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[Datsun 1200 encyclopedia]

Headlight Wiring

From Datsun 1200 Club

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Category: Body Electrical System

Datsun B110 headlights are fused through the fuse box. No relays are used. Original Specs for headlights are 50/40 watt (standard large round headlights). From the fuse box "Battery" side (always hot, not dependent on ignition key position), through a 15-amp fuse the circuit goes to the Light Switch. From the Light Switch it goes to the Dimmer switch on the column. From here -- depending on the position of the Dimmer lever position -- it goes to either the low (DIM) beam of the headlights or the high (MAIN) beam of the headlights.

Also see: Headlight Specifications



The headlights are grounded via the main wiring harness.

Completing the headlight features is the "High Beam" light in the instrument panel. This is connected to the high-beam circuit to light up a visual indicator on the dash when the high beams are on.

So the headlight circuit has these components:

  • Two identical Headlights
    (Standard 12V "large round" type used by all makes of older vehicles)
  • 15A Fuse in Fuse Box
  • Light Switch
  • Dimmer Switch (T/S & Light Switch on steering column)
  • High-beam indicator lamp in instrument panel
  • Wiring and connectors
  • Relays are NOT used


The headlights are grounded via the main engine room wiring harness. The harness includes a body ground point (at the horn relay) and an engine ground (at the alternator E terminal).

23422.jpgAlbum 23422

Unlike some earlier Datsuns, the 1200 does not use a switchable earth in the headlight circuit.

Datsun 510 and early 620 use switchable ground. See 620 Headlight Wiring

Headlight Socket

Headlight socket
BGroundbody connection
RW(high beam) to one RW terminal of Dimmer Switchonly powered if Dimmer lever is forward
RB(low beam) to RB terminal of Dimmer switchonly powered if Dimmer lever is back

Light Switch

RHD and LHD use the same Lighting Switch with a 6-spade-connector. But for LHD applications the wiring harness only connects to four pins.

4-connector Headlight Switch is powered. The Fusebox feeds it

6-connector Headlight Switch is non-powered. The T/S switch inputs power to it.


6-connectors wired. Note that low beams will work in POS 1, while high beams only work in POS 2 (knob pulled all the way out).

10046.jpgAlbum 10046
With the knob pushed in, no circuits are connected.
With knob pulled out to Position one (POSH) you are simply smashing
With knob pulled out to Position two (POLL) you are just common
With knob TWISTED (Australia Only), the dash lights are bright or dim

Australia has an extra wire coming off the side of the switch (for a total of seven wires).


4-connectors wired up -- all Left-hand drive markets.

21187.jpgAlbum 21187
With the knob pushed in, no circuits are connected.
With knob pulled out to Position one, the parking lamps are activated
With knob pulled out to Position two, parking + headlights are activated

Position Connections
OFFno connections
Pull stop 1 (halfway out)
  • GL to GL (parking lights)
Pull stop 2 (all the way out)
  • GL to GL (parking lights)
  • R to R (headlights)

Light Switch connector
RHeadlight hot feed Input
  • from R wire of fuse box ('L' terminal)
RHeadlight circuit hot Output
  • To RY wire of Dimmer Switch
n/ano connection
n/ano connection
GLparking lights hot feed
  • from GL wire of fuse box ('PT' terminal)
GLparking lights circuit output
  • to GL wire of headlights
  • to GL wire of running (parking) lights
  • to GL wire of Instrument panel

Low/High Beam Circuit - 4-pole

For simple 4-connector light switch ONLY

21188.jpgAlbum 21188
With the T/S lever pulled back, power goes to Low beams
With the T/S lever pushed forward, power goes to High beams

Dimmer Switch (in T/S & Light Switch unit on steering column, only headlight section of switch listed here)
RYHeadlight hot feed
  • From R wire of Light Switch
RBheadlight low-beam
  • To RB wire of headlights
RWheadlight high-beam
  • To RW wire of headlights
  • To RY wire of "MB" light\* in Instrument panel
\* Labeled "Beam" for 1971. The other side of this light is grounded.

Low/High Beam Circuit - 6-pole

For 6-connector headlight switch ONLY.

