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Neutral Safety Switch

193rdsow

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hey guys,

I am working on a 69 RR Console Automatic and the car will only start in neutral. I am wondering if my wiring is dorked up. 3 wires to the switch- violet, black and brown. Violet is hot all the time regardless of drive selection or key position. Brown and black are unpowered regardless of key position or drive selection. Is this correct or is something miswired?

Thanks ahead of time for your help!
 
Here's a schematic

right about the middle is the neutral safety switch
sorry I couldn't blow it up much more
maybe someone more savvy could

Mopar 69 B-Body Wire Diagram 1969 Belvedere GTX Satellite RoadRunner Schmetic B.jpg
 
Middle wire (Brown) is the ground to the starter relay. Other two wires (outside two on connector) are for backup lights.

edit: The brown ground wire will only be grounded when in "Park" & "Neutral". This ground comes from inside the transmission. All other gear positions it is floating.
 
Your switch is not being depressed by the rooster tail inside the transmission at the shifter. This is usually a result of misadjustment or worn linkage, worn rooster cam or the neutral safety switch is not screwed in far enough.
 
Your switch is not being depressed by the rooster tail inside the transmission in PARK. This is usually a result of misadjustment or worn linkage, worn rooster cam or the neutral safety switch is not screwed in far enough.
 
Thanks everyone. Is it safe to say that the wiring running down to the switch is correct? Power comes down through the violet wire only and it supplies power to the switch?
 
Thanks everyone. Is it safe to say that the wiring running down to the switch is correct? Power comes down through the violet wire only and it supplies power to the switch?

The violet power wire (always hot) is only for power to the backup lights when you have the gear selector in "Reverse". It then routes that power (+12V) through the Black wire and all the way back to the backup lights, which have their own ground to chassis at the rear of the car. This then turns on the backup lights.

The violet power wire does not have anything to do with the Brown wire going to the NSS. The ground is supplied internally from the rooster comb inside the transmission when the gear selector is in "Park" or "Neutral" only. This ground then enables the coil of the starter relay when you turn the key to start. The key in the start position sends +12v on the Yellow wire to the starter relay. With BOTH ground and +12V present at the coil of the starter relay, the relay contacts close, sending high current from the battery to the starter to crank the engine over.
 
Last edited:
The violet power wire (always hot) is only for power to the backup lights when you have the gear selector in "Reverse". It then routes that power (+12V) through the Black wire and all the way back to the backup lights, which have their own ground to chassis at the rear of the car. This then turns on the backup lights.

The violet power wire does not have anything to do with the Brown wire going to the NSS. The ground is supplied internally from the rooster comb inside the transmission when the gear selector is in "Park" or "Neutral" only. This ground then enables the coil of the starter relay when you turn the key to start. The key in the start position sends +12v on the Yellow wire to the starter relay. With BOTH ground and +12V present at the coil of the starter relay, the relay contacts close, sending high current to the starter to crank the engine over.
That is what I needed. Thanks for the info!
 
does the parking pawl engage in park? If the shifter is not set up right the car will not start in park.
 
Park on an incline, move the shifter to P. If it rolls, the pawl is not locking the driveshaft and your shift linkage is off. Even if it engages, the gear selector may still not by in the right position to ground the NSS. The console shift linkage is much more straightforward than the column setup, but it can still fail. Disconnect the linkage at the shift lever on the 727 and move the lever through all the positions. It should go solidly into park. Try to start the car with e-brake engaged, should start with the lever in the park position. Check the linkage and bushings for wear.

Reconnect and have someone shift from the driver seat while you watch it, engine off so you can check for smooth movement of the linkage. If it doesnt start with linkage removed and in park, then something is wrong with your NSS or wiring to it. I've had headers burn through the NSS wiring so check for continuity. Other than that there is not much else than can cause this. However the fact that your car starts in neutral tells me that the NSS and wiring is fine, probably gear selector.
 
