Neutral Safety Switch HOWTO - The 1947 - Present Chevrolet & GMC Truck Message Board Network

67chevytodd · 08-19-2004, 10:17 PM

I am changing my 67 from a manual to an auto TH350 I have a colum from a donor 72 C-10. My problem is with the neutral safety switch. How do I need to wire it to make it function? There are two purple wires, one dark green and one light green (4 wires total) Where do I hook them into the wiring harness. Also, on the tranny itself there is the backup light switch. Does this plug in the TH350 the same way as the manual? Thanks, Todd

Robert1970C20rstbukt · 08-19-2004, 10:31 PM

There isn't a backup light switch on Autos, just on standards. The backup switch is down on top of the column, by where it meets the firewall. As for the safety switch, I'm not really sure how it's wired. I need to find out too, mine doesn't even work. I can have the shifter in drive and it'll crank right up, not very safe. I keep the emergency brake on every time I park it.

64fleetside · 08-19-2004, 11:16 PM

Find the large purple wire coming out of the ignition switch(start). Cut & splice in the two wire connector for neutral safety switch. Use good connectors, or solder & tape or heat shrink. Adjust switch til truck cranks in Park & Neutral only. Green wires hook to green wires near column if truck was column shift, usually if hasn't been cut will hook right up to new neutral switch. *Not responsible for fires*Brian

fatfords · 08-19-2004, 11:17 PM

There should be a purple wire (I think) from the ignition switch to the bulkhead connector, behind the fuse block. The "new" purple wires on your auto column are the "neutral/safety" wires. One will hook to the "start" position (ignition switch) and the other to the bulkhead connector. This one goes to the starter solenoid (hot side) under the hood. AThe N/S switch itself will rotate around the column (down by the firewall) so that it can be adjusted to only start in the "park" and "neutral" positions.

The green wires are part of the back-up lights circuit. There is not a switch on the tranny. I don't have my wiring diagrams with me, but I will check it out tomorrow if someone else doesn't chime in.
Good Luck!

fatfords · 08-19-2004, 11:18 PM

64Fleetside can obviously type faster than me!

08-19-2004, 10:17 PM	#1
67chevytodd Junior Member Join Date: Aug 2003 Location: SW Nebraska Posts: 50	Neutral Safety Switch HOWTO I am changing my 67 from a manual to an auto TH350 I have a colum from a donor 72 C-10. My problem is with the neutral safety switch. How do I need to wire it to make it function? There are two purple wires, one dark green and one light green (4 wires total) Where do I hook them into the wiring harness. Also, on the tranny itself there is the backup light switch. Does this plug in the TH350 the same way as the manual? Thanks, Todd __________________ Old Chevys never die they are just reborn!

08-19-2004, 10:31 PM	#2
Robert1970C20rstbukt Registered User Join Date: Jun 2004 Location: Beeville, Texas Posts: 1,943	There isn't a backup light switch on Autos, just on standards. The backup switch is down on top of the column, by where it meets the firewall. As for the safety switch, I'm not really sure how it's wired. I need to find out too, mine doesn't even work. I can have the shifter in drive and it'll crank right up, not very safe. I keep the emergency brake on every time I park it. __________________ RJD 1984 Chevrolet C30 welding truck 454/SM465 1977 GMC C15 pickup 350/TH350 1970 Chevrolet C20 pickup 350/TH400 1970 Chevrolet K20 Suburban 454/TH350 1969 GMC 8500 478M V6/5 spd winch truck Last edited by Robert1970C20rstbukt; 08-19-2004 at 10:34 PM.

08-19-2004, 11:17 PM	#4
fatfords Registered User Join Date: Sep 2002 Location: DFW, TX Posts: 350	There should be a purple wire (I think) from the ignition switch to the bulkhead connector, behind the fuse block. The "new" purple wires on your auto column are the "neutral/safety" wires. One will hook to the "start" position (ignition switch) and the other to the bulkhead connector. This one goes to the starter solenoid (hot side) under the hood. AThe N/S switch itself will rotate around the column (down by the firewall) so that it can be adjusted to only start in the "park" and "neutral" positions. The green wires are part of the back-up lights circuit. There is not a switch on the tranny. I don't have my wiring diagrams with me, but I will check it out tomorrow if someone else doesn't chime in. Good Luck! __________________ '56 F-100 (w/all GM stuff) Lookin' for another parts chaser! '05 GMC crew cab

08-19-2004, 11:18 PM	#5
fatfords Registered User Join Date: Sep 2002 Location: DFW, TX Posts: 350	64Fleetside can obviously type faster than me! __________________ '56 F-100 (w/all GM stuff) Lookin' for another parts chaser! '05 GMC crew cab

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08-19-2004, 11:16 PM	#3
64fleetside Registered User Join Date: Apr 2004 Location: arkieland Posts: 1,070	Find the large purple wire coming out of the ignition switch(start). Cut & splice in the two wire connector for neutral safety switch. Use good connectors, or solder & tape or heat shrink. Adjust switch til truck cranks in Park & Neutral only. Green wires hook to green wires near column if truck was column shift, usually if hasn't been cut will hook right up to new neutral switch. Not responsible for firesBrian



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