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PKD

Headlight Gremlins

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My 1976 280Z headlights won't  turn on. We had the dash out to work out some other issues when we put it all back, the running lights work, as the turn signals, but there is no headlights. Checked the switch with multimeter and have full voltage at all wires when lights are turned on. The voltage turns off when off. No problems there. High beams don't work either. Checked voltage at high bean wire input at switch and only get 3.5 volts. Checked at Relay, the direct power is at 12+ but the input wire was also at 3.5volts for both high and lows. What did I disconnect or not reconnected properly under dash that could cause this?? They worked shortly after a drive around the block but stopped working the next time we went out for a ride!! Going nuts trying to find problem. Even changed the relays but no change. Checked under grill, pulled the connectors to left and right headlight and had no voltage at front of car. So the problem lies between the switch and the relay. Any ideas?  Has this happened to anyone else that pulled the dash?? What connectors should I check?? I checked everything at the steering wheel.

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Did you check the dimmer switch?  At the base of the turn signal.  It's a common cause of "no headlights".  It's the ground point for the lights.

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20 minutes ago, Zed Head said:

Did you check the dimmer switch?  At the base of the turn signal.  It's a common cause of "no headlights".  It's the ground point for the lights.

How would I go about checking it? I did turn the knob all the way up then down, but to no effect. Does it short out the lights? Is it a wire that hooks up somewhere under the dash or to the light switch?

 

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Go to the downloads section on this site and get the factory service manual for the 76. There's a link in my signature (provided you're a luddite like me using a computer instead of a smart phone).

Once you have a copy of the FSM, go to page BE-11. It gives a breakout of the headlight circuit.

Instead of measuring random wires, target the circuit. For instance, do you have 12 VDC to ground at each of the headlight fuses when the switch is on?

Also, there is not a relay in the factory wiring for the headlights. Where is it located? What factory wires are connected to it? Is there only 1 relay? Normally there would be 2 for the headlights. 

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41 minutes ago, PKD said:

How would I go about checking it? I did turn the knob all the way up then down, but to no effect. Does it short out the lights? Is it a wire that hooks up somewhere under the dash or to the light switch?

Steve makes good points.  The wiring diagram in the Body Electrical chapter of the FSM is your best bet.  It shows a little drawing of the dimmer I think as part of the schematic.  And, as he says, there is no relay.  Just wires to the switch then the fuse box, the lights, the dimer, etc.  So that needs figuring.  

Pretty sure that there's a separate specific wire with its own connector for thew ground (not a short) of the headlights.  It would be shown in the schematic.  Maybe it worked loose.

No offense, but you'll have to get up on your electrics terminology.  A "short" mans the electricity got away from the path it was supposed to follow.  Took a short cut.  It's all about proper paths, making the electricity work.

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2 minutes ago, SteveJ said:

Also, there is not a relay in the factory wiring for the headlights. Where is it located? What factory wires are connected to it? Is there only 1 relay? Normally there would be 2 for the headlights. 

Nope, not much OEM in this little beastie! The previous owner wanted a track car he could drive to the track. . . pretty unsuccessful due to all what he ripped out. I am re-hooking as I go. The headlights are a little more modern so it required new relays. He took a late model box and installed it in the engine compartment. There are two relays as you supposed. The engine out of a 82 is completely rebuilt with the turbo in mind. The ecm is mega squirt, in which I am trying to interface with given it runs so rich i gag on the carbon monoxide at every light or stop sign.  The drop in power on the input is definitely under dash somewhere between the switch and relay. If the voltage is dropped, would that not indicate some sort of short or reduction of voltage through bad connection?

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5 minutes ago, Zed Head said:

The path.  it's all about the path...

Yep, thus the question, what could lower voltage between switch and lights. How would the dimmer effect this? Checking the resource Steve mentioned as we speak.

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2 hours ago, PKD said:

How would I go about checking it? I did turn the knob all the way up then down, but to no effect. Does it short out the lights? Is it a wire that hooks up somewhere under the dash or to the light switch?

 

I think that he meant the low/high beam switch on the blinker stalk, not the dash light dimmer knob.

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2 hours ago, Zed Head said:

Did you check the dimmer switch?  At the base of the turn signal.  It's a common cause of "no headlights".  It's the ground point for the lights.

 

15 minutes ago, w3wilkes said:

I think that he meant the low/high beam switch on the blinker stalk, not the dash light dimmer knob.

