Jim Smart
December 12, 2013

Classic Mustangs tend to leave unsuspecting motorists stranded because the engine won't turn over, leaving owners at the mercy of repair shops that try to sell them a battery, starter, solenoid, or even a charging system when the only problem is a bum neutral safety switch. Half the time, all the neutral safety switch needs is a simple adjustment.

The neutral safety switch, which is mounted on the side of C4 and C6 transmissions and at the shifter with FMX models, is there to do two things—prevent you from starting your Mustang while it is in gear and activating the back-up lights while in reverse. Mustangs without back-up lights won't have the back-up light provision and plug. Neutral safety/back-up light switches are basically the same on C4 and C6 from '65 to '73 with the exception being harness length and plug design. The FMX's neutral safety switch is simple with adjustment instructions located on the switch itself.

A complete line of neutral safety switches are available from Virginia Classic Mustang. Mustangs Etc. has both reproduction and new-old-stock Ford neutral safety switches.

Switch Identification

Original Ford Part Number (7A247 Base) Transmission Type Specifics Location Description Revised Part Number (7A247 Base)
C4AZ-C C4 '65-'67 Before 12/15/66 Transmission Two Duplex Plugs
C7ZZ-B C4 '67 from 12/15/66 Transmission One Quad Plug C9ZZ-B
C7ZZ-C C4 '68-'69 Transmission One Quad Plug C9ZZ-B
D0ZZ-A C4 '70-'73 Transmission One Quad Plug with taller standoffs to clear locking column lever. D1FZ-A E0DZ-A
C6AZ-A C6 '67 before 12/15/66 Transmission Two Duplex Plugs
C7ZZ-A C6 '67 from 12/15/66 Transmission One Quad Plug C9ZZ-B
C7ZZ-D C6 '68-'69 Transmission One Quad Plug C9ZZ-B
D0ZZ-B C6 '70-'72 before 12/1/71 Transmission One Quad Plug with taller standoffs to clear locking column lever.
D2ZZ-C C6 '72-'73 from 12/1/71 Transmission One Quad Plug with taller standoffs to clear locking column lever. Additional plug for seatbelt interlock.
C9ZZ-A FMX '69-'72 before 12/1/71 Shifter One Quad Plug with single pin plug. C9ZZ-C D2ZZ-B
D2ZZ-A FMX '72 from 12/1/71 to 1/5/72 Shifter One Quad Plug with additional duplex plug and single pin plug. D2ZZ-B
D2ZZ-B FMX '72-'73 from 1/5/72 Shifter One Quad Plug with duplex plug and single pin plug.

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13. If you don’t have an ohmmeter or don’t know how to work one, Ford offers an alignment hole for proper adjustment. With the transmission manual lever in neutral, insert a #43 drill bit in this hole and slowly move the switch. When the drill bit sinks into the hole, you’ve achieved proper adjustment. Tighten the bolts with the drill bit in the hole. Check for proper operation in all gears. Engine should not start in R, D, or forward drive ranges. It should start only in Park and Neutral, and back-up lights should illuminate in reverse.