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Discussion Starter · #1 ·
my passenger side low-beam will not come on. i have a '78 280. the high beam works and i have checked the bulb, changed headlights for known good unit, cleaned the connectors at the socket and the links under the 2 plastic covers. it seems like i have 12v to all 3 plugs on the socket. what have i missed?

Tim 78 280z
 

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> my passenger side low-beam will not come on.
> i have a '78 280. the high beam works and i
> have checked the bulb, changed headlights
> for known good unit, cleaned the connectors
> at the socket and the links under the 2
> plastic covers. it seems like i have 12v to
> all 3 plugs on the socket. what have i
> missed?

i have a 78 280z that used to do the exact same thing. i can only tell from experience what i did and that was to mess around with the switch and clean all the connections that could possibly deal with electricity until it worked again, however if you have already done this then i don't know what else to say.
 

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TIM 78 280Z
TRY CHECKING YOUR CONTACT POINTS IN YOUR HEADLIGHT SWITCH OR MAKE SURE THAT YOUR GROUND WIRE IS CLEAN AND GROUNED GOOD.
YOU MAY WANT TO GET ANOTHER HEADLIGHT SWITCH FROM A WRECKING YARD AND PLUG IT IN AND SEE IF THAT FIXED YOUR PROBLEM.
IF YOU NEED MORE INFOMATION FEEL FREE TO DROP ME A LINE.

MD MIZE
 

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Here's how I read the schematic:
Power is split for the left and right bulbs at the fuse box, hence the left and right headlight fuses. These power lines run to the common terminal in the headlights. Then by selectively grounding the other pins, high or low beams are turned on. Left and Right Low Beam Pins are tied together and brought to the switch, as well as both High Beam Pins.

So to me, all this means that if you must have a break in the right low beam wire, before it joins with left low beam wire. Otherwise the right bulb wouldn't work at all, or both low beams wouldn't work. I suggest checking again the connector for corrosion, and finding the point at which the low beam wire splits in the harness.

> my passenger side low-beam will not come on.
> i have a '78 280. the high beam works and i
> have checked the bulb, changed headlights
> for known good unit, cleaned the connectors
> at the socket and the links under the 2
> plastic covers. it seems like i have 12v to
> all 3 plugs on the socket. what have i
> missed?

> Tim 78 280z
 

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> Here's how I read the schematic:
> Power is split for the left and right bulbs
> at the fuse box, hence the left and right
> headlight fuses. These power lines run to
> the common terminal in the headlights. Then
> by selectively grounding the other pins,
> high or low beams are turned on. Left and
> Right Low Beam Pins are tied together and
> brought to the switch, as well as both High
> Beam Pins.

> So to me, all this means that if you must
> have a break in the right low beam wire,
> before it joins with left low beam wire.
> Otherwise the right bulb wouldn't work at
> all, or both low beams wouldn't work. I
> suggest checking again the connector for
> corrosion, and finding the point at which
> the low beam wire splits in the harness.

I had the same problem , but on the drivers side. Took it to a mechanic and it turned out to be a short on the wire after the split at the harness. He had to trace the line out and repair the wire.
 

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Discussion Starter · #6 ·
Re: question for Larry

> I had the same problem , but on the drivers
> side. Took it to a mechanic and it turned
> out to be a short on the wire after the
> split at the harness. He had to trace the
> line out and repair the wire.

where is the split in the harness? right behind the radiator support?
 

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Re: question for Larry

> where is the split in the harness? right
> behind the radiator support?

The split is right in front of the radiator, the ground or short occured as the wires enter into the headlight bonnet area.
 

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Discussion Starter · #8 ·
Re: another success story!!

> The split is right in front of the radiator,
> the ground or short occured as the wires
> enter into the headlight bonnet area.

thanks, Larry!! also thanks to MattW, MDMIZE, and ConorP, you all helped solve the problem!! the plug just inside the fender well before the bonnet is a shielded connection but corrosion still managed to find the male pin on that side. i sanded the rust off, applied some di-electric grease, and it fired right up. many thanks again to everyone)
 
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