Ding ding ding, guess its getting too late for me to comprehend that the reference of "dimmer switch" had another meaning other then a rheostat. I went crazy looking at the path and seeing no correlation between the two circuits. . . duh. OK, to answer that question Zed, yes, that is where I saw the 3.5 volts that followed to the relay with the same results in voltage. This hi/low switch, does it foul(IE needing cleaning) or is it broken and requires replacement? Voltage leading to it is definately 12+volts, going to the head lights is 3.5volts. Path confirmed. Finally, any clue who would have a replacement of this switch, affordably,  if not repairable??

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It's a switch.  100% to one path, or 100% to another.  They get dirty.  You can take them apart and clean them or just squirt contact cleaner in and work the contacts.

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I started a topic not long ago in "electrical" where I upgraded the headlights and added a relay harness to my 280z.  Great upgrade, check it out.  Pretty simple and inexpensive too, to prevent further headlight problems. 

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My lights went out a couple of months ago after I clicked the dimmer switch. Ended up opening up the the switch mechanism and cleaning everything.... once I put it back together they worked great. Just a dirty connection.

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1 hour ago, Dogariffic said:

My lights went out a couple of months ago after I clicked the dimmer switch. Ended up opening up the the switch mechanism and cleaning everything.... once I put it back together they worked great. Just a dirty connection.

These Z cars (and most cars) route the 12V through the headlight system, which is not only inefficient, but wears the contacts of the switches.  That is why I highly recommend the relay/harness upgrade.   You can still use your sealed beams (switch the connector terminals if needed).  The voltage comes directly from the battery.  

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I have completed my fight with the headlight gremlins! I had followed the path up down, side to side, and into several conclusions that lead to. . . basically nowhere.

 

Checked the circuit from light switch and found everything correct. Proper voltage, on/off circuit properly working. Checked and cleaned the hi/low beam switch or better referred to as a 'dimmer switch'.

 

As I checked the continuity of the dimmer switch with the multi-meter, I discovered the switch works fine. When attached to the under-dash wire, both hi and low circuit show return instead of hi or low. Thus a short is apparent. I checked the path with the map to discover a probable cause.

Being the wiring has been disturbed for the upgrades to a more modern fuel injection system, as well as modern headlight system, relays were added. I then checked these relays to figure out if there was any disconnected or crossed wires. All functioned well. Then to the headlight loom. No problems there, other then no voltage at all. It had to be under dash, since that was where the problems began after a new speedo cable was installed. It turns out that the tachometer was rebuilt to connect to the new ecm. I had taken it apart to check as to why it would not interact with the ecm to discover the potentiometer was broken. The wiring had loose fitting. Regardless to say, the previous owner had not assembled it correctly. I went back to this and found a wire making ground contact with the dash frame that caused a short in the ground circuit that was in circuit with the dimmer switch. Lights on!

 

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@PKD

You need to start a thread for your car and show us what's been done. Looks fairly heavily modified: turbo, manifold, fuel rail, intercooler, etc.

We like pics :P because some of us don't read so well. By the way if you're ever in the upstate PM me and you can swing by the house...

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11 hours ago, Patcon said:

@PKD

You need to start a thread for your car and show us what's been done. Looks fairly heavily modified: turbo, manifold, fuel rail, intercooler, etc.

We like pics :P because some of us don't read so well. By the way if you're ever in the upstate PM me and you can swing by the house...

Yes Patcon, I would love to start a thread. There is so many things done to this Z. I would have to find the spec sheet I received from the former owner. The engine was well built and runs well. Awesome power. Just need to get into the Megasquirt program to get the rich fuel mix to a more normal, less fume ridden mix. That car will make your eyes tear at stop lights. The former left it this way because he wanted to break it in without overheating. Since then I have added the charcoal canister back on to cut back the fumes from the tank. Why folks think removing this is a good idea, I don't know. He also disconnected the entire wiper system, I reinstalled. He took out the air system, which I have in boxes, I intend to reinstall. No heat, no vacuum line or canister to operate it. The suspension needs to be soften just a little so pot holes and speedbumps don't do damage to my spine and to the car's. Steering is wonky at best. Passenger front steering bolts came loose, had to tighten the whole rack up, needs alignment, still wobbly at highway speed. Leaking passenger door above window. And last but not least, the rear clunks like crazy! So many things can be wrong down there. Would like to convert the diff to a LSD so she isn't pegleg anymore!

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Find that build sheet and do it. I am sure the forum can help with many of those issues

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7 hours ago, Patcon said:

Find that build sheet and do it. I am sure the forum can help with many of those issues

Will do!

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