73 Tach Differences - 3 or 4 wire?

[EScanlon]

I posted a Want ad for a friend of mine who is currently working on his car.

My friend's car is a 73, but he insists that his tach is a 3-wire. Which seems to run contrary to what one would think. All of the wiring schematics I have show a 4-wire. I can't find anything that would help settle the question and I haven't had a chance to look at my friends harness or tach.

One of the comments on the ad reads:

I suspect what has happened is that the car was fitted with a 260/280 tach at some point. My 73 had a 4 wire loop tach as all 240's do. Looking at the FSM for 72 and 73, the wiring diagrams all show the loop style wiring. It was not until the Fuel Injection started (late 260 and all 280) that they switched to the 3 wire negative coil side trigger tachs. ...snip...

Which upholds my (and other people's) thinking.

So, the general question to the rest of you is which tach is correct? Hopefully we can get a consensus so my friend knows what to get. He's looking for a replacement because his original tach was always intermittent, even for the prior owner.

TIA

E

[240dkw]

E: here is a photo of the tach from a 73 it looks like the 4 wire type.

Dan

[Arne]

E, I was pretty certain that the three-wire started before the end of the 240Z run. While the Nissan parts list is not helpful on this, I note that the MSA catalog lists the same tach for '70-72, and the '73 unit is different. So I'm thinking that 3-wire for a '73 might be correct.

Or at least we can assume that the '73 unit is unique in some way, if not in the 3/4 wire part.

[ChrisZ]

I can confirm that i have a late -73 240Z with a 3 wire tach, i believe you can adapt a 260Z tach to fit, but face will be slightly different.

What's wrong with the tach?

Chris

[geezer]

I have one here that was in with a parts lot I bought years ago. It looks to be the same as the one in Dan's pic. There are 4 wires pinned in the connector, but the two white wires are actually 1 wire that makes a loop and runs back to the connector. Other than that I know nothing about the reason for that. I took 1 pic and the camera died on me.

[beandip]

E: here is a photo of the tach from a 73 it looks like the 4 wire type.

Dan

Enrique, this is the same tach that I have that I told you of,

yellow/red and black wires and a all white that makes a loop.

It has the same square connector with four pins.

[beandip]

I have one here that was in with a parts lot I bought years ago. It looks to be the same as the one in Dan's pic. There are 4 wires pinned in the connector, but the two white wires are actually 1 wire that makes a loop and runs back to the connector. Other than that I know nothing about the reason for that. I took 1 pic and the camera died on me.

Ron yours is the same as mine. the loop part should be held in place by the insulated block held down with a nut. A friend of mine needed a 280 tach and I had one so we traded.

This is now my spare for my '73

[ChrisZ]

This is the back of my -73 3 wire tach.

Chris

[beandip]

This is the back of my -73 3 wire tach.

Chris

yours is different

[ChrisZ]

She keeps saying that over and over again

[tlorber]

I have a late '73 (build date 8/73 I believe) with a 3 wire. The tach is in the shop as I write this, and if they can repair it, I'll let you know what the fix was.

[dcaverre]

This is the back of my -73 3 wire tach.

Chris

That's the one!!! I am the one that Enrique has been asking for. I just became a member. My name is Dave. Thanks for the picture. Does anyone know where to find one like this? Please let me know by posting or sending me a PM. Dave