reverse lights can be irritating

[VA-AMCjeep]

I'm a longtime member of ifsja but it seems like it's a lot slower than it used to be....

I have an 84 j10 with the 727 trans and my reverse lights are being jerks. I've tested the harness at various connectors and I can put 12v on the reverse light wire (in my case it's a white wire with trace) and when jumped the reverse lights come on, also I can connect the 12v wire on the NSS connector to the reverse wire on the neutral safety switch connector and the lights work, so I unless I'm missing something the wiring is ok. I've studied the wiring diagrams and everything is correct.

So that leaves me with the neutral safety switch itself. I connected a new NSS to the connector and when I press down the plunger of the switch the lights work, so does that mean something in the trans is messed up? The jeep starts only in park and drive which is correct, it's just these darn lights. If I knew of a way to connect a stand alone reverse light switch it would be good...

[Phils67]

There are 2 switches, one is NSS and the other is for reverse lights, am i correct? So what would the NSS have to do with the lights? If your reverse switch is the ball style I have seen where certain aftermarket switches do not depress far enough while installed. I would recommend using an OEM switch before condemning the transmission. Maybe i am missing something here?

[tgreese]

If you are having trouble with the '84 diagram, take a look at any of the other diagrams in comparable years. The TF727 started in 1980, so I looked at the 1980 diagram, and it appears that the NSS does indeed control the backup lights. There is a connector that goes to the NSS, backup, and 4WD indicator. That could be two switches, one on the transmission shifter and one on the transfer case.

On the 1980 diagram, the backup lights are white with a trace line, going through the bulkhead as connection 34, but they go nowhere. They then connect to a frame harness, still w/tr and continuing to the rear for the lights. It appears that the backup and NSS are the same switch. There should be one wire (red) that has power all the time when the key is on, then it connects to the lamps when the shifter is in reverse. The NSS works differently - the ground on the starter solenoid is isolated (connection on the bottom of the solenoid), and is connected to ground only when the shifter is in park or neutral. So there is no reason for the switch to have power except to light the backup lamps.

So you have a new switch and it still does not light with the shifter in reverse? And you can light the lamps by turning the switch manually? That suggests that the alignment of the switch is off wrt the rotation of the shift arm. You'll have to look where the switch is mounted and see how both functions are activated. Sounds like the electrical part of the equation is complete.

Bypassing is easy. Run the red power wire to a switch, then back to the white wire that goes to the backup lamps. You could pick up power from the main splice under the dash, and connect to 34 on the bulkhead. I suspect you will be unhappy with this arrangement though.

[VA-AMCjeep]

There are 2 switches, one is NSS and the other is for reverse lights, am i correct? So what would the NSS have to do with the lights? If your reverse switch is the ball style I have seen where certain aftermarket switches do not depress far enough while installed. I would recommend using an OEM switch before condemning the transmission. Maybe i am missing something here?

The 727 trans has an all in one neutral safety switch that controls 4wd indicator, reverse lights, and neutral/park starting. 4wd light and park/neutral starting work.

[VA-AMCjeep]

If you are having trouble with the '84 diagram, take a look at any of the other diagrams in comparable years. The TF727 started in 1980, so I looked at the 1980 diagram, and it appears that the NSS does indeed control the backup lights. There is a connector that goes to the NSS, backup, and 4WD indicator. That could be two switches, one on the transmission shifter and one on the transfer case. .

On the 1980 diagram, the backup lights are white with a trace line, going through the bulkhead as connection 34, but they go nowhere. They then connect to a frame harness, still w/tr and continuing to the rear for the lights. It appears that the backup and NSS are the same switch. There should be one wire (red) that has power all the time when the key is on, then it connects to the lamps when the shifter is in reverse. The NSS works differently - the ground on the starter solenoid is isolated (connection on the bottom of the solenoid), and is connected to ground only when the shifter is in park or neutral. So there is no reason for the switch to have power except to light the backup lamps. .

I actually made a diagram that isolates just this circuit and the white trace wire 34 goes from the reverse lights to the frame harness connector, then to the bulkhead and into the BU fuse in the fuse block, after that they go to a connector back behind the engine and then to the NSS connector. The 4wd light works and the park/neutral starting works, that's the part that I don't understand. is there something in the trans that can wear out just the reverse lights?

So you have a new switch and it still does not light with the shifter in reverse? And you can light the lamps by turning the switch manually? That suggests that the alignment of the switch is off wrt the rotation of the shift arm. You'll have to look where the switch is mounted and see how both functions are activated. Sounds like the electrical part of the equation is complete.

Correct, the switch screws into the transmission

Bypassing is easy. Run the red power wire to a switch, then back to the white wire that goes to the backup lamps. You could pick up power from the main splice under the dash, and connect to 34 on the bulkhead. I suspect you will be unhappy with this arrangement though.

I was thinking more of an intermittent switch like what is used in aftermarket shifters, but the stock column and shift mechanism makes that hard to do.

[Phils67]

I was questioning myself while replying. Im not very familiar with the automatic trans

[VA-AMCjeep]

I was questioning myself while replying. Im not very familiar with the automatic trans

No problems I question myself all the time with this jeep...

[Phils67]

Haha exactly. Its Jeep thing, thats why we don't understand. I have spent weeks on end scratching my head with these damn things in the past

[brandtjohnd]

I had a similar issue where reverse lights were not working. They are now!

I removed the Neutral safety switch(NSS) from the transmission and tested it, while hooked up to the wiring harness. To my surprise the reverse lights came on. So when the NSS button is fully extended the reverse lights work. When you push the button/plunger in, the lights go off. At this point i was able to determine that my bulb, wiring, NSS & 12v Power were working correctly. What was not working was the mechanism inside the transmission that actually moved the NSS button/plunger.

Dropped the Tranny pan and saw what is called the rooster comb. It interacts with the NSS and pushes or releases the NSS button/plunger depending on where your gear selector is placed (PRND12). I discovered that when when the NSS is installed and the gear selector was in Reverse, the mechanism didn't let the button/plunger extend enough to connect the circuit and power the reverse lights. It was off by no more than a 16th of an inch. Since there is a plastic piece that actually does the pushing of the button, i ground it down enough to let the switch work properly.

Now my reverse lights work. I suppose I could have used a new/thicker rubber gasket on the outside of the NSS when installing it to gain the clearance also, but you live and learn.

Best of luck. Its a simple system. Keep at it.

[81waggy]

I wired in a toggle switch for my reverse lights. I have a 4l60e with a floor shifter. it was easier wiring a toggle switch than getting the NSS to work correctly.

Pretty easy since you already isolated the wire for the reverse lights. Just connect it and a 12v ACC wire and your all set. I would suggest getting a toggle switch that lights up when its "on" . Nothing like driving down the highway with the reverse lights on.

[candymancan]

nss is just that.. neutral safety switch.. it controls the reverse lights as well its a safety feature added to transmission along time ago.

My reverse ligjts on my 98 zj stopped working one day and i replaced the switch on the transmission and the lights worked again