A Different Headlight Relay Upgrade - 4 Relays

[FastWoman]

I did the relay modification in my '78 entirely in the relay box area (passenger inner fender), using a strategy essentially the same as that linked by Tamo.  I was rewiring my main fusible link wires (removing all of the weird OEM junk) and also upgrading my alternator wire.  So while I was there, I simply snipped the four headlight wires, branched off to the relay housing, and added my two relays.  Since I was installing maxifuses in this project, I simply designated another maxifuse to feed the relays.  If I ever needed to go back to OEM, all I'd have to do is to reconnect the 4 wires I snipped.  With this implementation, current path is very short, and nothing needs to pass through the firewall.

Edited July 1, 2015 by FastWoman

[Namerow]

Ay chihuahua!  There's another wiring diagram!!  I forgot all about the tiny little version that's tucked into the back pages of the MY-70 owners manual (and humorously labeled, 'Minor Maintenance'...  ha!)

 

So now I've burned up another morning staring at yet another version of the wiring and connection logic for the early Z Combination Switch.  This wasn't helped by the fact that the wires on the 'Lights' side of my car's combo switch are different from those shown in all three of the wiring diagrams (see photos).  I finally decided to check the 6X connector from the dash harness that plugs into the matching connector on the Combo Switch.  Ahah!  The wire colors change as they pass across the connection.  For my switch:

 

Switch Wire    Harness Wire

      RL                  L    

      YG                  LW  

      YB                  LY   

 

So now I had something to compare with the 3 wiring diagrams.  After a lot of playing around with my continuity checker, I determined that the Combo Switch in my May-70 Series 1 is best represented by the diagram that appears in the 1970 Owners Manual that came with my car (for reference, my manual is labeled as a 20-Mar-1970 printing).

 

The fun didn't stop there, though.  Even this wiring diagram isn't absolutely accurate in its depiction of the connection logic for the Combo Switch.  The logic for the Wiper function is shown incorrectly.  In fact, if you look at all three diagrams, you'll find that the details for the Wiper function are, um, 'erratic'.  In the FSM versions, only 'ON' and 'OFF' are depicted.  In the Owners Manual version, all three Wiper positions ('OFF' / 'LO' / 'HI') are shown, but connection details are shown only for the 'OFF' and 'LO' positions, and even these are depicted incorrectly.

 

I scanned the diagram from my 70 Owners Manual and then created a modified version that depicts the Wiper connection logic the way I traced it from my actual Combo Switch.  Combo Switch details from all four versions are shown below...

 

So, anyway, I've now verified that my particular Combo Switch uses a switched ground for the headlights that is controlled on both sides of the Combo Switch...

 

• On the 'Lights' side - Ground continuity for the headlights is only established when the Light control knob is in the '2' position

 

• On the 'Turn Signal' side - The Dimmer Switch provides 3 possible ground paths/settings... Open, Hi-Beam, and Lo-Beam). 

 

And then, of course, there appears to be a 'Flash to Pass' function, which I think allows the hi-beams to be triggered by a partial pull on the T/S stalk (and doesn't care what position the Dimmer Switch is in).  Can somebody explain how that works?

 

 

But the 'Main Question', now, is this: 

 

With the set-up in my car (per the wiring diagram from the 70 Owners Manual), what do I need to do -- if anything -- to make my two headlight fuses always hot?

 

71 FSM Supplement - Basic Model

 

71 FSM Supplement - Late Model

 

70 Owner's Manual (dated 20-Mar-1970)

 

70 Owner's Manual - Wiper switching logic corrected

Edited July 1, 2015 by Namerow

[Namerow]

I should have added the full electrical diagram from the 70 Owner's Manual.  Here it is, just as I scanned it from the hard-copy manual that came with my car...

 

S30 Wiring Schematic - 70 240Z - B&W - 70 Owners Manual - v3 (darkened).pdf

Edited July 1, 2015 by Namerow

[Captain Obvious]

Cool. If your car is wired as per the diagram from the 70 Owner's Manual, then you already have headlight fuses hot all the time. So I believe the answer to the question "With the set-up in my car (per the wiring diagram from the 70 Owners Manual), what do I need to do -- if anything -- to make my two headlight fuses always hot?" is "Nothing." I believe you're good to go in that respect.

 

You can double check that by pulling one of the short pigtail headlight connectors off in the engine compartment and probing the R or R/Y wires while having the headlight switch in the OFF position.

 

If your car is wired like the 70 manual, then the R and R/Y wires to the headlight pigtails should be hot at all times, while in the later cars, those two wires would only be hot when the headlight switch is in the #2 position.

