A Different Headlight Relay Upgrade - 4 Relays

[Captain Obvious]

Yes, I encountered those splices buried inside the harness. I think the wire sizes may have changed from year to year though. My wire sizes (1977) were the same from the passenger compartment all the way out to the bulbs, including beyond those splices. In other words, I got a large R/W coming through the firewall and heads towards the front of the car. Near the RF corner, that large R/W split into TWO large R/W's of the same gauge (on my car). Sounds like yours didn't do that.

 

Anyway, if you've got the flexibility to mount the relay block up near those splices, it could simplify the installation. Hopefully I'll get a chance to draw up a couple sketches today.

[Namerow]

Yes, exactly.  For my June 1970 Series 1, I have 10G and 12G wires that run all the way from their firewall connectors to the LHS headlight connector.  At the splicing points on the RHS of the engine bay, the take-off wires for the RHS headlight each go down in gauge by one step (i.e. 12G spliced off of 10G, 14G spliced off of 12G).  The upstream splice-in locations for the RHS headlight wires were perhaps an attempt by Nissan designers to balance the net wiring resistance, LHS vs. RHS?

[Captain Obvious]

So it definitely sounds like there were subtle some gauge changes over the years in different spots. My splice points are in the same location as yours, but none of my gauges changed. In other words, the short stubs going to my RHS bulb are the same gauges as the long runs from the firewall. I'm guessing that it was cheaper for them to use the same size gauge there instead of taking the time and effort to use a different one. A tiny bit more costly in terms of copper, but faster to manufacture.

 

And as a matter of trivial interest, the wires on my pigtail that goes with my 77 headlight bucket are also the same gauges. I've heard that may be different on other years as well. There's no reason they couldn't have reduced the size, but for some reason, by the time they got to 77/78, they didn't bother. They just kept the gauges the same. My theory is that when they went to the 77/78 round style headlight connectors, the needed a larger wire to fit comfortably into the larger crimp contact. The choice of gauge may have been driven by a choice of connector used.

 

As for the location of the splices being upstream, I don't think it has anything to do with balancing resistances. I think it's all mechanical.

 

They wanted to spur off the RHS headlight stub, but they wanted it to be mechanical sturdy. So they put the splice some short distance upstream so by the time they got to the pick-off point, they had several wraps of tape to support the wires and not put any mechanical stress on the splice joint. Also gives them the opportunity to insulate the splice point inside the harness without having to deal with insulating it AND branching off the stub all at the same time. I wasn't there, but that's my read.

[TomoHawk]

I should've done all this stuff when the engine was out...  I suppose removing the hood, bumpers, and fenders will allow you to get in there now.

Edited June 6, 2015 by TomoHawk

[Namerow]

TomoHawk, the engine is still in my car as I'm doing this work. Fenders, hood, grille, front valence panel and front bumper are also still in place.  I have, however, done a partial strip of some of the engine compartment stuff -- radiator, hoses, brake lines, alternator, etc.  Removal of the rad is key. If the rad was still in place, it would be very difficult (altho not impossible) to get at the wiring harness and connectors that lie along the front of the rad bulkhead.

[TomoHawk]

If you've done that much, the removing the hood should be easy.

Edited June 29, 2015 by TomoHawk

[Captain Obvious]

Well it might depend on the year, but I found it very easy to remove and reinstall the harness without any major disassembly of other items. The only thing I took out that required any significant effort was my EFI air cleaner. I didn't have to mess with the radiator, hood, or any of that stuff. YMMV

[Namerow]

Some questions for Captain Obvious:

 

I'm trying to adapt your 4-relay scheme to a May 70 Series 1.  Its wiring arrangement seems to be pretty much in agreement with the second of the two electrical diagrams that appear at the end of the 1971 FSM 'Supplement' (specifically, the schematic that's labeled, 'Late Model S30 Series for USA').

 

I have questions relating to the re-jig of the Combo Switch wiring that you've shown earlier in this thread.  Your instructions and pix discuss to two main objectives:

 

1. Make the Dimmer Switch switch to ground

2. Make the 'Headlamp' fuses always hot

 

Your instructions appear to be specific to a Series 2 and/or Series 3 car.  Certainly, your discussion of the Combo Switch wiring colours is quite different from what I find on my Series 1.  I've read that there was a switch in electrical 'design philosophy' on Nissan's part when they updated things for the Series 2 launch.  Specifically, the Series 1 headlights circuit used a 'switch to ground' approach.  The Series 2 and Series 3 evidently do not, hence the re-worked Combo Switch wiring that you discuss as being necessary to make your scheme work.  (BTW, I don't think the change had anything to do with overheated fuses and overworked switch contacts, because that didn't change for the new design.  I think it had to do with electrical corrosion problems that were a problem for the headlamp connector plugs up at the front of the car.  Perhaps you or someone else can comment?).

 

Anyway, looking at my car's Combo Switch, I find that the hi/lo dimmer switch 'already' switches to ground (by way of a Red jumper wire that leads out of the Dimmer Switch and connects via a bullet connector into a Black wire that goes to the back of the Light Switch and then directly to the main ground wire in the Dash Harness.

 

Also, it appears that the two Headlight fuses in my Series 1 fuse block are 'already' always hot.   They're supplied by the big White-Red wires that come to into the fuse block from the Alternator by way of the Ammeter 'NEG' terminal (Battery connects to the Ammeter's 'POS' terminal).

 

So, it looks to me like the 'Late Model S30 Series USA' Combo Switch found in my car doesn't need any re-working in order to adapt directly to your 4-relay scheme.  Would you mind having a look at the Series 1 wiring diagram to see if you agree?

 

Thx in advance for your help.

[SteveJ]

In the 70 & 71, the headlight switch completed the path to ground from the High/Low switch on the other side.

[Captain Obvious]

Namerow, Yeah, I wouldn't be surprised if there were some differences with the earlier cars and I probably should have accounted for some of that. Sorry for any potential confusion and I'll take a look at the older wiring diagram and see what I come up with.

[Captain Obvious]

Namerow, OK, I had a chance to look into the early years.

 

First, You nailed this objectives of the modifications to the combo switch: 2. Make the 'Headlamp' fuses always hot

 

However, I would make one change to the other objective (because the dimmer switch always did switch to ground). I would change the other objective to:

 

1. Make the Dimmer Switch switch to ground only when the headlights are on and not make any connection at all when off

 

Second, I found a wiring diagram in the 70 Owner's Manual (not FSM, but Owner's Manual), and it appears that what's old is new again because the 70 cars are wired such that the above two objectives are already achieved. The headlight fuses are always hot, and the hi/lo select has three states:

 

low beam connected to ground (R/B

high beams connected to ground (R/W)

no beams connected to ground (OFF)
 

Third, I found the wiring diagram you referenced in the 1971 supplement manual and there are two diagrams in it. "Basic Model" and "Late Model".

 

The "Basic Model" is wired like 70 version in that the fuses are always hot and the hi/lo beam select switches has three states.

 

The "Late Model" is wired like all the subsequent years through 78 in that the fuses are only hot when the combo switch is in the #2 position (headlights on) and the combo switch always connects one of the beams to ground regardless if the headlights are on or not.

 

Are we both on the same page so far?

[TomoHawk]

That would mean the headlamp switch would have two sets of contacts in it;  one set for the headlamp main power, and one set for the high-beam ground.