts : 112
Location : Prosser, Washington
Registration date : 2020-11-01
69- Number of posts : 446
Location : Germany, Nds
Registration date : 2016-10-18
Strange enough, my service manual (69) does not show the neutral safety switch (NSS) at all. But our's have one 
.
Wiring is from the starter relay to the center pin of the NSS. On the starter relay it works as follows:
orange is coming from the ignition switch ("start") to the starter relay. On the starter relay it (IIRC it is yellow) goes to the center pin of the NSS. The NSS must only provide a connection to ground to the starter relay (and the "start" position of the ignition switch), if gear is N or P.
The heavier gauge wires on the starter relay are from battery and to starter solenoid (this one is switched with the relay).
Backup lights is kind of tricky. Somewhen between 68 and 69 model years, they changed the setup from "switch at the gear selector" (behind dash) to trans mounted 3 pin switch.
The correct setup depends on the inner workings (rooster comb, to be correct) of the 727 in your truck. If yours has a three pin NSS, check if in R the two outer pins are connected (and of course no connection in all other gears). If so, according to the wiring diagram, start at the wiper switch + supply wire to one of the two pins (correct color: orange), the the other pin (black) to the backup lights with the other 5 wires to the rear of the truck (via dash, A pillar and so on...).
Hope this helps.
.Wiring is from the starter relay to the center pin of the NSS. On the starter relay it works as follows:
orange is coming from the ignition switch ("start") to the starter relay. On the starter relay it (IIRC it is yellow) goes to the center pin of the NSS. The NSS must only provide a connection to ground to the starter relay (and the "start" position of the ignition switch), if gear is N or P.
The heavier gauge wires on the starter relay are from battery and to starter solenoid (this one is switched with the relay).
Backup lights is kind of tricky. Somewhen between 68 and 69 model years, they changed the setup from "switch at the gear selector" (behind dash) to trans mounted 3 pin switch.
The correct setup depends on the inner workings (rooster comb, to be correct) of the 727 in your truck. If yours has a three pin NSS, check if in R the two outer pins are connected (and of course no connection in all other gears). If so, according to the wiring diagram, start at the wiper switch + supply wire to one of the two pins (correct color: orange), the the other pin (black) to the backup lights with the other 5 wires to the rear of the truck (via dash, A pillar and so on...).
Hope this helps.
lboast- Number of posts : 112
Location : Prosser, Washington
Registration date : 2020-11-01
Thank You. Ill check it our right after lunch. It surprises me that the big manual omits this circuit.
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