I "think" my 4-speed has a neutral switch in it, up near the top plate, by the shifter. I "think" it's a neutral switch because it's there in the right spot for one, but not actually working. It does not change state in gear or neutral. It's open all the time.

So:

1) The switch is probably bad.

2) Was it used to inhibit the start circuit unless in neutral?

3) What years was it used in the 4 speeds?

4) My 72 car is wired with a 72 automatic harness, should I tie the neutral switch wires from the harness to this switch, when I fix it, if i want the inhibit to function?

Thanks!

PS: I just ordered a 72 wiring diagram from ebay because the FSM one is :stupid:

Edited February 23, 201015 yr by cygnusx1

I think that's the switch for the backup lights. Put it in reverse and see if it closes. The auto harness has a lead to a switch that keeps the trans from down shifting into first when it is cold and a neutral switch.

The reverse switch is near the filler plug up front passengers side, I found that one. This switch is up near the shifter, passengers side. It's out of reach of any factory harness wires. Then again my harness is for an auto so I am not surprised.

Edited February 23, 201015 yr by cygnusx1

It isn't a neutral switch. The later 280Z had a high gear switch that ran to the distributor to increase the spark advance at highway speeds. At least that is what I read somewhere on this site.

(I can't find the other thread now...)

The 4 speed that was in my 240Z when I bought it also had that same switch up at the top of the housing near the shifter. It is useless on any car except the 280Z. It seems like someone said even those cars ran better with the switch disconnected.

I have a 280Z which had a top gear switch originally. The switch turned on the vacuum advance in top gear (4th) for better economy and reduced emissions.

This trans is an early 4 speed (probably 72) and the FSM points to the switch as a neutral safety switch. However, none of the wires of my harness (from an automatic car) can reach it.

If in fact Nissan included a neutral safety switch in the early manual trans, there must be some early Z's out there that will not start when the shifter is in gear. No?

Edited February 24, 201015 yr by cygnusx1

I searched the various FSMs until I found references to a neutral switch on a manual transmission. There is no switch shown on the 71 FSM, which is why I didn't think the transmission had such a thing. The earliest reference that I could find was in the 73 manual, so I assume that is the year transmission you have.

If you want to hook this switch up I would just make up some extension wires to get it to the neutral interlock connection in your automatic wiring harness. The switch may just be out of adjustment. On the other hand I suspect that most people just jumper the two interlock wires from the automatic harness and live without the neutral interlock. You would just have to remember not to start the car without pressing the clutch pedal down.

I personally don't think I ever owned a car with a manual transmission that wouldn't start in gear.

Just one of those things you have to get used to doing.

Great! Then I need to ID which two harness wires will need to short out, to eliminate the neutral switch.

I have never owned an automatic so I have some questions for those that do:

In a 72 automatic Z car..what gadgets were in place to prevent the car from starting? I will need to bypass these gadgets when it comes time to fire the baby up. I want to find them NOW while the car is on stands and in parts.

Neutral Switch?

Seat switch?

Seat belt switches?

Retina Scanner? (just kidding)

??? any more

Walter, I agree! I have driven stick all my life, and I am 42 now. I can't physically turn the ignition key unless I wiggle the shifter first ;-) Who needs interlocks!

Wish you had a pic of the safety switch on the manual trans, never seen that yet.

The 260Z had a neutral switch in the manual transmission to go with the horrid interlock relay system in the car. I don't have a picture of the switch, though.

The switch is IDENTICAL to the reverse switch. Napa lists the two with the same part number, but AutoZone lists them separately. $11 at Autozone for the Neutral and $24 for the reverse(NLA).

So just go to Autozone and buy a neutral safety switch if you need a reverse switch. It's cheaper AND available for $11 ;-)

The neutral switch screws into the upper tail of the trans on the passengers side. My 76 280Z 4-speed had a blank boss but no sensor. My current four speed has the sensor. It must be either a 73 or 74 trans??

Edited February 25, 201015 yr by cygnusx1

Steve what does the interlock system in the 260Z entail?

Steve what does the interlock system in the 260Z entail?

It entails a lot of frustration.

Here is a picture from the FSM (along with my suggestion on how to jumper it out once it's disconnected). The neutral switch completes a circuit to the ignition interlock unit if the transmission is in neutral, a seat is occupied without the seatbelt in use, and the key is in the run position. This will light the seatbelt warning light and sound the buzzer. (Note: the drawing shows a normally open switch, and that's how I described the operation. However, it doesn't make sense to me. I would think it should be a normally closed switch, so if the car is in gear, the buzzer & light would be present.)

The interlock was the idea of the brilliant bureaucrats in the federal government. (Disclaimer: At one time I was a bureaucrat, but I was disgusted by the thought of wasting the taxpayers' money, so I got a real job.) If someone set a bag of groceries down in the passenger seat, the car would not start unless the bag was securely buckled in. Of course, I do not advocate utilizing the passenger seat (or driver seat) for grocery storage during transit, but the system just didn't work that well. Many people just left their seatbelts buckled all of the time to reduce the headaches.