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3 prong 904 NSS switch?

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asifnyc View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote asifnyc Quote  Post ReplyReply Direct Link To This Post Topic: 3 prong 904 NSS switch?
    Posted: Apr/26/2018 at 6:42pm
can anyone explain to me how this switch works.  more specifically, how I can bench test one with a voltage meter?

I've put a 904 in a '71 javelin and am trying to tie the existing wiring from the floor mount NSS that was used with the M12 to the in-transmission 904 neutral saftey switch.

done a lot of research on the web and am still scratching my head. 

thanks!

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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Apr/26/2018 at 6:59pm
OK, the center is the neutral switch part and the switch GROUNDS the center contact when in N or P.
The outer two are connected together when in R (backup lights - one gets power and the other goes to the backup lights in back)

Connect an ohm meter to the outer two terminals and there should be 0 ohms, or continuity between the two outer ones when in R.

Now to use the center as neutral safety switch - the original as I recall makes or breaks the power from the key to the solenoid.
If you want it to work on your Javelin, you can use a starter solenoid (fender mount, ford type) that is for a 73 or so with Automatic transmission and it required a ground to the rear terminal to operate and you'd tie the two wires from the original NSS together. 
OR you can rig a RELAY that the MOPAR NSS would ground and connect the original wires - so you could actually wire the NSS the way Chrysler did on their cars.

if you want details on that I can lay out a diagram showing what to use and how.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote asifnyc Quote  Post ReplyReply Direct Link To This Post Posted: Apr/26/2018 at 11:29pm
thanks bill!  The car does have a fender mount solenoid (relay? same thing?) and no solenoid on the starter.  are you talking about the "I" terminal when you say "rear terminal".  the wiring harness has a plug for both "S" and "I" terminals... so there is already a wiring going to the rear terminal (if I'm following you).

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Post Options Post Options   Thanks (0) Thanks(0)   Quote 1970390amx Quote  Post ReplyReply Direct Link To This Post Posted: Apr/26/2018 at 11:38pm
This is the style of solenoid BILLD is talking about. The center pin on the rear of the solenoid must be grounded for the solenoid to work. A wire can be run from that terminal to the center pin on the neutral safety switch. It was used on a lot of amc and jeep automatic equip cars.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote asifnyc Quote  Post ReplyReply Direct Link To This Post Posted: Apr/27/2018 at 12:03am
ok thanks! the solenoid in the car right now does not have a rear pin BUT I'm pretty sure I have one with a rear pin in my parts pile.  I'll see if I can find it and swap it out.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Apr/27/2018 at 1:03pm
Yup - he's exactly right. It would SURE simplify things for you to use one of those. They look original (because AMC used those on the later automatics anyway) and it involves a single wire from the center NSS pin to the ground on the back of the solenoid.
Note - the solenoids for the stick or early AMC had a bracket that mounted the solenoid almost perfectly up and down. those with the rear connector mount at a bit of an angle to allow space for that connection on the back.

S and I terminals should remain the same.....
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Post Options Post Options   Thanks (0) Thanks(0)   Quote asifnyc Quote  Post ReplyReply Direct Link To This Post Posted: Apr/30/2018 at 11:55pm
just following up here (and thanks again for all the help)...

I did have one of those starter solenoids with the rear pin and the angled bracket.  Hooked a connector to that and ran a wire into the car.

for the NSS I had the one in the trans and a new one on the bench.  after understanding how the switch works I tested the installed NSS and it did not seem to be working. So I pulled it out and was able to see that the center contact was broken and sunk in (this is the part of the switch that is inside the trans).

So I replaced it with the new one and I have the NSS working.  I can start in P/N and not in any other gear.

BUT the brake light circuit does not work (I mean just at the switch).  In reverse the outside pins do not have continuity.  I tested this switch on the bench and the pins have continuity until you depress the switch.  I've looked at the the cam (or whatever you call it) that contacts the switch and it looks like I expect it to. meaning in reverse the cam has an open area that should allow the plunger to extend which should allow the outside pins to have continuity.  but they don't.  

any ideas? the only difference I saw between the original switch and the replacement is that the plunger on the new switch is a complete circle and the original switch had four slots/groves. the only thing I can imagine is that the plunger of the new switch is not able to full release when in reverse...



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Post Options Post Options   Thanks (0) Thanks(0)   Quote 1970390amx Quote  Post ReplyReply Direct Link To This Post Posted: May/01/2018 at 7:02pm
There is a plastic piece in the trans that keeps that center pin from grounding except in park and neutral. 
That plastic piece also has a small indentation at the reverse position, that  allows the pin to stick out like it does when the switch is out of the trans. My guess would be that it is damaged and that is why the old switch was damaged.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 74AMCJAV Quote  Post ReplyReply Direct Link To This Post Posted: Jun/19/2018 at 6:49am
Just reading this post and wondering if you could help me source out my NSS / Seatbelt interlock issue. It appears that someone removed the seatbelt interlock relay that was mounted on fender well and jumped a few wires together allowing it to start .. but it starts in any gear! The NSS switch is new .. the reverse lights work .. but starts in any gear. My question is:

Should I just get a Ford type starter solinoid with the ground in the rear and simply run a separate wire from the ground on the solinoid down to center pin on NSS??
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 6PakBee Quote  Post ReplyReply Direct Link To This Post Posted: Jun/19/2018 at 8:41am
Originally posted by 74AMCJAV 74AMCJAV wrote:

Just reading this post and wondering if you could help me source out my NSS / Seatbelt interlock issue. It appears that someone removed the seatbelt interlock relay that was mounted on fender well and jumped a few wires together allowing it to start .. but it starts in any gear! The NSS switch is new .. the reverse lights work .. but starts in any gear. My question is:

Should I just get a Ford type starter solinoid with the ground in the rear and simply run a separate wire from the ground on the solinoid down to center pin on NSS??


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