How much wattage can stock headlight wiring support?

[AK260]

Agreed. I didn't put my relays in the interior (they are out in the engine compartment), but I used four relays. One per side per beam. Not only is it a more fault tolerant system, but it also minimizes the voltage drop in the switching system. Down sides are the obvious cost and complexity, but relays are cheap and the complexity is a once and done thing.
With the relays, I find my old original incandescent bulbs to be quite enjoyable on a dark road.

Funny you should say that, my father in law’s TR4A and Volvo 123 Amazon are both relayed up and the light output with the 25% brighter bulbs is really quite impressive / plenty good enough. So I can see the Z lights working well if relayed.

Even though I run LEDs and will likely never go back, I have to admit that on a classic car, the warmer light of the incandescents “looks” better / far more age appropriate - but that statement is only valid if you can actually see the road well enough. ;) My philosophy for any improvement to the car is always a case of safety / driving experience first, originality second but the car has to “appear” as stock as possible where possible, until of course you give it the beans.

But to the OP’s original question, while the car’s own wiring is man enough to power the headlights, you can’t beat new wiring and connections through relays or the protection they offer for your stalk connectors.

[Captain Obvious]

I'm skeptical about the validity of taking photos out the windshield showing how my headlights look, but if I get the chance, I will do that. I'm not sure it'll add any value without having a fixed "point of reference", but I'll give it a shot. The best thing would be to have your car next to mine and we could compare. We should figure out a way to make that happen some time.  

I did my 280Z relays using a hybrid method of old wiring and new wiring. I'm still utilizing the original fuses in their original location, but the switches on the steering column are only controlling relay current now, not the high headlight current. So for me, one of the nice things is that the two headlight fuses in the fuse block are still labeled correctly, one per side.

[Yarb]

@Captain Obvious In Your spare time😀.Would you be kind enough to create a rough schematic of your relay install. Also curious on where you located the relays. I’m waiting on other parts to arrive so this would be a good time to go ahead and do the headlight relay upgrade. No Hurry of course!!

[AZDatsun]

Adding onto this... on my 78 when I turn my headlights lights on the green/white wire going into my combo switch gets hot to the touch. Is that normal? If not where should I look to fix that?


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[heyitsrama]

23 minutes ago, AZDatsun said:

Adding onto this... on my 78 when I turn my headlights lights on the green/white wire going into my combo switch gets hot to the touch. Is that normal? If not where should I look to fix that?


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That’s the sign that you need to do a relay upgrade before the combo-switch melts. 😳 burned my hand real good on my first car when I found that out the combo switch gets hot.

[AZDatsun]

I just looked at the schematic looks like green/white goes to the following but not the headlights..

Side markers
Turn signal/parking lights
All Gauges lights
Ashtray lamp
Radio light
Tail lights
License plate light
Cigarette lighter light
Glove box light
Hazard switch


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[Namerow]

Beware.  Normal assumptions don't work.  My 70 Z's wiring demonstrated significant damage to the existing wiring close* to the headlight connectors (* up to 2" of contaminated/burned/almost smoked wire).  That damage means increased resistance.

[Zed Head]

14 minutes ago, AZDatsun said:

I just looked at the schematic looks like green/white goes to the following but not the headlights..

Side markers
Turn signal/parking lights
All Gauges lights
Ashtray lamp
Radio light
Tail lights
License plate light
Cigarette lighter light
Glove box light
Hazard switch


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The running light solder joint fails also.  Too much heat, too many extreme heat cycles.  You can put a single relay after the combo switch to power the various lights and take the load off of the switch.  On my 76 it was a blue wire up under the dash.  Hard to get to.

I used a single relay on my headlight circuit also.  It's easy to do and will save the combo switch while you're pondering the more complex solutions.  Once that solder joint fails it tends to keep failing, I found.  I just patched it with new solder a few times but I think a proper desoldering and cleaning is the way to go if you want to run full current through it again.  It's a pain, avoid the broken solder joints if you can.

[AK260]

I'm skeptical about the validity of taking photos out the windshield showing how my headlights look

Fair point - how about this for comparing LED v Old skool ....

I did my 280Z relays using a hybrid method of old wiring and new wiring. I'm still utilizing the original fuses in their original location, but the switches on the steering column are only controlling relay current now, not the high headlight current. So for me, one of the nice things is that the two headlight fuses in the fuse block are still labeled correctly, one per side.

I utterly love this idea and will copy you!!! [emoji106]

[SteveJ]

11 hours ago, AZDatsun said:

Adding onto this... on my 78 when I turn my headlights lights on the green/white wire going into my combo switch gets hot to the touch. Is that normal? If not where should I look to fix that?


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Start by swapping out the incandescent bulbs for LEDs.

Here is some trivia I documented on this site, and no one seemed to notice. The bulb spec in the FSM calls out bulbs that appear to be NLA. Pretty much all of the BA-15 bulbs these days are 1156 and 1157. They are a slightly higher wattage (and more current draw) than the 1034, 1073,  and 67 bulbs called out in the 74-78 FSMs. The added current draw is not enough to blow the fuse, but it is enough to warm up all of the areas where some corrosion might have built up over 40+ years. Adding to that, IMHO, that circuit does not have the proper gauge wire. It's protected by a 20A fuse! In the control circuitry that my company manufactures, we never go above 10A fuses for 14AWG wire.

After you swap out for LEDs, you might need electronic flashers. I have been using this type for many years: https://www.amazon.com/dp/B07F1M9579

Also change out the parking light fuse from 20A to 10A. The current draw with LEDs is a small fraction of where it was before. The 10A fuse will protect the wiring better. (This is experience talking here.)

Here's the link to my post on current draw for the parking lights: 

 

Edited November 17, 2020 by SteveJ
Added link to another post

[cgsheen1]

On 11/14/2020 at 6:41 PM, AK260 said:

My stock wiring with LED bulbs in H4 lenses...



1/3 current of halogens, no relays yet, transformed night time driving, ‘nuff said!

Yup. I did that too. Awesome upgrade from H4's.

So bright I had to make sure my headlights were aimed properly... 😎

[AZDatsun]

Well I figured out my green/white wire heating up with lights on issue. I noticed the heat really was starting at the plastic connector at the bottom of the steering wheel. I inspected it and there was a brown burn mark. I cut the green white wires on both sides of the connector and spliced in a new wire to connect them bypassing the wire harness connector. Now no more heat.. maybe it was a poor connection in the connector causing resistance. I am going to still change to LED though thank you !


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