The NSS (Neutral Safety Switch) controls several things. The switch is located near the base of the steering column up around the top facing the dash. (see picture above).
Information about the switch, installation, removal and adjustment can be found in your 1963 Shop Manual on page 12-47 section 70; and in the 1964 Cadillac Shop Manual on page 12-49 section 69.
Functions it controls include:
Park Brake Release: There is a vacuum valve on top of the NSS fed by the vacuum line that comes in from the intake, that goes to the left to the NSS. When the gear shift left is moved to any of the drive ranges (taken out of Park or Neutral) it allows vacuum to go to the brake release diaphragm on the Park Brake assembly. These sometimes leak and you will usually hear air leaking as you shift thru the gears. This is one area that can introduce a vacuum leak that can affect ac/heat, engine ignition, etc. NOTE: If leaking the feed vacuum line can be unplugged from NSS and plugged at the end to eliminate the leak. This means the Automatic Release on the Park Brake will not work and you will have to always release the brake with the hand lever. NOTE 2: You cannot simply bypass the NSS and attached the vacuum line directly to the Park Brake as it will always have vacuum on the diaphragm actuator and will be constantly trying to release the brake (i.e. Park Brake will not work).
Reverse Lights: When gear shift lever is in Reverse it closes circuit between light green wire and Pink with black stripe wire, turning backup lights on. These can be jumpered to bypass NSS and test backup lights with out neutral safety switch.
Neutral Safety Switch: The engine should start in Park and Neutral Only. When in Park or Neutral the switch closes the circuit between the violet (purple) and dark blue wire.
Neutral Safety Switch Can Be Bypassed
If Neutral Safety Switch is defective it can be bypassed by using a jumper wire across the blue and purple wire connector. Disconnect the connector with blue and purple wire and run a jumper wire across the contacts. This closes the circuit to the ignition allowing the car to crank.
WARNING: Bypassing the Neutral Safety Switch with a jumper wire means the car can then be cranked in any gear, including the drive gears!
Horn Contact: non -tilt columns also have a horn contact wire and plunger to ground the horn.
Neutral Safety Switches Used in 1963 and 1964
There were two neutral safety switches for 1963 and four for 1964.
Here is the breakdown by year:
1960 to 1963: used switch with part # 199 3560
Master Parts Book says to remove horn contact plunger when used on 1963 cars with tilt steering.
1963 with tilt: used switch with part # 199 3622
Master Parts Book says when exhausted use Part # 199 3560
1964: 4 switches used depended on tilt or non-tilt column and transmission
- Non-Tilt/Hydramatic - Part # 199 3650 (650 stamped on switch)
- Tilt/Hydramatic - Part # 199 3651 (651 stamped on switch)
- Non-Tilt/Turbo Hydramatic - Part # 199 3652 (652 stamped on switch)
- Tilt/Turbo Hydramatic - Part # 199 3653 (653 stamped on switch)
1965: 2 switches were used:
- 1965 75 Series - Part # 199 3652 (652 stamped on switch)
- 1965 All other body styles - Part # 199 3688 (688 stamped on switch)
1966: All used the 199 3688 Switch
Also: The 1965-1966 '688' NSS (part # 199 3688) will replace 653 ('64 with tilt wheel & TH trans) with minor modification:
- file the fork down a bit or shim it up with tiny flat washers.- Will Not work as a replacement for the 650 (hydramatic & non-tilt) and 651 (hydramatic & tilt) due to difference in shift pattern.
- Will Not work as a replacement for the 652 (TH & non-tilt) as the non-tilt has the horn contact button that engages the column as part of the switch.
1967-1966: all body styles: - Part # 199 3386 (386 stamped on switch)
See MPB scan below:
Example of 560 NSS:
Example of 622 NSS (Note broken slider that engages column)
Example of 652 NSS:
Comment
Dan, There are just two vacuum nipples on the NSS and it doesn't matter which hose goes on which nipple as the vacuum valve function simply shuts off the vacuum passage or opens it up. In other words think of it as a closed door or open door with the either vacuum line on either side.
Edward, the plunger is the horn contact found on non-tilt NSSs that feeds the horn circuit.
Posted a scan of 1965 Master Parts Book Neutral Safety Switch section.
Travis J. Hensley Online
Started by Jacob Foster in 1963/64 Cadillac Specific Discussion. Last reply by Jacob Foster 7 hours ago. 4 Replies 0 Likes
Hello All! I’m struggling to find an answer to this question, hoping a member can help. Can I swap the crankshaft from a 1966 429 w/TH400 to my 1964 429 w/TH400 trans? I came across an article that…Continue
Started by Jason Edge in Newsletters. Last reply by Dennis P. DiBari 11 hours ago. 1 Reply 0 Likes
I have just completed and posted the July 2025, 1963/64 Cadillac Chapter Newsletter to our…Continue
Tags: Chapter, Newsletter, Posted, Cadillac, 1964
Started by Mark Geertsma in 1963/64 Cadillac Specific Discussion. Last reply by Kenneth Barton yesterday. 4 Replies 0 Likes
Hi all,Again I have issues with my AC system. Had it refilled recently but within a few days the system was empty again. The AC mechanic added tracer fluid to check for leaks, but there are no…Continue
Tags: 1963, core, evaporator, AC
Started by Dave Fehrle in 1963/64 Cadillac Specific Discussion. Last reply by Tony Prichard yesterday. 4 Replies 0 Likes
I have finished replacing all the rear suspension and am at the last item, which is bleeding the rear brakes. I am using the Jason Edge vacuum pump method and all went well with the rear passenger…Continue
Posted by SK on June 2, 2025 at 2:20pm 2 Comments 0 Likes
Could someone post front and back photos of the 1963 right-hand kick panel with A/C?
My car didn’t come with the original kick panels, so it's a bit of a mystery to me how I should cut the backing board and carpet to fit around the A/C.
Many thanks,
-Samu
Posted by Chase on March 12, 2025 at 2:05pm 14 Comments 1 Like
Hey guys,
I have installed the same Edelbrock carb and have done everything the same as Jason’s carb and intake project. In the spring and summer months the car starts, runs and idles great! In the fall and winter months on a cold start, the car starts awful and wants to die until it warms up. I have to keep my foot on the throttle until it warms up or it will idle just terrible and try to die. Once it’s warm, it runs fantastic! Whats going on here? I was thinking of removing the…
ContinuePosted by Ray Schick on August 22, 2024 at 6:25pm 2 Comments 0 Likes
I bought this seat material thinking that it’s…
July 20, 2025 from 8pm to 9:30pm – Zoom
0 Comments 0 LikesSwitch to the Mobile Optimized View
© 2025 Created by Jason Edge.
Powered by
You need to be a member of 63/64 Cadillac Website to add comments!
Join 63/64 Cadillac Website