So I have had my passenger headlight work intermittently for the past month or so. At first it would be "slow" to turn on (take just a second or two longer than the drivers side headlight). One time I was driving at high speed and it turned off (I was thinking vibration may have played a role). By flipping my headlights off then back on again I was able to sometimes get it to turn back on again.

Now it won't turn on at all (good thing I don't really drive at night!). I had initially thought the headlight was on its way out and then died. So I pull the headlights and check for continuity using a multimeter. It checks out.

I switch the headlights. The passenger headlight worked in the driver's side. The driver's side headlight did not work in the passenger's side. High beams work for both sides.

I busted out the multimeter on the 3-prong socket. On low-beams, the top prong gives 12V for BOTH passenger and driver's side sockets. This means the headlight is getting power.

Here is the problem... took me a while to figure it out. When I check for resistance (everything off) across the prongs on the socket, the driver's side shows no connection between each of the 3 prongs with each other.

The passenger's side, however, has 0 resistance between two of the prongs (the left one and the right one). I am not sure where this short is coming from... the wiring hasn't been messed with as far as I know.

Any ideas??? I have read that it could be the switch in the steering column, but doesn't that usually equate to no power going to the socket? I get power just fine... just not sure about this "short" ??

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Justin
1986 Z31 NA 2+0

I'd just swap out the switch and see what happens, then try to find the culprit if it doesn't fix it. Had to drive around with my high beams on all the time in my old 84 before I decided to fix it.

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1984 Z31 Turbo

Small update...

I couldn't get the steering wheel off. I tried to use a puller and it started to mangle the momo hub. hmm.

I did some more digging with the multimeter though.

right side prong = ground connection
left side prong = hi-beam positive lead
top prong = low-beam positive lead

When I switch the low-beams "on", I get +12.25V between the low-beam and the ground prong. When I switch hi-beams "on", I get +12.25V between the hi-beam and the ground prong. This is the case for both sides. It appears to function fine...

When I connect only the top and right prongs to the headlight (just low-beam + and ground prong), the headlight works fine on the driver's side. I tested the voltage between the two connections plugged in and it reads +11.5V. When I plug in just those two connections to the headlight on the passenger side, it doesn't turn on and I get 0V between those two prongs.

So for some reason it works fine without a headlight plugged in and it doesn't get power when the headlight is plugged in. Why the heck would this happen??

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Justin
1986 Z31 NA 2+0

You're describing a dead-short to ground. Total loss of power, no juice to the intended target.

Feel around for heat? (It's grounding someplace). Use a compass to follow magnetic fields along the route, to see where it stops? Test UP the line, back toward the B+ voltage (the battery) to determine where you pick-up any current?

I HATE electrical Gremlins.

F

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1970 240Z

Hmm, but wouldn't a short to ground mean that I wouldn't be reading +12V between low-beam + prong and the ground prong at the socket when the head lamp is disconnected?

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Justin
1986 Z31 NA 2+0

No.
When you insert the lamp, which represents a high impedance, the circuit runs to ground someplace else. It simply takes the route of least resistance to ground. It's lazy. The lamp is the "hard" way. The direct ground is the easier way. You simply have to think like lazy electrons to find it.

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1970 240Z

Justin,
Your instincts and others are telling you what you already know:

the dreaded Z31 headlight switch...dun dun DUNNNNNNNN

there is a way to clean the contacts and there is a way to remove the MOMO hub wihtout giving it a black eye. There is also a wiring trick you can do get it to work as well...........will pm you with more details

I know you are picking up 12v on the terminal which would suggest otherwise and I have found this to be true as well on more than one Z31. It appears that when the headlight relay is triggered by the switch it causes an intermittent contact. I can't scientifically explain it but after switching headlight switches in these cars it cured the problem. It is a known failure point.....

Justin,
Your instincts and others are telling you what you already know:

the dreaded Z31 headlight switch...dun dun DUNNNNNNNN

there is a way to clean the contacts and there is a way to remove the MOMO hub wihtout giving it a black eye. There is also a wiring trick you can do get it to work as well...........will pm you with more details

I know you are picking up 12v on the terminal which would suggest otherwise and I have found this to be true as well on more than one Z31. It appears that when the headlight relay is triggered by the switch it causes an intermittent contact. I can't scientifically explain it but after switching headlight switches in these cars it cured the problem. It is a known failure point.....

Well, THERE YA GO!!!

Always ask someone who's been there, done that!

What a great Club.

Do ya think Nissan maybe issued a recall for that switch, so a dealer could maybe do this for free?

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1970 240Z

Thanks! Glad I don't have to look for wiring problems all over... phew!

Thanks Greg! Looks like your gut was right, Justin.

Except now I have to take off this hub without breaking it........ d'oh! Haha. I am definitely using some kind of lubrication on the steering splines and running a few strokes with sandpaper or so before I reinstall it...

Frank, I doubt it... the only recall I am aware of on the z31 is the injector service. There's lots of tech articles floating around about how to clean the contacts on the switch and such so I am sure if they could have taken it in for free they would've!

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Justin
1986 Z31 NA 2+0

Got the hub off.... been blasting the splines with PBlaster for the past few days. Gave the steering wheel puller another shot (tightened it up... let it sit for a moment, loosened, rotate puller 90 degrees and tried again). It finally shot off the steering column and landed in my lap. Man was that thing stuck!

I have the switch out. Ran out of daylight so I haven't cleaned the switch yet. Hope it fixes it!

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Justin
1986 Z31 NA 2+0

Boom! It was the switch! Works great now.

I didn't see any corrosion or black parts of the case (like here http://www.xenonz31.com/Headlamps.html).

However when I pushed the little metal tab down the passenger headlamp fired right up. So I carefully used a pair of needle nose pliers to bend the tab down a bit (emphasis on carefully) and it works fine.

Huuhhh still don't understand the readings I got from the multimeter.... but who cares it works! Thank you very much guys!

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Justin
1986 Z31 NA 2+0

See how clever you are!?? You fixed that all by yrslf.


Think about how much money you just saved!

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1970 240Z

I wouldn't say it was by myself... had the help of the best Z club in the nation.

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Justin
1986 Z31 NA 2+0