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240z Headlight High Beams Toggle left to right (Video)


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Hey all,

 

I haven't had any luck finding people who have this issue so I thought I'd toss it up here to see if anyone can help.

 

Headlights work, but one side is always high beam and when I pull the high beam switch, it toggles to the other side.

 

 

https://youtu.be/xzObvNaI9yE

 

 

Its a 1973 and the wiring diagram I'm going off of is close but not exact.

 

Anyone have any thoughts?

Edited by xonix_digital
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The highbeam indicator light is always on if the headlights are on.

 

The wires on the headlight harness haven't changed and their configuration matches my wiring diagram so it would be really disconcerting to switch them around for a fix.

I'm fairly sure that something else is either hooked up wrong or there is something else that I am missing.

 

That being said, I think that what you are suggesting would make the headlights work as expected but whatever else is wrong would still be wrong.

Do I sound crazy?  :wacko:

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Seems like you either switched the high beam low beam output for one of the lights, but If I recall it should be a plug that is actually directional (3 prongs oriented in 1 way) I doubt it, but maybe you bought two of the same side if that is a thing, sealed beams would have to be oriented to prevent blinding traffic I imagine that seems odd that they would swap the outputs though. 

 

Alternatively you could have had a fault with the selector switch. It is old particle board and it can break. Although if that was the case you would probably get a failure to light rather then an alternating light situation.

 

If someone modified the sealed beams into H4's or if someone got rid of the plug it could very well be a problem at the headlight itself rather then with the wiring diagram and harness.

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So after looking into the wiring diagram a bit more it looks like both headlights have at least one wire that goes to the "Passing Relay". Note that this is different from the "Flasher" relay that ticks the signals on and off.

 

I have not been able to get a photo of this relay. There are four wires running to it according to the diagram.

Anyone got a photo of a passing relay so I can identify it in the bundle?

 

 

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Seems like you either switched the high beam low beam output for one of the lights, but If I recall it should be a plug that is actually directional (3 prongs oriented in 1 way) I doubt it, but maybe you bought two of the same side if that is a thing, sealed beams would have to be oriented to prevent blinding traffic I imagine that seems odd that they would swap the outputs though. 

 

Alternatively you could have had a fault with the selector switch. It is old particle board and it can break. Although if that was the case you would probably get a failure to light rather then an alternating light situation.

 

If someone modified the sealed beams into H4's or if someone got rid of the plug it could very well be a problem at the headlight itself rather then with the wiring diagram and harness.

 

The reason I think something is hooked up wrong is because everything worked as expected when the car was completely disassembled.

I was hoping that I had just done something silly and this was a common issue but I guess not.

 

All the headlight wiring is stock and correct. The H4 headlamps have been installed but also worked normally prior to disassembling.

Going to dive into the relay bundle now and see what I can find. 

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I'm fairly sure the North American Z's didn't have a passing relay.

 

My guess is that you have a failed H4 bulb that has connected the high and low beam circuit. Not likely but not thing you'd think might happen.

 

Since the HB switch affects both bulb circuits together, the issue must be somewhere up front in the wiring near the bulbs. Grounding either side of the switch would like both High or low beam filaments.

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I'm going to try swapping out the bulbs since they are cheap and easy.

 

Thanks all for the thoughts and ideas.

I will report back tomorrow afternoon.

 

Tonight I tried swapping out the high beam switch with the same result. Tried known good ground from the switch with same result.

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I'm fairly sure the North American Z's didn't have a passing relay.

My guess is that you have a failed H4 bulb that has connected the high and low beam circuit. Not likely but not thing you'd think might happen.

Since the HB switch affects both bulb circuits together, the issue must be somewhere up front in the wiring near the bulbs. Grounding either side of the switch would like both High or low beam filaments.

Hey z240. I'm not sure I understand what you mean by:

 

"Grounding either side of the switch would like both High or low beam filaments."

 

Could you elaborate for me? Thanks in advance.

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I really liked the faulty bulb possibility but it isn't the cause.

Swapped both bulbs and there was no change.

 

The bulbs I pulled out of there came with my cheap Chinese eBay headlights and were 90/100w. This sounds extremely high no?

I could only find 55/60w at the store. Seems that is more the norm...

 

I have several troubleshooting steps that I came up with by analyzing the wiring diagram.

I will attempt these in the am.

 

Any other ideas?

Edited by xonix_digital
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Not the h4 relay kit is it? That could be the culprit right there.

 

 

My full ideas if you really need something to read...

 

Hmm just throwing out my train of thought, not trying to baby you or anything. It was working as intended when pulled apart, then you are unfortunately down to two main options. 

 

You plugged in something incorrectly or something failed.

