: 1964 Sedan DeVille - Neutral Safety Switch Problem

01-31-13, 07:38 PM
Hi all, I am new to this site after recently importing a 1964 Sedan DeVille to Australia.

Anyway, I am having some issues with the neutral safety switch (NSS) in my 64 Deville. My car starts in all gears, and upon closer inspection it appears that the wires that connect to the outer connectors (part 1993653) have been bypassed – hence it starts in gear.

I have played around with the switch and even replaced it with a used switch (managed to track down one here in Australia). Same problem, it keeps starting in gear, so I am not sure if it is a faulty switch or what!

Here is where it gets interesting…. The car has a 390 rather than the 427. The transmission as far as I know is a Turbo (Shifter sequence - PRNDL).

My dilemma is that I can buy a part from the States, ($550 + shipping) however I am not sure if this is the underlying issue. I have already spent $250 on a NSS from Australia and I am hesitant to spend more money on a new NSS as I am not sure if this is the actual problem!

Does anyway have any thoughts on what the issue may be, experiences a similar issue or have any advice as I am completely stuck!

Thanks for your assistance!

02-01-13, 02:15 PM
Welcome to this forum, Paulmac :)

The problem of the car starting on any gear should come from this switch. That´s the part that should prevent this to happen. I think there is a procedure to install a new one -at least that´s what I read on my '69 cadillac manual-. Did you follow the manual procedure? ¿Are your back-up lights working in reverse? They should be controlled by this switch, as well as the automatic parking brake release.

You don´t have to pay so much for this part. Check Ebay.com You have 5 items from $ 100 + shipping: http://www.ebay.com/sch/i.html?_trksid=p5197.m570.l1313&_nkw=64+cadillac+neutral+safety&_sacat=0&_from=R40

02-04-13, 09:30 PM
103398I am still no closer to working out the issue with the NSS. I have downloaded a wiring diagram and will try to go over all the wires over the weekend to make sure there isnt a loose connection somewhere along the line.
I have been researching and researching and come up with this idea.... The motor is a 390. I assume this would be out of a 63??
The trans seems to be the TH400 (due to the shift sequence). The current NSS is for the TH400 / TILT 1964 model. Would it be possible that the motor was replaced (as I said, its got a 390 not the 427) and the NSS bypassed as it was no longer compatitble - as the motor was not the 427?
The part that is currently in the car and not working is NSS 1993653. Would it be worth testing a new NSS from a 1963 Deville (with Tilt) or would this be useless as the TH400 didnt appear until 1964?
The park brake releases and I will have to check the back up lights.

02-05-13, 07:17 AM
Your model seems a '64. Anyway, I don´t think that changing the engine may cause the problem. It has to do with the ignition wiring diagram. The connections have to be plugged to the right wire at every side of the NSS and the switch has to be in the correct position (not turned to one or other side), so the starter only receives power in "P" or "N". Maybe in the past, the switch failed so the previous owner bypassed the system. If you did not correct this bypass, the switch is working ok but the car starts in any gear due to this.

Thanks por the pic. It looks a beautiful clean unit :thumbsup:

04-10-13, 07:45 PM
An update on the NSS - I finally worked it out!!! I managed to pull the NSS out, it was putrid and broken. The plastic fork had a crack in it so it wasn't operating as it should, hence the previous owner bypassed the switch all together. I researched the NSS used for the 64 and sure enough it was the year the T400 was introduced, and 4 seperate switches were available. the non-tilt/Hydra; Non-tilt/turbo; Tilt/Hydra; tilt/turbo. Mine is the tilt turbo, which happens to be one of the hardest NSS's to find!
I ended up getting a NSS # 688 (from the 65 i think) and with a slight mod it works. Cost $110 from the USA delivered to Australia so now my car only starts in P & N, the reversing lights work and the auto parking brake works! Super happy!
Now to fix the clock......106589

01-27-14, 10:50 PM

I have recently purchased a '64 De Ville with a 429/TH400 and am unaware of the "auto parking brake" that you refer to. Can you enlighten me on this feature please? I have been a Corvette owner for 20+ years and am new to Caddys, so anything you can help me with would be much appreciated.

Regards from Down Under.


01-27-14, 11:18 PM
Aussie, i think he is referring to the automatic parking brake release offered in Cadillacs. You can tell if yours has one by looking behind the parking brake under the dash. If there is a vacuum actuator there it is equipped. It is triggered by a switch in the steering column so when you put the car in gear it will send vacuum there and release the brake if it is applied.

01-28-14, 01:41 AM
And you will have better luck starting a new thread! This thread is almost a year old.

01-30-14, 08:36 AM
As far as engines go, the '64 is a bit of an enigma. The 429 engine was new for 64 but there were still quite a few 390s left over from 63 production, so many pre-january production 64s have 1963 390 engines rather than the then new 429.

01-30-14, 10:00 AM
As far as engines go, the '64 is a bit of an enigma. The 429 engine was new for 64 but there were still quite a few 390s left over from 63 production, so many pre-january production 64s have 1963 390 engines rather than the then new 429.

I have heard these remaining engines from past years (at least many of them) equipped cars shipped to overseas (most of them to South America or Mexico).

02-02-14, 06:15 PM

Thank you for the explanation, I had never heard of this before. I have owned Corvettes for a few decades and thought that [I][B]they[B][I] were the epitome of the GM fleet, but obviously I still have a lot to learn. But it will be a fun learning process thanks to the input of knowledgeable people like you.

Regards from Down Under.


02-10-14, 11:31 PM
Hi Aussie John, yes the auto park brake release runs off a vacuum. Once the shifter is moved out of park the park brake automatically releases.
My NSS was completely bypassed when I bought it... I ended up using a reconditioned switch from a 65 with some mods.
Out of curiosity, how do you release your parking brake?

02-11-14, 01:20 AM

I don't know, as the car is still in California having some work done on it to make it roadworthy by a recognised Cadillac expert there. Such people are thin on the ground over here, however, I will ask him and let you know what he says. We'll have to catch up if I ever decide to take the car to Sydney.

Regards from Down Under.