no headlights

[kenward1000]

5/71 240Z.  Went to drive home late at night from the SnowBall Rally in April, discovered no headlights, neither high nor low beams.  Headlights used to work, but now don't.  Trying to figure out the issue before the MotherLode 400 Rally.  My combo switch had been falling apart, suspected that was the problem.  Jay Zinc refurbished my combo switch, tested it, but still no headlights.  Pulled every single fuse I can find, including all the fuses in the aftermarket fuse block that Fitted Garage installed, they all have continuity.  Found the headlight power connector, confirmed that both filaments in both stock headlights have continuity.  No voltage detected at the mating connector, with the car running & headlight switch on.  Seems like the problem must be somewhere between the combo switch and the headlamp connector.  All other interior and exterior lights work.  Suggestions would be appreciated.  The precipitating event might be shown in this image, as snow melt caused this creek to overflow.  

Edited June 10 by kenward1000

[Zed Head]

Not sure what you mean by "mating connector" or how you are checking for voltage. 

I was going to suggest checking the wiring diagram but it's pretty confusing.  Nissan did some weird wiring stuff before they got to the 280Z.

But if you do decide to take a look it's on the last few pages of the Owners Manual.  There are some odd freestanding diagrams out on the internet that have missing links, like open blocks on the headlight circuit.  The Owners Manual seems to have a complete diagram.

Page 37.

https://www.classiczcars.com/files/category/17-owner-manuals/

 

 

[cgsheen1]

The headlight circuit is fairly straightforward. Disconnect both headlights from the harness just in front of the radiator core support (easier than pulling the plug from the back of the headlight bulbs). With the headlight switch in the ON position:

Right side: You should read battery voltage on the RED (R)wire. 

Left side: Battery voltage on the RED/YELLOW (RW).

Continuity check: You should have GROUND continuity on either the RED/WHITE (RW) OR RED/BLACK (RB) depending on the position of the dimmer switch. This will be the same on both headlights. The ground continuity should switch wires when you pull the dimmer switch.

At least one of these things will probably NOT be true because your bulbs don't light - but you need to know which.

https://www.nicoclub.com/datsun-service-manuals has the 1971 240Z Supplement which has the electrical diagrams at the end.

From the electrical diagram you'll see that the dimmer switch operates on the GROUND SIDE. The switch gets it's ground from the Lights/Wiper Combo Switch. Power comes from the battery through the Combo Switch -> fuse box (one fuse for each headlight) -> bulb (with several connectors in between all that).

Edited June 10 by cgsheen1

[Zed Head]

Just for fun, here's what I was looking at.

and

[Zed Head]

Here's the clearer version from cgsheen's source.  And a link to the Supplement he mentioned, where the graphic below came from.  I had it, just picked the wrong source from my computer.  It's here on CZCC also.  

Edit - actually I see that the Supplement has the empty block under position 2.  Looks like a typo.  But the two images together should be useful.  Good luck.

Edit 2 - never mind I see how the empty block works.  Still confusing to me though.  RB and RW head through the Dimmer circuit and back through the Combo switch, if B is black for ground.  It looks like the Combo switch is after the Dimmer circuit to complete the ground.  Different.  Anyway, I have no incentive to solve the puzzle.  Double good luck!

https://www.classiczcars.com/files/category/11-240z/

Edited June 11 by Zed Head

[kenward1000]

After some bench testing, think that at least one of my headlight relays has failed.  I'll replace them and see what happens.

[Zed Head]

240Z's didn't come with headlight relays.  More to your Z than it came with from the factory?

 

Sorry to muddy up your thread.  I got spoiled on my 280Z.  You could follow the diagram easily.  From power source to ground.  I can't get a grasp on those 240Z diagrams.

[w3wilkes]

3 hours ago, Zed Head said:

240Z's didn't come with headlight relays.  More to your Z than it came with from the factory?

Like me, many 240Z owners have installed the "Dave Irwin" plug and play relay setup for the headlights. They should have documented it if they did this to the car. If done per the instructions it is completely reversable to stock.

[siteunseen]

I've been driving mine in daytime only after reading over and over of Mr Irwin's upgrade. I don't use the headlights or wiper blades until my lazy self installs his updates. Hasn't been an issue so far as I only get to drive it on occasion but still those, hopefully still available, are a must on my 240.

[Terrapin Z]

I have DI's headlight and rear light harnesses. Both work great. H4's in the front and the rear kit really brightens up the sides and tails. 

I had heard he stopped making them and now MSA carries similar harness kits. 

[kenward1000]

Replaced both of the headlight relays but still no headlights.  Next will test to see if the connectors that the relays plug into, have battery power and then trigger power when the combo switch is set for headlights.  

[Yarb]

What is the voltage you are measuring at the relay from the fuse box?