Headlight Relays and Wiring Harness (180B)

[Bluebird_U]

Hi, just one for the elec-trickery able people out there. Please feel free to point out any faults, errors, things that could/ needs to be done better/ different so that other can learn from what I usually do.

Now the back story, as being stuck in/ near the house it seems a perfect time to avoid any actual work and instead work on Datsun things that are of benefit – in this case see if relay harness I have improves the lighting, and takes the load off the steering column switch, which given the age and that they take the full voltage to the lights could fail. I had in the long past purchased a 4 light harness and relay of our good friend dodgy Alli.
https://www.aliexpress.com/item/3274905 ... 37559%2326

Now comes the time that I move some s**t in the garage to keep busy and find the harness and think, there are probably more constructive things to do – so i’ll do this instead.

After removing the grill and lights (for extra cleaning tidying up work of course) I lay out the harness, connect the red fused line to the battery, the black plug to the high/ low plug on the body harness (drivers side), the high and low plugs to the lights and the black wires to bolts on the body. Well that went well, everything clips together and looks ok – now to see if I can make smoke from electricity like usual....
And thanks for reading this far – now the exciting part.
Connect up the battery - no smoke, ignition to on - no smoke, turn lights on - no smoke, and the two outer bulbs light up – scratch head and think “it cant be that simple”, and you'd be right.

When switching to high beam the high/ low (drivers side) goes super bright, the high (drivers side) goes bright while the high and high/ low (passenger side) are both the same dull... and still no smoke.
While obviously half them are now brighter are its not something that would pass a WOF eventually so I need some help figuring out where things have gone wrong (its usually the I d 10 t issue).

Now for the technical part;
Relay 1 – (Cross shape with wire in the middle)
87
86 87A 85
30
Red wire – Pin 30/ 80 (cant see full number as there sealant over part) from the battery to relay
Smaller blue wire (1x) – Pin 85, (connection to existing harness)
Thicker blue wires (2x) – Pin 87, (connect to blue light plugs)
Smaller blue and black wires (2x) – Pin 86, (blue to second relay – Pin 85, black to existing harness)
Thicker blue wire (1x) – Pin 87A, (to second relay – Pin 30)

Relay 2 – (Cross shape with no wire in the middle)
87
86 85
30
Thicker blue wire (1x) – Pin 30(only input wire from Pin 87A Relay 1)
Smaller blue wire (1x) – Pin 85, (only input wire from Pin 86 Relay 1)
Thicker white wires (2x) – Pin 87, (connect to blue light plugs)
Smaller white wire (1x) – Pin 86, (connection to existing harness)

So my thinking at the moment is the harness is probably positively switched where as most Datsun / Japanese cars are negatively switched and therefore the wiring needs to be changed around, similar to the second diagram in this site https://www.danielsternlighting.com/tec ... elays.html.

Anyone have any ideas, or should I;
• just follow the diagram and put in two power supplies and two 4 pin relays, or
• does anyone have a better diagram with wiring layout

Thank you for your time, and hopefully I have also provided some entertainment.

[Otodat]

I would personally pull the earths of and check them, or run a jumper cable to each side from the battery negative. The loom itself looks ok to me at a glance. If one side switches high to low i would think the harness itself was ok. If you have a tester or volt meter you could disconnect the plugs from the headlights and verify each wire is powering up.

[Bluebird_U]

Thanks for the advise. I chucked the jumper cable between the negative wires on the loom and the battery and they all light up evenly between both sides on high and low beam, so it looks like a dodgy earth connection on my part.