 

And I wasn't there when they designed the system, but I wouldn't be surprised if that's why they changed it in later years. It's less safe and less fault tolerant to have those wires hot at all times than to have them only powered when the lights are on. I'm not sure that's why they went away from that early scheme, but if I were designing the wiring for the car, I would have tried my best to never have anything hot at all times unless absolutely necessary. It's just safer when it's dead.

 

So else can we do on the headlights? Are you OK at this point? Current round of questions answered?

 

On Edit - And BTW - Thanks for culling the 70 diagram out of the owner's manual. I've got the whole thing in pdf, but it's much more convenient to have the wiring diagram pulled out and separate in it's own file.

Edited July 1, 2015 by Captain Obvious

[Namerow]

Thanks for the quick reply, Captain O (and thx also to Steve for chiming in on my original question).  I wanted to be 100% sure before I start cutting and soldering for my 4-relay set-up.  The two FSM-sourced electrical diagrams just didn't seem to line up with what I had in front of me (nor did the one from the Haynes workshop manual, or any of the other permutations that I've found on this site), so I'm really happy that you reminded me about the one I had sitting in a drawer in my Owner's Manual.  

 

Some trivia I noticed during this exercise:

 

• The wiring diagram in my 1970 Owner's Manual shows the #2 fusible link (at the Alternator) that the 71 FSM diagrams managed to omit
• Unfortunately, the 1970 OM diagram doesn't show the Accessory Relay that powers the Rear Defrost heating grid (although it at least shows the grid and switch)
• The 1970 OM diagram also completely omits the Blower wiring and control switch
• The 1970 OM diagram has the pairings of the aux gauges mixed up (should be Amps/Fuel + Water/Oil, not Amps/Water + Fuel/Oil)

Also:

 

The embossed graphics for the Light/Wiper settings on my Combo Switch show a third (but unpainted) 'dot' for the Wiper speeds, hinting that Nissan was already planning to add an 'Intermittent' feature at some later date.

 

Counting those in my 'spares' box, I have four Combo Switches on hand.  They're all different!

[Captain Obvious]

Great. And thanks for the early wiring diagram trivia. Earliest year I've ever personally taken a wrench to is a 74 but I like that trivia stuff anyway regardless of the year.

 

So before you go cutting any wires... I still believe it should be possible to do a four relay option without cutting anything by plugging into the stock connectors. Especially if your car is already setup with fuses that are hot at all times and a beam select switch that has three states,:

 

Hi to ground

Low to ground

No connect

 

I know I said I would look into that a while ago (and didn't), but give me another day or so before you start cutting into your harness. I might be able to come up with something more plug-n-play.

[Namerow]

Already with you on that.  The design I've come up with uses an 'intermediate harness' with Nissan T-3 connectors to plug into the engine harness at the appropriate places (when I said I was going to start cutting wires, I was talking about the wires for this harness and not about cutting into the car's engine harness).

 

BTW, a recent search through the local pic-n-pull produced a very nice relay block, taken from the engine compartment of a 91 Mazda MPV.  The casing has removable upper and lower caps, with all of the wiring entering and exiting at a common conduit at the front.  The internal wiring and relay set-up was, of course, specific to the Mazda application.  However, the wire terminals can be extracted from their sockets and moved around to suit a new requirement.  I grabbed two of these relay blocks and have used them to produce a single block with 5 identical relays (4 for headlights, 1 for fog lights, one empty socket for possible future use for an electric engine cooling fan). 

 

 

The new, intermediate harness will be connected up to the relay block using two pairs of spare Nissan 3x2 connectors.  The fog light relay will take its switching signal off the rhs pair of bullet-connector plug-in points up at the front of the car.  Power for the fog lights will come off the alternator.  Headlights and fog lights will now all be grounded to the chassis with dedicated local ground wires.

 

The relay block will be mounted in the engine compartment, using the mounting bosses from the now-discarded voltage regulator (I'm using a 280ZX internally-regulated alternator, along with the MSA/Dave adaptor plug).

Edited July 2, 2015 by Namerow

[TomoHawk]

This stuff makes me wish my fingers (12 numb thumbs ) had that ol' magic from my younger days, when I could solder 34ga wires with silver in a tornado....

[Captain Obvious]

Sounds like a plan. One of the things that I like about having the fuses always hot and doing all the relay switching on the low side is that you need to bring one less wire to the relay block. You just connect one side of the relay coil to one side of the contacts. You can just daisy chain the R (and R/Y) wires to two connections on the same relay which results in less wires to the rest of the car.

