Inside the Neutral Safety Switch (or Transmission Range Switch)
Hello All,
In my quest to keep the kid’s 94 900NG running I found myself elbow deep in the engine bay pulling out the Neutral Safety Switch (NSS). We have been having problems with it and I thought it was time to take a stab at it. I had read here that others were installing bypass switches and the like and I was prepared to do the same but I thought first I’d take a look at fixing the darn thing. The one thing I new for sure was that I wasn’t going to pay the $300+ for a new one.
The problems started with the usual not being able to start the engine in PARK. We would have to put the shift leaver into neutral to get the starter to turn. Eventually that procedure no longer worked and we had to modify the starting procedure to the following: First put shift lever in Neutral; then turn the key to start and hold it there; And Finally jiggle the shift leaver in Neutral until starter engaged. WOW!
Today I pull the darn thing out and carefully disassembled it. What I found inside was interesting. The good news is that these switches are easily repairable!
To remove the switch you have to:
Remove Battery and battery tray.
Remove Auto trans fill tube (clean dirt and grime away from base of tube first so grit and grime do not fall into tube hole in transmission housing)
Unbolt various hose clamps and push hoses aside to make room for fat hands to get into switch area location
Remove nut that hold shift selector cable plate onto the NSS and lift cable plate off NSS.
Remove large nut below shift plate along with retainer washer and rubber washer (retainer washer has bend up tabs to lock large nut in place – I think this nut is only snugged when reinstalling and then washer tab is bent up to hold it –that’s what I did anyway).
Remove right and left fasteners that hold the switch in place and pry switch up off transmission shaft – It doesn’t take much force but there is a “snap in place” feature that must be overcome.
Finally unplug the two electrical connectors and cut any tie straps to get wires free. Study the connectors to make sure you understand how they come apart since there are locking features. We don’t want to break those features off now do we?
At his point the switch should be in your greasy, grimy, grubby hands! :cheesy:
The switch is fairly easy to take apart. There are 5-6 Phillips head screws on the under side that need to come out. I had to use a vice grips on one of them but they all came out.
Next take a file and pliers to the two sheet metal tabs that are swedged to hold the wire shield in place. While it looks like two of the screws hold on the lower half of the shield leave this piece in place. You have to get the other half off to split the switch housing open.
Once opened, you’ll notice the rotational contacts inside. There is a rotational arm inside with 3 spring loaded contacts. These contacts slide (or wipe) along the other switch housing half which has copper rails potted into it. The wipers conduct across a pair of bars closing the circuit.
Please see photos.
What I notice in my switch was that the contact grease had become hard and tack. The last contact, furthest from the pivot point, was actually stuck down into the leaver arm and did not appear to be making contact. This last contact looks to be the one which tells ECU what shift leaver position is in.
I cleaned every thing up. Lightly sanded the copper rails (600 grit). Reinstalled springs and contacts into leaver arm (note that 2 of the springs are connected- you’ll see what I mean). Greased everything with a generous amount of bulb grease and put her all back in place and …… Walla,... starter cranks in “Park” every time.
It was not that difficult to do and should be able to be accomplished in a Saturday afternoon.
I hope this helps!
Brian
94 900ng
2003 93 conv
1973 Jensen Healey
1997 F250 Power Stroke Diesel Crew Cab
2001 T&C Mini Van (for Sale)
1974 TVR (Project car - just sold but still parked in my garage)
Hello All,
In my quest to keep the kid’s 94 900NG running I found myself elbow deep in the engine bay pulling out the Neutral Safety Switch (NSS). We have been having problems with it and I thought it was time to take a stab at it. I had read here that others were installing bypass switches and the like and I was prepared to do the same but I thought first I’d take a look at fixing the darn thing. The one thing I new for sure was that I wasn’t going to pay the $300+ for a new one.
The problems started with the usual not being able to start the engine in PARK. We would have to put the shift leaver into neutral to get the starter to turn. Eventually that procedure no longer worked and we had to modify the starting procedure to the following: First put shift lever in Neutral; then turn the key to start and hold it there; And Finally jiggle the shift leaver in Neutral until starter engaged. WOW!
Today I pull the darn thing out and carefully disassembled it. What I found inside was interesting. The good news is that these switches are easily repairable!
To remove the switch you have to:
Remove Battery and battery tray.
Remove Auto trans fill tube (clean dirt and grime away from base of tube first so grit and grime do not fall into tube hole in transmission housing)
Unbolt various hose clamps and push hoses aside to make room for fat hands to get into switch area location
Remove nut that hold shift selector cable plate onto the NSS and lift cable plate off NSS.
Remove large nut below shift plate along with retainer washer and rubber washer (retainer washer has bend up tabs to lock large nut in place – I think this nut is only snugged when reinstalling and then washer tab is bent up to hold it –that’s what I did anyway).
Remove right and left fasteners that hold the switch in place and pry switch up off transmission shaft – It doesn’t take much force but there is a “snap in place” feature that must be overcome.
Finally unplug the two electrical connectors and cut any tie straps to get wires free. Study the connectors to make sure you understand how they come apart since there are locking features. We don’t want to break those features off now do we?
At his point the switch should be in your greasy, grimy, grubby hands! :cheesy:
The switch is fairly easy to take apart. There are 5-6 Phillips head screws on the under side that need to come out. I had to use a vice grips on one of them but they all came out.
Next take a file and pliers to the two sheet metal tabs that are swedged to hold the wire shield in place. While it looks like two of the screws hold on the lower half of the shield leave this piece in place. You have to get the other half off to split the switch housing open.
Once opened, you’ll notice the rotational contacts inside. There is a rotational arm inside with 3 spring loaded contacts. These contacts slide (or wipe) along the other switch housing half which has copper rails potted into it. The wipers conduct across a pair of bars closing the circuit.
Please see photos.
What I notice in my switch was that the contact grease had become hard and tack. The last contact, furthest from the pivot point, was actually stuck down into the leaver arm and did not appear to be making contact. This last contact looks to be the one which tells ECU what shift leaver position is in.
I cleaned every thing up. Lightly sanded the copper rails (600 grit). Reinstalled springs and contacts into leaver arm (note that 2 of the springs are connected- you’ll see what I mean). Greased everything with a generous amount of bulb grease and put her all back in place and …… Walla,... starter cranks in “Park” every time.
It was not that difficult to do and should be able to be accomplished in a Saturday afternoon.
I hope this helps!
Brian
94 900ng
2003 93 conv
1973 Jensen Healey
1997 F250 Power Stroke Diesel Crew Cab
2001 T&C Mini Van (for Sale)
1974 TVR (Project car - just sold but still parked in my garage)