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Revision as of 09:00, 1 March 2013

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 Headlight Socket
4 Light Switch
- 4.1 RHD
- 4.2 USA
5 Low/High Beam Circuit - 4-pole
6 Low/High Beam Circuit - 6-pole
7 Passing Light Switch
8 Relay
- 8.1 Harness Kit
- 8.2 DIY

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

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

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

Light Switch

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.

RHD

6-connector Headlight Switch.

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 (for a total of seven wires).

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 - 4-pole

For simple 4-connector light switch ONLY

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.

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

Diagram

Passing Light Switch

A passing light feature was an option for B110.

See main article: Passing Lamp

Relay

Datsun 1200 doesn't use a headlight relay. But a more serious peformance issue is that the main wiring goes through a 20-gauge Fusible Link.

Headlights want a 14 gauge wire -- much larger than 20 gauge -- 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 14-gauge wire, with 12 gauge for the high beams! So no need to replace the headlighgt sockets and wires, 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.

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.

Discussion

Harness Kit

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

Take the new harness:

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

Your'e Done! Only $129 USD Painless Wiring Headlight Harness with relays

DIY

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:

Connect two short lengths of red wires to the BAT + or ALT + (your choice)
Fix fuses to these two short HOT wires, to protect the rest of the new wiring
Then more HOT to the Relays (D). Keep the wires as short as is feasible
more HOT wire from relays to the headlight connectors
- High-beam relay (B) to the new headlight connector 56a High-beam
- Low-beam relay (B) to the new headlight connector 56b Low-beam
Fix BLACK from new headlight connectors to a body ground or engine block
Fix BLACK from Battery cable terminal to body ground (not needed if your Battery cable is already 12-gauge)
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)
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
To prevent corrosion, seal all the wire connection ends with a sealer

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Headlight Wiring