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Revision as of 07:16, 19 November 2012

Our Datsun B110 used -- as with most 1964-1974 cars -- an Alternator with external Voltage regulator.

1 Overview
2 How the Alternator Dash Light Works
3 Automatic Choke Relay
4 Late-model Alternator

Overview

Alternator Connections

terminal	Color	Logical Connections
A (Alternator)	WR or W	* To Battery + terminal through the Fusible Link * To Regulator "A" terminal (W wire)
F (Field)	WB	* To Regulator "F" terminal
N (neutral point)	Y	* To Regulator "N" terminal * To electric choke relay Y wire
E (Earth/ground)	B	* To body ground * To Regulator "E" terminal

Regulator Connections

terminal	Color	Logical Connections
A (Alternator)	W	* To Alternator "A" terminal (WR or W)
F (Field)	WB	* To Alternator "F" terminal
N (nuetral point)	Y	* To Alternator "N" terminal * To electric choke relay Y wire
E (Earth)	B	* To body ground * To Alternator "E" terminal
IG (ignition)	WL (72: W?)	* To fuse box "M" terminal (does not go through IGN switch)
L (Light)	WR	* To dash light "IGN" ('72, '73) or "CHG" (1971)

Hitachi LT-series uses the typical 1970s Hitachi T-shaped connector:

F Field - stem of Tee
N Nuetral point - head of Tee

How the Alternator Dash Light Works

The dash lamp is connected to IGN +. The other side goes to the "L" terminal of the external regulator.

When the alternator is not putting out current, the "L" terminal is at '-' voltage, so the dash light turns on
Once the alternator starts putting out current, the "L" terminal is at + voltage, so the light turns off (both sides of the light are at +)

This also is connected to the F (field) connection of the alternator, so it "turns on" the alternator. It is the switched 12V (through the lamp) that kick starts the alternator fields.

WARNING: This mean that if the dash lamp 
is burned out, the alternator does not work

Automatic Choke Relay

On Datsuns equipped with an electric Automatic Choke, a relay is used so that the choke heater is activated only when the engine is running. It uses a normally connected relay -- the choke is powered all the time when IGN is on, but when the engine is not running the relay disconnects the choke power.

As soon as the choke heater gets hot, it comes off the choke. If your engine is cold, you won't be able to restart it. For example, if you listen to the radio for a couple of minutes before starting the engine, and mistakenly put it to IGN, then the car won't start on a cold day. To prevent this scenario, the relay only powers the choke when the engine is running. The alternator provides a signal when the engine is running. It is the Neutral Sense wire (N wire). This is a weak signal so a relay is used.

B110 Choke Wiring

The 1972-1973 auto choke is powered by a separate 10A fuse. On a 1973 this also supplies the Anti-diesel valve.

The power side of the relay normally connects the IGN wire to the choke wire.

L (Blue): to 10A fuse then to IGN switch
Red: choke

The relay is activated by these two wires:

Black: ground
Yellow: N wire of alternator & regulator (turns on relay)

The factory 1200 auto choke setup (1972 & 1973 USA models) uses a relay:

Red - to choke
Yellow - to "N" wire of regulator/alternator
Blue (L) - to Fuse 10A in fuse box IGN side
(also to Anti-diesel valve on 1973 carburetor)
Black - to ground/earth

Location of Choke relay: To left of radiator

Simple Wiring

For cars without a choke relay, you can simply hook the choke up to the Hot side of the ballast resistor -- it seems to work fine. The only downside I've observed is when you can't get the engine started right away, the choke heats up while you are trying - on cold days you may never get it started. So using the alternator output and a relay is a better idea.

Part Numbers

25235-P0101 ASSY-RELAY,HEATER,AUTO CHOKE $68.68
superseded 25235-P0100 ASSY-RELAY,HEATER,AUTO CHOKE 0671- USA
* Same as Datsun 510
* Same as Datsun 521 pickup
* Same as 1974 Datsun 710 
* 25235-P0110 NILES brand
240Z Pump Relay
* F.D Furuhashi/Elecman SRK12-1
* Beck/Arnley 203-0015

4-pin spade connectors, Normally Open

Alternatives

The B310 relay is much cheaper, but has six connectors. 2 would remain unused if you used that switch which has a different connector. 25230-89915. This assumes that is has NO and NC connections. Use the NO connections to replace a B110 relay (not confirmed if this will work)
B210 relay is similar, but uses B210 style (round) connector 25235-H6200/B5235-H6200
Generic 12V normally-open Relay could be used

B210 Choke Wiring

B210 with IR (1978) uses 6 connections wired oppositely to prior type (not shown)

1974 B210 North America uses 4-pin round connector.

Below: 1976 North America B210 uses 6-pin relay (one pin is Not Connected) with semi-rectangular connector.

photo

Choke Wiring is logically same as B110, except that the Brake indicator lamps are also controlled by the dual-pupose relay.

B310 Choke Wiring

B310 uses a combo relay, six connectors with both normally open and normally closed pairs. Turning on the ignition switch activates the relay, pulling power away from the choke heater. When the engine starts, the relay turns off, resuming flow of power to the choke.

NA B310 uses internally-regulated Hitachi LR Alternator with L terminal in place of N terminal.

The relay controls

Normally Closed (de-activated when relay is ON):
- Choke Heater
- Fan relay
- Warm-up Relay 1
Normally Open (activated when relay is ON:
- Brake lamps

Locations

The choke relay is mounted in the relay box on the rigth side strut tower.
The check test connector is located under the dash near the fuse box.

25230-89915 RELAY ASSY-AUTO CHOKE $24.57 USD
B5230-89985
240Z ignition relay

6-pin spade connectors, Normally Connected + Normally Open

Late-model Alternator

Datsun 1200 from 1981 (Japan-market models) use an alternator with internal regulator.

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Alternator Wiring