Hi,

 

I try to find out how I can add relay for '75 280z.

When I googled, I only find this one might be accurate info.

http://forums.hybridz.org/topic/91938-headlight-relay-for-260-280/

 

When I trace FSM headlight diagram looks like this.

 

 

 

 

I'd like to add two relays. I'm not sure this is the correct way to add relay.

Could you give me advice?

 

 

Thanks in advance,

tamo3

I prefer to bring the new positive lead into the 87 pin. If you bring it into the 30 pin, then the 87a pin is hot when the headlights are off, giving you a chance to short circuit and blow the headlight fuse. Otherwise, the second drawing is correct. I hope the picture below helps some more.

Hey Tamo3, what program did you use to create your custom wiring diagrams? 

Here is another way to look at it.  Gives you the before and after picture so you can visualize the changes.

 

Headlight_relay.pdf

I notice that nobody has a relay between the headlight power switch and the fuse box fuses EDIT - as another option.  The switch is the part that tends to get pitted and hot and cause the solder joint to break.

 

I put a relay in front of the fuse box to take the load off of the headlight power switch.  It's easy to get to for 1976, it's the red wire at the fuse box that feeds the two headlight fuses.  Looks the same for 1975.  I assume that for 1975 you would have to use the shunt supply to keep the ammeter working right, basically replacing the headlight switch with a more durable switch (the relay).  76 has a voltmeter so I just ran a fused line from the battery.

 

I also did the same for the running lights but it was more difficult.  The wires are buried up in the dash.

 

I had a pretty big voltage drop across the switch and eventually both solder joints, HL and running lights, broke/melted.  The contacts in the switch had matching pits and bumps making for a tiny contact area.

 

Edit 2 - the two relay way would be best for taking the load off both supply and the dimmer.  I went with the one, in the cabin, because it was easy and I didn't really see any problems with the dimmer switch.  I wonder if the dimmer contacts really are much of a problem in the circuit?

Interesting thought. You would have to intercept the R & RY wires coming out of the fusebox at the connector and send them to the 85 pin. Connect the 86 pins to the high/low beam switch. Then you could connect the R & RY wires downstream to fuses and to the battery. Have the 87 pins on the relays hooked to the RB & RW wires that were removed from the high/low beam switch and ground the 30 pins.

Thanks all the feedback.

 

SteveJ,

Thanks for jump in and reviewing my drawing. However, I'm a bit confused your information.

High bean(RW), Low bean(RB) connect to 30pin, then RW and RB connect to 86pin?

Ground center wire(R and RY), then R to 85pin?

 

Hardway, 

I use Adobe Illustrator to draw the lines.

 

zKars,

Thanks for simplify schematic. That's looks good and better than mine, I think.

I found similar schematic not specific to 280z.

http://smg.photobucket.com/user/h4lights/media/headlightRelay240Z.gif.html

http://forums.pelicanparts.com/uploads18/944+headlight+relay+harness1289593946.jpg

http://www.jeepfan.com/projects/HeadlightRelay/relaycircuit.jpg

http://www.geocities.co.jp/MotorCity-Circuit/1623/01vmax_images/07hlb/hlb_kairozu.gif

 

Zed Head,

Interesting idea.

I think dimmer connection is for mainly earthing for the main switch if you run wire what zKars suggested.

Adding those two relay will avoid going high Amp through headlight switch and directly run high amp to the head light.

Here is the update of the schematic.

 

I was just suggesting the simplest way to get rid of the main problem with the headlight circuit.  The switch on top of the steering column, with its old, pitted contacts.   I have a single relay that only bypasses the headlight power switch.  I left the dimmer switch intact since it doesn't seem to be a problem, besides getting stuck open occasionally (in the past for me, no problems since).  I'm just being super-economical.

 

Looks like there are many ways to take the power switch (supply), and the dimmer switch (ground), and the old wires out of the circuit and replace them with new.  

Here is the update of the schematic.

 

75-280z-headlight_v3.jpg

Hi Tamo,

I like you circuit diagram. Clear and easy to follow.

There is omly one thing I would add to it. More for safety than anything else. Please don't take it as knocking what you have done. I like it a lot and may just follow your steps.

I see you are using one 30A fuse to power the high and low beam circuits. I would prefer to use two seperate fuses. Just don't like the thought of cruising down the road doing 140kmh and all of a sudden have to "feel" my way in the dark.

Looking forward to seeing photos of the finished work.

Chas

Hi Zed Head,

 

I totally agree with you. There are many way to solve the problem with adding relay. Since my car is under construction, remove all dash, I think this is great opportunity to upgrade. When I had 240z, I felt the headlight was so dark. For my 280z, I haven't drive the car yet . Once complete rebuilding, I will start working on the replay upgrade. My plan is similar approach with you. Simple way.

 

I assume I can just cut and add some wire in engine bay to add relays :-)

 

Hi Chas,

 

Thanks for the good advice. I originally put 30Amp fuse for each relay, but when I search other example, most of the schematic shows just one fuse. So, I removed it. Your recommendation is totally make sense, I will update schematic with it.

 

Thanks,

Takashi

Unless you are using 10 AWG wire, use a 10 A fuse.