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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

1 Overview
2 Earthing
3 Light Switch
4 Australia
- 4.1 USA
5 Low/High Beam Circuit
6 Headlight Socket
7 Passing Light Switch
8 Relay
- 8.1 Harness Kit

Overview

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

Earthing

The headlights are grounded via the main wiring harness.

Light Switch

Australia

light switch - Australia

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, the dash lights are bright or dim

USA

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

OFF	no 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

R	Headlight hot feed Input from R wire of fuse box ('L' terminal)
R	Headlight circuit hot Output To RY wire of Dimmer Switch
n/a	no connection
n/a	no connection
GL	parking lights hot feed from GL wire of fuse box ('PT' terminal)
GL	parking 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

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)

RY	Headlight hot feed	From R wire of Light Switch
RB	headlight low-beam	To RB wire of headlights
RW	headlight 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.

Headlight Socket

Headlight socket

B	Ground	body connection
RW	(high beam) to one RW terminal of Dimmer Switch	only powered if Dimmer lever is forward
RB	(low beam) to RB terminal of Dimmer switch	only powered if Dimmer lever is back

Passing Light Switch

A passing light feature was an option for B110. If your turn-signal lever has a push-button on the end, it's the passing light switch. Push it in, and the headlights light while it's pushed in (regardless of whether lights are on or off).

This is composed of two parts:

The switch itself is part of the turn signal (on the steering column).
The relay. 1200s don't use headlight relays, except for this optional Passing Switch. It looks very much like the Horn Relay.
- 25230-89912 RELAY-passing lamp (4-connector relay on early models)
- 25230-89905 RELAY-passing lamp (3-connector relay from 1971 Apr)
- 26320-14800 RELAY-horn (has 3 connectors, located by Coil)

Note that this just wires in series with the standard wiring. From the 'L' fuse to the high-beam wiring, the switch bypasses simply the regular switch, firing the Main Beams.

Passing Light Switch circuit

The red circle indicates the part of the T/S switch that is different from a normal T/S switch

Relay

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.