Park on an incline, move the shifter to P. If it rolls, the pawl is not locking the driveshaft and your shift linkage is off. Even if it engages, the gear selector may still not by in the right position to ground the NSS. The console shift linkage is much more straightforward than the column setup, but it can still fail. Disconnect the linkage at the shift lever on the 727 and move the lever through all the positions. It should go solidly into park. Try to start the car with e-brake engaged, should start with the lever in the park position. Check the linkage and bushings for wear.

Reconnect and have someone shift from the driver seat while you watch it, engine off so you can check for smooth movement of the linkage. If it doesnt start with linkage removed and in park, then something is wrong with your NSS or wiring to it. I've had headers burn through the NSS wiring so check for continuity. Other than that there is not much else than can cause this. However the fact that your car starts in neutral tells me that the NSS and wiring is fine, probably gear selector.

Good advice! Last night I fixed bad splices for the plug by soldering the wires. Thought that perhaps the problem was solved but it still only starts in neutral. I'm going to loo closer at the switch today. The rooster tail is in place and appears to be moving the switch properly. Whether it's moving in and out far enough is the next step to check. From there I will look at the linkage and will try the test you recommended. Thanks again! Very frustrating issue to track down. The back up lights aren't working either so I'm leaning towards a switch issue. More to follow
 
Ok guys. Here's the follow up. Might have this figured out. I have the NSS screwed in as tight as I can. Wiring is right. If I put the trans in reverse no lights. If I use a thin pick to depress the plastic on the switch a little bit more, lights come on. If I leave the pick wedged and slide lever to park car starts in park. I'm thinking the valve body manual lever is worn out. Anybody agree or have different ideas?
 
Ok guys. Here's the follow up. Might have this figured out. I have the NSS screwed in as tight as I can. Wiring is right. If I put the trans in reverse no lights. If I use a thin pick to depress the plastic on the switch a little bit more, lights come on. If I leave the pick wedged and slide lever to park car starts in park. I'm thinking the valve body manual lever is worn out. Anybody agree or have different ideas?

Weird as this sounds, try another switch, even a used one. The throw on the switch you currently have may be "just" instead of "positive" for both positions.
 
Having pretty similiar problem.

1-prong NSS on my 727, column shifter. Car is freshly fully restored. All bushings in the linkage new.

Linkage adjusted per FSM. Car starts first time in Park with no issue, after a ride it won't start in Park only in Neutral.

I removed the NSS and tried the old one. Even tested it with a test light (like in the manual). Continuity light came on in Neutral. In Park only when I move the gear selector on the column quicker to "P" position.

After this I readjusted the linkage another time per specs. Continuity light now stays on in Park (even if I move the selector slowly and gentle).

As soon as I drive the car it won't start again in Park when **** down.

I think the movement of the trans/drivetrain in relation to the body is what always sets off the adjustment.

What can I do? It is annoying!
 
Before you go tearing the pan down. Make sure that you have the right NSS. There are a few variants in aftermarket and some are a few threads shorter some are longer. If I find the pic of them I will post it. Even though it's a 3 pin there are variants.

Here is a pic I found real quick... Original on left aftermarket on right.
1695345181086.png
 
Before you go tearing the pan down. Make sure that you have the right NSS. There are a few variants in aftermarket and some are a few threads shorter some are longer. If I find the pic of them I will post it. Even though it's a 3 pin there are variants.

Here is a pic I found real quick... Original on left aftermarket on right.
View attachment 1528476
Both switches I have are original Mopar!
 
Both switches I have are original Mopar!
Then you may have an issue with the rooster comb on the valve body that sweeps past the switch or have the wrong switch for that year rooster comb. There are 2 different combs for a single wire NSS. I will find/post a pic I saw from another member. Hope that helps.

1695392039897.png
 
Then you may have an issue with the rooster comb on the valve body that sweeps past the switch or have the wrong switch for that year rooster comb. There are 2 different combs for a single wire NSS. I will find/post a pic I saw from another member. Hope that helps.

View attachment 1528619
I have the middle rooster and switch!

It is always working when I re-adjust the linkage. Today went for a ride, first start in P no problem. Starting again after a few accelerations, starts only in N again
 
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