P&P Headlight Relay Harness upgrade for 75-78 280's. Any demand?

[zKars]

So I find myself building a headlight relay upgrade harness for the 71 project car I'm working on. I've been making my own for a long time, can't justify the $158 USD cost of buying one from MSA. Especially with the exchange rate the way it is. 

While building this one, it reminded me that a friend had asked me to build him one for his '76 280 last fall, so I thought I should do two at once and save a bit of time. Then I remembered the "detail" that makes the 280Z harnesses a royal pain. There are no sources for the round 4 pin weatherproof connectors that the 280's use to make the harness plug and play. You are forced to hack into the harness or replace the plugs with 240 style plugs (not simple, and removes important weatherproofing). Yuch!  Can't just hand him the harness and say "go plug it in". Has to come in and get it "wired in".  

So naturally I started doing a bit of research trying to find a solution. It's not simple. Those round weatherproof plugs and pins are just not out there to just go and buy at any price.

But my question, my "raison-de-etre" for this thread, revolves around a central question. This has been such a long standing issue, and so many people have used the Dave Irwin (Zs-ondabrain) inspired harness on their 240's (did you know he started that back in 2005? 10+ years!), have the 280 crowd just given up hope and moved on, or is there a huge buildup of "if only there was a solution!" seekers out there that would jump on such a thing if it were available? I haven't seen more than a couple of theads from 280 owners wrestling with this over the years.

So what's the feeling out there? If there was a plug and play solution for 280 owners, would there be 5 intested parties or 500? Are 280 owners more likely to just be happy with a "hack the harness" solution than us prissy fussy 240 owners who insist on totally reversible "no-hack" upgrade solutions? 

[Zed Head]

I can't remember the details but I think that the 240Z and the 280Z use different methods for powering the head lights.  The dimmer system is different I believe.  Dave Irwin wrote a few posts about how a 280Z relay setup would be more difficult than the 240Z setup, if I recall right.  I think that he offered but didn't get a bunch of takers.

I've looked at mine and I think that you would need three relays - one for power to the lights, and one each for the grounding of each filament, high beam and low beam.  The extra difficulty, besides the fact that 280Z lights don't seem to be as bad as the 240Z lights might be the reason Dave and nobody else has put one together.  Plus the fact that Dave Irwin has a 240Z, not a 280Z.

I put a single relay on the power supply side for my 280Z, and find that the grounds in the dimmer switch don't really need any help.  So, one relay in front of the fuse box takes the load off of the switch on the column, and the dimmer switch doesn't have much resistance to worry about.

The running lights are a different story, I had to dig up in the harness to find the power supply wire to get a relay installed there.  Those are the two contacts on the 280Z column that get hot and pitted, the running lights and the headlights.

Anyway, if you search back through Dave Irwin posts and check the 280Z diagrams you might change your mind.  Or decide to go for it.

[zKars]

I don't see any difference in how the 240 or 280 circuits work. The HL switch on the combo turns on power to the pair of fuses in the fuse box (L and R), which then power the common terminal of each head light through the R and RY wires. Then the dimmer switch grounds either the High or Low beam side to decide which is on at any time.  The only true difference is the dedicated HL fusible link on the 280z.

The only slight year related difference is in the early 70-71 switch where the HL combo switch acts on the GROUND side of the circuit, at the center common line to the dimmer switch, while the battery + side power is hardwired to the two fuses in the fuse box.  The dimmer still grounds either the HB or LB side of the head lights. Even the harness wire color codes out to the head lights stay the same across all years. I'm pretty sure the early issues were totally about the lack of connector availability.

While there other ways to approach this problem, including the one you mention to just put a relay at the HL combo switch contacts, Dave's harness that puts the relays way out at the headlight connectors, and moves the power supply directly to the battery, is the best overall solution for one very important reason.

It removes high current requirement (and the resulting voltage drops and heat buildups and failures) from ALL switch AND harness connections AND fuse box fuses areas in one fell swoop. All components (switches, fuses, connectors) are reduced to relay trigger level power levels, which even the worst condition stuff is capable of handling. The only areas the user has to improve, clean or replace might be the pin contacts at the head light connectors where the new harness splices in.

