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[Datsun 1200 encyclopedia]

Voltage regulator

From Datsun 1200 Club

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Categories: Charging System | Engine Electrical System

The Datsun 1200 Alternator uses an external voltage regulator. This is a precision device with magnetic coils and moving contact points. They generally last about 10 years of normal driving. B110 regulator uses spade terminals, and so is different from B210 which uses round pins. It controls the alternator output to between 13.5-15.0 volts, by rapidly vibrating moving point. Newer regulators are available that are more reliable with solid-state circuits (no moving parts).



B110 uses a 6-spade terminal Type used for 510, 521, early 620, early B210 etc.

RockAuto 23500-29901/23500-29902, 23500-29911, 23500-N3300
th_VR121.jpg th_VR121_.jpg th_VR121_connector.jpg


Voltage regulator is mounted in the engine compartment:

Early: left side
Late:  right side

It is in the same location for coupe and sedan, RHD and LHD.



Voltage regulator is mounted in the engine compartment, on the left strut tower. It is the rectangular box mounted on front of the strut tower (left strut, right side of photo)


374.jpg 1455.jpg 1521.jpg 2298.jpg


1974-up 1200 utes have the alternator on the other side of the engine. The Voltage Regulator was typically placed on right side (next to battery). This is probably why they placed the battery straight on these utes.



The regulator should keep voltage output of the alternator between 13.5 - 15.0 volts (exact specs vary by temperature, see the Factory service manual.

16102.jpgAlbum 16102

If out of specification, it is possible to adjust the regulator. But it is far easier to replace the regulator.

First: Check the Fuse Box. The 'M' fuse (Meter/Reverse/Regulator) powers the voltage regulator. If this fuse is bad, the alternator will not charge the battery.

To test the Regulator:

  1. Put a voltage meter across the battery terminals
  2. With engine running, at 1200 RPM:
    • Battery fully charged: Voltage must be at least 13.5 volts or battery won't be properly charged
    • Battery low: Voltage must be at least 12.5 @ 1100 RPM with headlights on
    • Voltage must be no higher than 15.0 volts or battery damage may result

If it is too high (over 15.0 volts):

  • Test output at Regulator, from A terminal and Ground terminal.
  • If in spec here, but too high at the battery, there is a wire corrosion problem somewhere. Clean and inspect the wires at battery, cable and wiring harness.
  • If output is too high at regulator, replace or adjust Regulator

If it is too low

  • Test output at Regulator, from A terminal and Ground terminal.
  • If in spec at the regulator, but too low at the battery, there is a wire corrosion problem somewhere. Clean and inspect the wires at battery, cable and wiring harness.
  • If too low at the regulator, peform Regulator Bypass Test

Regulator Bypass Test

  1. With key off, unplug T-connector from the alternator
  2. Insert jumper wire with spade connector to the F terminal in the T-opening.
  3. Place voltage meter across battery terminals
  4. With engine running, touch jumper to A terminal on alternator (+12V).
    • If voltage jumps to 13.5 volt or more, the regulator is bad
    • If voltage is still low, replace or repair the Alternator. Often it just need a $10 brush replacement.


Also see Alternator Wiring


Voltage for a standard lead-acid automative battery depends on temperature. Here are specs for a typical a Datsun regulator:

Temperature, Voltage
14F  14.4-15.5
32F  14.5-15.5
50F  14.8-15.3
68F  14.2-15.2
88F  14.0-15.0
104F 13.9-14.9

24526.jpgAlbum click to view 24525.jpgAlbum click to view

Why does the voltage exceed 12 volts? Because of lead-acid battery requirements.

Battery University: The correct setting of the charge voltage limit is critical and ranges from 2.30V to 2.45V per cell.

Temperature changes the voltage ... a colder temperature prefers a higher setting.
2.30V x 6 cells = 13.8 volts
2.45V x 6 cells = 14.7 volts

To extend service life, the voltage regulator may be adjusted to the lower range. The higher voltages provide faster charging, but at reduced battery life.

Advanced Battery

If you have an advanced lead-acid battery (AGM, Optima, etc), follow the manufacturer's recommendation on charging voltage. While these batteries can handle a wider range of charging voltages, they will last longer if the voltage is tightly controlled.

For example, Optima recommends this charging for thier AGM batteries:

Optima Yellowtop - Alternator: 13.65 to 15.0 volts, no amperage limit
Optima Bluetop/Redtop - Alternator: 13.3 to 15.0 volts, no amperage limit





Part Numbers

B110 uses Male Blade Terminals, six terminal

Female rectangular connector
12V Negative Ground
23500-N3300 (same as 70-73 240Z, and 68-73 510)
* replaced by: 23500-29906 $103 USD (which also replaced 70-72 521 pickup) 
* 23500-29902 -0972 <> 23500-29901
* 23500-N3300 1072- <> 23500-29902 $84.12
* 23500-29911 $75.67
* Standard Motor Products VR121 $30 USD
* Airtex/Wells 1V1250 $18 USD
* AcDelco E661 (88925052) $40
* GP Sorensen 265003 $48 USD


See main article: Voltage Regulator Interchange

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This page has been accessed 46,413 times. This page was last modified 11:06, 20 March 2017. Content is available under Datsun 1200 Club.