Jump to content

A 240z and the trials of trying to reconnect the wiring harness


Recommended Posts

First a little background, I bought this in 1988 as a Scarab conversion. Later sold the 327 and other components of the conversion. Now I am installing a '83 280ZX

non-turbo with SUs. Fortunately the previous owner did not butcher the wiring harness other than cut the water temp sensor wire shorter. Over the past few years I completely disassembled the entire car and now I am in the process of rebuilding. Which get's me to my current project of reinstalling the wiring harness.



Pictured are 4 wires currently causing my current frustrations. The yellow wire is water temp, the Green/white and one of the black/white wires

go along the passenger side rail across the front and over to the area where the coil and ballast resister were located, where they originally terminated. The second black/white wire is about 35 inches long and ends near the front of the engine connected to ??? ( this wire has not been cut)


I tested continuity of the g/w and b/w wires came up with the following:

The g/w is connected to the tach and the start position of the ignition switch.

The long b/w is connected to the tach.

The short b/w is connected to the run position on the ignition switch.

According to the schematics I have looked at, the short b/w should connect to the ballast resistor along with the g/w . But since it is about 4 feet short it can't.

And to add to the confusion the long b/w should connect to the + side of the coil.


As of yet I do not have a battery or coil and I am trying to make sure all connections will be correct before I get them .


I am using the 280ZX distributer. so will not need the ballast. I have read the discussions about the changes needed to the wiring to make that work.

It would seem all I need to do is connect the long g/w wire to the short b/w wire and make the other wiring change between the coil and the IC.

But, being curious I am wondering what the short b/w was originally connected to , and how in the world the original set up worked since it seems It had no connection to coil +.


Any education will be appreciated. Thanks.

Edited by Duff
Link to comment
Share on other sites

Please excuse typos, I haven't figured out how to edit after previewing the post. 




Click on Edit at bottom of post to make changes/corrections.  Use the Full Editor to add/delete pictures, text effects etc.

Edited by Miles
Link to comment
Share on other sites

This is how I wired my 72 240z for a SBC V8. You may/may not wire differently, but these are the functions of these wires. Before I took the stock engine out I verified the function of each wire with a volt meter and made a wire list. As you test each wire note the position of the ignition switch.


GRN - WHT:   This wire is energized by the ignition switch position just before the starter position.  I attached it  to the fuel pump side of an oil pressure switch so the fuel   pump will operate during starter operation. When the switch returns to the "run" position this wire is de-energized.

BLK-WHT without protective sleeve:    TACH terminal on HEI distributor. Used only with 280Z tach.

BLK-WHT with protective sleeve:    BAT terminal on HEI distributor

YLW-WHT:    Water temp gauge

WHT - RED (thick):    Alternator terminal. Use 14 ga. Fusible Link.

WHT:    Positive terminal on starter

BLK - YLW:    Starter S terminal

Edited by Miles
Link to comment
Share on other sites

The path goes like this: Ignition switch -> ballast resistor -> Tach -> coil (+).  With a "jumper" to bypass the ballast when the ignition is in the start position (coil gets full battery voltage in start position).  


SO...  There's a B/W that originates at the ignition switch - with the switch ON it'll have battery voltage (if the other B/W and G/W are disconnected - they will have 0V...)  That B/W connects to the ballast.  The G/W connects to the other side of the ballast and feeds the Tach.  The remaining B/W comes from the Tach and connects to the coil (+).  


In the harness, there's a G/W that "tees" into the G/W that goes to the ballast.  It's connected to the "start" signal.  So in the start position full battery voltage goes through the Tach and to the coil.  It's not a concern at the coil area.


It's a current sensing Tach, so I believe it needs to run through the ballast resistor to be accurate (If it didn't matter, I don't know why Nissan would run wire all the way from the ignition up to the coil area (ballast), then ALL the way back to the Tach, and then ALL the way back to the coil...)  But, the earlies aren't my strong point.  IDK if the ballast can be bypassed (eliminated) and have the Tach operate correctly.

Link to comment
Share on other sites

Thanks guys for the replies. Miles, the spread sheet you attached indicated I should find three wires over 125 inches long. I only have two. That convinced me to revisit b/w that is short ,and which I said was not cut.I compared the spade connector on it with the one on the g/w, and although it was very well done, which made me think it was factory, I can now see it is not factory. Mystery solved!

Thanks again. l knew I would get what I needed from members of this forum.

That spread sheet might be a candidate for a sticky some where.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...