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620 headlights wont work


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I went to go take the truck out, and my headlights wont turn on.

The parking lights work, but when i pull the lights switch all the way out to headlights, nothing happens.

I checked the fuses and none look burnt out.

There is a wire hanging free that I didnt notice before.

Its a thick red wire spliced onto a thin brown wire that I traced back to the wiper switch.


I dont know much about electrical systems, so Im stumped.

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Thanks for the quick reply!


Yeah that Red wire should be connected to the front right hand 15 amp fuse.


I am here in the truck now. There are 2 rows of 3 fuses.

I assumed you mean the top right hand fuse.

In the back of the fuse box, there is a white plug going into the box with a green wire on top, and a hole on the bottom.

I stuffed that red wire into the hole and tried again, but nothing.


What am I doing wrong?

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Turn on the headlight switch and wiggle your turn signal lever. If the headlights come on, something is loose or damaged in the T/S-high beam switch.



Generally to solve this problem is not a matter of "try this, try that", but involves carefully tracing the circuits until the problem is found.


I could come by and look at it with you. I'll PM you my phone number.

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i have the same problem, but my high beams work but my lowbeams dont work. wtf!!!!!!!


If all four headlights are ON and if it's your '74, (you don't say) there is a headlight relay on the rad support between the battery and rad I think. Give it a good smack. If that does not work find some way to disconnect the Red/White wire from the relay. This will disconnect the high beams but leave the low beams on.

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Here is the early 620 fuse box:



(same as Datsun 1200).


The thick red wire goes on the underside of the box, to the 20A section.




Ok, this helps so much!

I was pluging the wire into the parking/ tail light side, so no wonder it didnt work.

Im going to go back out there in the morning and try again.


Thank you ggzilla and datzenmike for taking the time to help me out.

This community is the best!

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So just an update.


I was able to get the lights working again by running a wire off the switch, to the fuse box.

The red wire I mentioned before was all wrong. It was randomly spliced into an unidentifiable wire somehow mated to the washer switch. Oh, and it was just twisted, not even taped up. Scary.


Of course during the battle, I somehow disabled my gas gauge and turn signals.

*palm to forehead*

At least I got home safely.


Thanks again to datzenmike for lending expertise, and to ggzilla who talked me through the procedure and didnt get too frustrated with me.

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  • 13 years later...

hi i have a 1976 datsun 620 im having problems with my wires for my lights so i have new back tail lights hooked up which i have unplugged at main point and have also unplugged under the passenger seat    now my problem is when i turn on the lights all for head lights turn on low and high beam i have changed the switch and i have tried other signal switches as well and also different flashers and have no side maker light as they have bin deleted i have changed all the fusses i have tried other relays as well when its all plunged back in i have still the 4 lights on the front marker lights both stay solid  and the back light have no signal or brakes the revers lights work tho so im asking for some help is there something missing or is there like a relay not working or even one missing    no i have also had all these light working before a year ago and the only thing that i have changed wire wise id i used the factory power to power up a after market deck witch i have unplugged and still does same thing  still need help please i just want to drive this truck after 6 years of redoing it 

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Justin, please use some periods and capitals. I have no idea what you are trying to say as your sentences run-on with no end or beginning to them. I can only guess as to what you trying to say. Guessing is no good.



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If reverse lights work the ground is also working.


Are the dash lights working? I assume they are. There is the 10 pin plug under passenger seat. Get a $5 test lamp and find the Green/Blue stripe wire and test for power with the headlights ON. This is the side marker, running lights and the license light. If power go to the right (passenger) side tail light. Behind it near the end of the frame there is a round 6 pin plastic plug that joins the frame harness from the cab to the tail light harness across the rear. Unplug and again check the Green/Blue wire for power.


No power.... there is a break in the harness between here and the 10 pin connector under the seat. Look for a poorly done trailer splice or rock damage on this harness.


Yes there is power.... connect up the plug. Sometimes the act of unplugging and plugging in will re seat the connection. If nothing the problem is in the harness across the back of the truck. Again look for an attempt by a previous owner to to install a plug for towing a trailer. These are never done right and water gets in and corrodes the copper wires. 


Do you have license plate light??????

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Thanks you 

So what about the front when I pull the head light on the high beam and low beam are on and the front signal lights are soild . And when I try to turn of and on the high beam nothing changes and the signal light don't work either. I have tryed different flasher as well nothing.all fusses are new as well .for the side maker light I do not have them at all becouse I shaved them gone .

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On 7/13/2023 at 11:04 AM, datzenmike said:

If reverse lights work the ground is also working.


There is the 10 pin plug under passenger seat. Get a $5 test lamp and find the Green/Blue stripe wire and test for power with the headlights ON.



What happens???????? This will determine what to do next. Get the rear running light and flashers working and it might fix the fronts.

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