A Different Headlight Relay Upgrade - 4 Relays

[Captain Obvious]

Hmmm... I'm not sure I'm understanding what you meant, but I didn't have to pull any new wires through the firewall:

 

Original Red from the fuse box for power to right bulb relays

Original R/Y from the fuse box for power to left bulb relays

Original R/B for low beam actuation

Original R/W for high beam actuation

 

That's it.

 

The branching for different relays I did out in the engine compartment inside the harness stem to the relays.

 

For example, I needed two R/B wires to control two relays so I spliced a second R/B onto the original one that came through the firewall.  Same for the power wires to multiple relays. And since only one of them is carrying any current at any given time I feel completely justified in that. So, yes... I did need extra wires, but I did the splitting inside the harness on the way to the relays.

 

You could, if desired, make all the splitting connections by crimping multiple wires into the relay spade connectors and daisy chaining them using the crimp contacts as your junction points. I didn't do that because I didn't want to complicate the crimps, but that could work as well.

[SteveJ]

I was comparing your schematic and Jim's schematic which one is easier to deploy...

http://www.classiczcars.com/topic/50416-75-280z-headlight-relay-upgrade/?p=458629

 

post-11371-0-49828000-1415984701.jpg

 

I was wondering where is your dimmer switch?

There is a problem with that drawing. No wire gauge is specified for the added wire that has a 30A fuse. 

First, even if you used that fuse to power both headlights, you wouldn't need more than a 15A fuse.

Second, if you use anything less than 10 AWG, the fuse will not protect the wiring in the event of a short circuit.

[TomoHawk]

Bruce- OK, I got that.  I would also split or add wires in a better place than at the relay terminals.

 

SteveJ-

  You mean wire heavier than 10 AWG? "Less than" would mean something like 8 AWG...

Edited June 3, 2015 by TomoHawk

[Patcon]

8 AWG is heavier unless I am missing something.

[SteveJ]

8 AWG is heavier unless I am missing something.

In the drawing I was referencing, I did not see any wire gauges specified, nor did I see anything about wire gauge in the other thread.

[TomoHawk]

Sometimes people forget that wire gets THINNER as the gauge number goes up.  the reasoning for gauge numbers must be interesting (such as how many fit into a conduit pipe.)

[Patcon]

That was my point. Just trying to clarify.

[Captain Obvious]

I would also split or add wires in a better place than at the relay terminals.

 

Yeah, I've done that kind of thing at times, but I really don't like to. Especially for larger wire sizes. I don't mind so much crimping two 20 GA together, but much bigger than that and I don't like it.

 

So about adding completely new wires... On the 4 relay design, I did add a new R/B wire from the relay block out to one of the headlights. The original system daisy chains the filament currents together, but with one relay for each filament, you can't do that. You need another wire run to the front for one of the low beams.

 

The two relay hybrid version shouldn't need to do that however. You'll have both sides HI beams running through the R/W (the largest wire) and both sides LO beams running through the smallest R/B (just like stock).

[Namerow]

Captain O:

 

I like the 4-relay concept and I happen to have the engine harness, dash harness, and combo switch out of my car at the moment. In addition, I also plan to add the same internally-regulated alternator mod and starter relay as you. So, all good to this point.

 

I understand the details of the combo switch re-wire and the the 4-relay assembly/mounting scheme.  Pretty straight-forward. I wonder, though, if you could be a little more explicit about the wiring mods necessary on the engine harness and at the headlight connectors.  Specifically:

 

1. You talk about 'splicing' into the 'R', 'R-B', 'R-W', and 'R-Y' wires in the engine harness (apparently, somewhere in the vicinity of the voltage regulator).  However, it seems like you may actually have had to cut each of these wires so that you could then take a new lead off each wire to go to the relays.  It appears you have also added new wiring to lead back from the relays to connect into the appropriate cut-wire points in the harness.  For the benefit of us non-electrical types, please explain in more mechanical terms exactly what you did to the engine harness and what new wiring was added to/from the relay group.

 

2. In your initial circuit diagram, you say, 'Swapped terminal positions at back of bulb' and, 'Added a second R-B wire'.  Please explain in greater detail.

[Captain Obvious]

Actually, because I'm a loony, I went further than that... I bought a hacked up engine bay harness and stripped out the headlight wires. Then I opened up my original harness starting at the headlights and replaced my original wires with donor wires while pulling my original wires out as I went. I performed this maneuver until I got back to where the voltage regulator branched off.

 

So once I reached the regulator branch area, I had donor wires coming from the direction of the headlights (that were long enough to reach into the passenger compartment) and original wires coming from the passenger compartment (that were long enough to reach up to the headlights). That gave me plenty of extra length centered near the regulator to run up to and back down from where the regulator used to be.

 

That's what I did.

 

I wouldn't wish that on anyone else.

 

I'll make up some sketches of easier ways...

[TomoHawk]

Just make up your own r/b and r/w wires.  All you need is a Sharpie marker and some white-out..

 

 

Ha ha ha

[Namerow]

OK.  I'll be interested to see what you come up with.  I have a certain amount of flexibility for my project, since I had already intended to re-tape some areas of my engine harness where the original tape has hardened and begun to un-stick.

 

As you know, I'm sure, the factory design for the engine harness provides a natural tie-in point for the new R-W and R-B wires at the place (hidden inside the harness tape) where the smaller-size RHS R-W and R-B wires are spliced into the larger-size LHS R-W and R-B wires (the two splices are made about 11" upstream of the place where the RHS lighting wire group breaks out of the main harness).