 

The H4 has two filaments. I want to say the low beam shuts off when the high beam circuit is in play. 

 

A huge assumption here, not based on your intelligence, but because I am not there to inspect the wiring, let us assume that everything was plugged in in the correct orientation and focus on the failure points first.

 

So swapping the bulbs did not produce a change (just to verify, did it not produce a change as in the high beam was on, on one side, you swapped the bulb, and it was on on the same side?). That would say the bulb is out of the equation.

 

Next we can check the plug that feeds the bulb. If the bulb is working as intended the output is being fed incorrectly.

 

The plug has 3 prongs, one ground, and two power. I believe it should have 3 colors going to it, 2 of them being the same regardless of left/right orientation (one I imagine is black for ground, and the other is red/black for high beam).

 

The different one of the three (I believe one will be red, the other will be red yellow), will be the low beam.

 

So to summarize on the plug you have 3 prongs, on the driver side you will have a ground (black or brown), a low beam (red or red/white), and a high beam (red/black). On the passenger side you will have a ground (black or brown), a low beam (red or red/white the one not used on the driver side), and a high beam (red/black). 

 

Ground should have continuity to the chassis.

 

The low beam should read 12 volts when the low beam are on, and the high should read 12 volts when the high beam is on.

 

I am pretty sure you will find one of two situations. Your low will have voltage on the low only on one side, the other side will have voltage on the high. Or you will find the low will have voltage on one side, the other will have voltage on both the low and the high. Basically the info about the voltage to the prongs will really help us out. Also unplugging one side and plugging the other side in will also help. 

 

You can also check continuity between the the prongs, the left and the right low beams should be separate, and the high beams I imagine will be continuous to each other. The high beam and low beam should not be continuous with each side or on opposite side.

 

The above two pieces of information (where the voltage is going, and which prongs are continuous to what) will really help narrow down/shape what the assumptions are. 

 

Other then that you can trace it back and look at the fuse box (left and right have separate outputs) and trace it further back to the headlight/high beam selector. The contacts to the switches are open in that if they bend the wrong way a wire can easily short. And as mentioned the switches themselves are pretty cheap so it wouldn't be surprising if there is a cross contact (headlight wire running across high beam selector) or a broken/malfuncitoning switch.

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Sounds good, and update your damn blog, it's been ages!

 

Thanks SJ. I will update the blog soon. Just been focusing on getting this damn car up and running so I can enjoy it again.

Turned into the project that wouldn't end so I had to start banging things out.

 

So here's a fun development! First Z club meet of the year and the car is running great. Halfway home my dash lights go out on my four center gauges.

 

Take a look at the fuse box when I get back and this is what I see:

 

20150604_184643.jpg20150604_184926.jpg20150604_184824.jpg

 

Even without the fuse the two leads test 4ohms between one another.

Woops!

 

Gonna track the source of this down. Hopefully there isn't permanent damage to the harness beyond what I can see here.

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Success!

 

Ok so try and follow me here.

 

Here is my theory of the melted fuse box:

(Please correct me if my logic is flawed.)

 

The Flasher fuse melted above due to a faulty fuse.

The fuse was supposed to fail and break the circuit, but instead of blowing out the connection it sort of tried to turn into a light bulb. Meaning the fuse element did not blow out it just sort of melted causing a high resistance heat source. Replaced the fuse above and all of my dash gauges started working again as expected.

 

 

Back to the high beam issue:

 

After a few days of studying the wiring diagram and talking to everyone and their uncles about WTF. Noone has ever seen this issue before but everyone agrees that there is a short/ground issue in the high beam circuit.

 

My wife (of all people) was looking at the wiring diagram and said: "If you think you hooked all of this up right, then you are looking for something that is not on this diagram".. .lol EUREKA! 

 

I installed some LEDs to replace the indicator lights in the stock gauges (Directional signals, brake, and HIGH BEAM indicator lights). Turns out the High Beam indicator LED is in line with the actual high beam circuit and I installed it like an ass of jacks. Red lead to the RED/WHITE high beam circuit and black lead to the dash ground that I created for my gauges effectively grounding out the high beam circuit at all times. I also read that the high beam selector switch just changes which circuit is grounded (!) and not which circuit is getting power. That means that all I was doing my flicking the high beam switch is changing the path of least resistance hence changing which headlight's high beam element is illuminated (booyah).

 

Thoughts?

 

Shit is working. My passenger high beam isn't as bright as the driver so I'm not completely out of the weeds, but the indicator and high beams are operating properly enough.

 

I want to thank everyone that chimed in here. Even the little assumptions and facts that were brought up assisted in my overall understanding of the system, thus making it more and more obvious what and where I screwed up.

 

Thanks!

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