 

I like that relay block from the MPV. In another thread, there was some discussion of pre-existing relay/fuse blocks that could be harvested from other cars, but that one didn't come up. So the MPV block has spaces for six relays, all the same style? Any fuses in the block, or just relays?

 

I would use one of the other relay positions for a starter relay to take the load off your ignition switch. If you're doing (or have done) the internal regulator upgrade, it's a convenient time to do the starter relay because the internal regulator leaves you with a couple unused signals that are needed to do the starter relay. Namely, hot at all times, and ground. You can re-purpose those two connections for the starter instead of the external regulator.

[Namerow]

Thx for the additional input.  I think that's pretty much in line with what I've sketched out.

 

I'm aware of the Starter relay possibility, but haven't been able to convince myself that it's really necessary, given that the Starter's solenoid seems to be already there to serve exactly the same purpose.  Do I really need a relay to operate a relay?  Your thoughts on this?

 

About the MPV relay block: 

 

It has no sockets for fuses. Just relays.  The relays were mostly of one spec and terminal configuration, but one was quite different.  That one used a white-plastic adaptor socket at its base to match its connector blades to the basic socket configuration that's molded into the base block.  I pitched all of the oddball relays and their plug adaptors and will be using all-identical relays (made possible because I took away two relay blocks from the pic-and-pull and used them to mix-and-match to create one to my liking).

 

I couldn't find any specs on-line for the relays that I'm going to use, so I took one of the spares and levered off the protective housing.  Underneath, I found what appears to be a standard-issue automotive relay.  It uses a resistor (rather than a diode) to help protect the ECU and the other on-board computers from possible voltage spikes.

 

In its original habitat, the MPV's relay block clips onto the side of a much bigger plastic box that I'll call the 'electrical centre'.  The bigger box has a few more relays, along with many, many fuses.  Both boxes are easy to get at -- they're up top, at the driver's-front corner of the engine bay.  If anyone else decides that they like this unit, just be sure to cut the wires as far out of the relay block as you can.  I was able to get about 6" of loose wire to play with, but not much more.  Try to get two relay blocks.

 

All of those loose wire ends from the relays will receive Nissan-issue brass connector terminals, which will then be inserted back into the white-plastic Nissan 3x2 connector blocks.

[Captain Obvious]

Just in time. Here's a redrawn version of the 4-relay option with emphasis on making it as reversible as possible. And in fact, it should be completely plug-n-play for your early 240Z. This scheme would work in the later cars as well, but it wouldn't be quite plug-n-play because you would need to do the under dash changes to make the fuses hot at all times and give the HI/LO switch the three states required. But since your early 240 is already wired like that you're ahead of the game! Who knew?

 

So for an early 240, this should be plug-n-play, and "almost plug-n-play" for everything else:

The only thing that makes it a little more complicated than the tradidtional 2-relay version is that you need to make connection to the driver's side headlight connector off the harness to pick up the R/Y wire. The traditional 2-relay version does not require any connections to the engine bay harness on that side of the car because it powers both relays off the right headlight side. I don't see it as a hardship though. You always have to run wires over there anyway to get to the headlight pigtail. It's one more connector and an additional wire.

 

IMHO, I think that's a small price to pay for the benefits of fault tolerance and reduced voltage drops.

[Captain Obvious]

Thanks for the additional info on the MPV relay block. Those relays are a very common form factor and can be found pretty much everywhere. In fact, I think those are interchangeable with the Honda relays that I used when I did my upgrade. The one you pictured is SPST, but there's also an SPDT version in the same form factor (with the addition of one more pin on the bottom). The headlights only require SPST, but keep in mind for other stuff that you can get SPDT as well if necessary. Don't know if the MPV block has provisions for the additional pin, but just thought I would mention it.

 

As for the starter relay... Do I think you really need a relay to operate a relay?

 

The starter solenoid wart sitting on top of the starter draws more current than the ignition switch can handle forever. Eventually the contacts inside the ignition switch will burn up and you'll get intermittent starter operation. It's not absolutely necessary, but you'll eventually be replacing the ignition switch if you don't put in a starter relay.

 

Maybe you and I will be dust by the time that happens to your car, or maybe it'll happen tomorrow (and I hope I'm not dust by then).

 

I had already had my contacts burn up in my ignition switch once and didn't want to subject my new switch to the same eventual doom. I was in there messing around with wires and stuff already and just bit the bullet and did it all at the same time.

 

Those are my thoughts. Hope that helps?