  

Edited January 24, 2016 by zKars

[Zed Head]

Maybe it's just the connection points then.  Found some of your old posts on the subject.

Good luck.

[Chickenman]

I'm wondering if they upgraded the wiring size on the 280Z and used heavy duty contacts in the TS switch? I'm thinking they have. I've got a 1976 280Z with the factory wiring and the lighting doesn't seem to be an issue. Mind you, I have upgraded the alternator, cleaned all the terminal connections with Weicon Electrical Contact Spray ( awesome stuff ).  Cleaning the electrical connections up front made a big difference. I'm also running Cibie H4 headlights, and those were really bright after cleaning the connections.

I'll have to check the voltage drop one of these days.

[Chickenman]

If I was replacing the plugs, I wouldn't go with the early 240z style. I'd use modern Deutsch connectors. Assuming you aren't worried about authenticity.

I'm using Deutsch connectors on some of my AC connectors. Much more reliable and weatherproof than the factory parts. .

 

[zKars]

19 minutes ago, Chickenman said:

I'm wondering if they upgraded the wiring size on the 280Z and used heavy duty contacts in the TS switch? I'm thinking they have. I've got a 1976 280Z with the factory wiring and the lighting doesn't seem to be an issue. Mind you, I have upgraded the alternator, cleaned all the terminal connections with Weicon Electrical Contact Spray ( awesome stuff ).  Cleaning the electrical connections up front made a big difference. I'm also running Cibie H4 headlights, and those were really bright after cleaning the connections.

I'll have to check the voltage drop one of these days.

The wiring is definitely upgraded in the 280, all the way to the weather proof connections up front, but not the headlight OR high beam switch contacts. The switch bodies and contacts inside appear identical across all the years. When clean and new they can carry all the current for H4's no problem. But we all know what happens with age....  (my contacts aren't very clean either hahahahahah)

[S30Driver]

What about the change from the 9 to 10 pin harness connector that the 77 / 78 280's have?  Can Dave's parking light harness just be re-pinned at that end to utilize the 10 pin connector?  That at least gets the parking / dash lights upgraded with relays.

[zKars]

Dave's (and MSA's) harness does not deal with the under dash combo switch harness at all. It "splices in" to the harness up front at the two head light connectors in front of the rad. This makes it possible to work with all the various 240 switch types, 

It "could" work just fine with the 280's as well, but the problem is with the new round, 4 pin (only three are used) weather proof connectors on the 280's. No one (including Dave) has found the plugs to build the head light harness to connect in at that spot. This is why I have seen discussion about putting the relays into the harness at the combo switch. But as you mention, there are differences in the plugs across the years at the switches.  

Anyway, I'm working on a solution that everyone will like. Simple, cheap(ish), high quality and retains ALL of the advantages of the original harness design. 

Edited February 1, 2016 by zKars

[Captain Obvious]

You could still do P-n-P if you were to plug into the connectors that attach right onto the back of the headlight bulbs themselves. (And as a matter of fact, using that technique, I think you should be able to produce an auxiliary harness that would work on any 240, 260, or 280.) I haven't drawn it up, but assuming you are pulling power and ground directly from the battery with new wires, you should only need to make connection to one of the original bulb connectors. Both of the original connectors would be disconnected from the bulbs, but you could leave one hanging (or snipped off and taped up).

You would, however, have to deal with the unavailability of the headlight bucked grommets which will turn to dust with that much agitation.  

[zKars]

Interesting idea Cappy, you are correct. The headlight bulb connection is universal to all. Could just buy the Black Dragon or ebay generic headlight relay harness. But..

I think the issue of dealing with the difficulties of accessing, removing ($*&%$# rounded headed philips bolts...) and modifying/resealing the headlight can in the wheel well to get this wiring in place makes this a less than desirable solution though. I think our friend Steve with  www.240zrubberparts.com is making that grommet now, so for the industrious, it might be workable. 

Nothing quites beats using the harness connection point. If only there was a way...  

 

[Captain Obvious]

Yup. I agree that using the original harness connection points would certainly be more desirable, and it sounds like you've got some sort of plan in the works. So I'll wait quietly and patiently to see what you're working on.