Power from the Fuse Box Light circuit goes directly to the T/S switch. From there it is passed along to the Headlight switch and finally to the headlights. The headlight switch has seperate inputs for High and Low beams.

B:  earth/ground
RW: high beam
RB: low beam
RY: power input for T/S Switch
R: Lighting fuse

25097.jpgAlbum 25097

Passing Light Switch

A passing light feature was an option for B110.

See Main Article: Passing_Lamp


Datsun 1200 doesn't use a headlight relay, instead full power goes through the lighting switch and the dash harness. But a serious peformance issue is that the main wiring goes through a 20-gauge Fusible Link.

Headlights want a 14 gauge wire for the full voltage to reach the lights. If using high-power H4 lights, you might even go with yet even larger 12 gauge wire. There is no need to go any larger. The good news is that apparently Nissan already fitted 12-gauge wire! with 14-gauge for the low beams. So no need to replace the headlight sockets and wires, instead just add a relay to bypass the Fusible Link and feed in power through an extra Fuse.

Most cars use a headlight relay, to keep high power from going through the headlight and dimmer switches. You may add a relay to the Datsun 1200 to improve the power to the headlights. Some club members report the headlights are much brighter when wired up this way.

14978.jpgAlbum 14978

You can get 14-gauge connectors and wires, the fuses and lengths of wire from a wrecking yard. Or buy the parts new, which is easier.

POST Discussion

POST relay kit less expensive than used parts
174_5d0c702f1311a.jpgPost 491750

Harness Kit

If you have more money than time, a Relay wiring kit is really easy:

Take the new harness:

  1. Connect HOT wire
  2. Ground/earth the relays
  3. Plug into existing headlight connector
  4. Plug harness into headlights
  5. Comes with the proper fuses and will bypass the stock Fusible Link

You're Done! Only $129 USD Painless Wiring Headlight Harness with relays


Do it yourself. I recommend 14-gauge wire for Halogen, but you can use 12-gauge wire for H4 high-power headlights. 14-gauge can handle 24-32 amps for 10 foot (3 meter) length, which is plenty as Halogen H6204 high beams (two bulbs) draw only 12 amp maximum at 15V. The extra capacity will keep the voltage drop minimal. If the length of + and - wire is 10 ft total, expect 12A draw voltage drop to be 0.6V at 12V with 14 gauge wire and 0.4v with 12 gauge wire.

  • 14-gauge wire for the HOT side (RED or whatever color you want)
  • 14-gauge wire BLACK for the earth/ground side
  • Headlight connectors with 14-gauge leads
  • Two fuses (or circuit breakers?):
    • 15 amp for high beam Halogen 65W bulb x2 (up to 150W total)
    • 20 amp for H4s (up to 200W total)
    • 10amp for low beam (up to 100W per side)
  • Two relays of 20A minimum rating, get a reliable OEM unit like this common Nissan part:
    21854.jpgAlbum click to view
  1. Connect two short lengths of red wires to the BAT + or ALT + (your choice)
  2. Fix fuses to these two short HOT wires, to protect the rest of the new wiring
  3. Then more HOT to the Relays (D). Keep the wires as short as is feasible
  4. more HOT wire from relays to the headlight connectors
    22113.jpgAlbum click to view
    • High-beam relay (B) to the new headlight connector 56a High-beam
    • Low-beam relay (B) to the new headlight connector 56b Low-beam
  5. Fix BLACK from new headlight connectors to a body ground or engine block
  6. Fix BLACK from Battery cable terminal to body ground (not needed if your Battery cable is already 12-gauge)
  7. connect small wires (20 gauge is fine) from one of the original headlight connectors to relays. Just leave the other connector alone.
    • One wire from 56b to the low-beam relay switch trigger (C)
    • another wire from 56a to the high-beam relay switch trigger (C)
  8. connect small black wire to ground both relays switch (E)
    can ground it:
    • to body, or
    • to engine block, or
    • or to 31 of original headlight connector
  9. To prevent corrosion, seal all the wire connection ends with a sealer (shrink-wrap) 

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