Basic Alternator Wiring

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There are three basic type of Datsun alternator, each with their own wiring system.

• 1960s Datsun Alternator (4-pin rectangular connector)
• 1970s Datsun Alternator (2-pin T-connector with external Regulator)
• 1980s Datsun Alternator (2-pin T-connector with Internal Regulator)

1960s Alternator

Datsun 1000 Type (LT125 Hitachi)

From the introduction of the Datsun with alternator (circa 1966), it used a Hitachi type with a 4-spade rectangular connector. As usual with Datsun there equivalent Mitsubishi-sourced versions too. This type was used by Datsun 1000, Datsun 411 and early Datsun 510, among others.

Large Wires 
* A to Fusible Link on positive battery cable (White wire)
* E to earthing point (Black wire to engine block)

Four-spade rectangular connector
(Datsun 1000 colors)
WB - to Regulator WB (12V always)
W - to Regulator W 12V IGN 
Y - to Regulator Y (nuetral wire for lamp relay)
B - to Regulator B (earth/ground)

1970s Alternator

FN type

From about 1970-1978 (in USA market), Hitachi type LT alternators were used. There were also equivalent Mitsubishi units which are interchangeable. These feature the famous 2-pin T-connector with external Regulator. Datsun 1200 used this type, as did other 1970s Datsuns.

These use FN wiring. They have F and N cast into the back cover. An external Voltage regulator is required.

See main article: Alternator Wiring

NOTE: LT135 35A units have black plastic bits. The larger LT150 50A and LT160 60A units have no plastic parts

These are marked FN on the back. However, it is common with rebuilt units to have their cases sand-blasted, in which case the letters are often unreadable.

1980s Alternator

LS type

From about 1979 (in USA market), Hitachi type LR alternators were used. There were also equivalent Mitsubishi units which are interchangeable. These feature the famous 2-pin T-connector BUT use no external Regulator. They are internally regulated, which makes them more reliable as they use an IC (solid state) regulator.

This type was also used by 1989-1994 1200s.

These use LS wiring. Some has L and S cast into the back cover, but some are unmarked.

See main article: Hitachi_LR_Alternator#Wiring

Mixing and Matching

It is possible to use a different type alternator in your Datsun than what it was designed for. But you need to make slight modification to the wiring.

IR Alternator In Older Datsun

This is very do-able. Hitachi IR alternators are more reliable and sometimes less expensive.

Datsun With FN Harness

Fitting an internally-regulated alternator to a Datsun originally equipped with FN wiring is quite simple. It only requires two jumper wires.

For detailed information, see Hitachi_LR_Alternator#Wiring

Datsun With 4-pin Harness

Wiring up an internally-regulated alternator to a Datsun originally equipped with FN wiring is fairly simple. It only requires four jumper wires. Note that physical mounting of the alternator is not discussed here (it may not actually bolt to the engine).

1. Disconnect Regulator
2. In the engine-side harness for the regulator connector:
   * Jump W to Y wires 
   * Jump WR to WB wires 
3. In the engine harness at the alternator (4-pin connector)
   * WB wire - jumper to alternator's T-connector stem
   * Y wire - jumper to alternator's T-connect head

CAUTION: Make sure the A and E wires from the back of the alternator are of enough gauge for the current produced by the new alternator.

It is recommended that you obtain a female T-connector and solder it to a female 4-pin connector to make a custom alternator adapter-connector, so it can only be inserted one way by mechanics and future owners.

Older Alternator in Newer Datsun

For Datsuns originally fitted with internally-regulated alternators, it is not recommended to adapt an older alternator, as the newer alternators are generally less expensive, more readily available and more reliable.

4-pin Alternator in FN Datsun

This requires for jumper wires in the 4-pin rectangular connector:

1 B wire - jumper to alternator E terminal
2 W wire - jumper to alternator A/BAT terminal
3 WB wire - jumper to T-connector stem
4 Y wire - jumper to T-connect head

Question: Is the newer regulator compatible?

NOTE: Do not substitute a 25A unit where a 35A unit belongs. 35A amps is enough for headlights, wiper and heater fan simultaneously running, but 25A is not enough for all combined.

FN Alternator in LS Datsun

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SYMPTOM: Alternator overcharges big-time! Battery overflows and makes fumes.

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If your Datsun came with I/R alternator, and you simply replace it with an externally regulated alternator, it will be stuck ON and overcharge!

To make this work, you will need to create a sub-harness with wiring for an external voltage regulator. New Voltage Regulators in USA generally cost more than an internally-regulated Alternator!

TBD - request a writeup