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The braking system of North American 1200s was fitted with a 5-way splitter combined with a pressure failure warning switch. For safety, if a loss of pressure occurs, the Brake lamp lights up on the dash.
Overview
The switch does not effect brake bias (it's not a Proportioning Valve).
Warning Light Switch (brake line pressure differential)
Datsun 1200 LHD disk brake model. From the north american factory manual.
A warning light is located on the instrument panel to warn the driver when a pressure difference of 13 to 17 kg/cm2 (185 to 242 lb/sq in) exists between the front and rear brake systems.
A hydraulically actuated warning light switch is located in the engine compartment. Both front and rear brake systems are connected to the switch assembly.
When a pressure difference of 13 to 17 kg/cm2 (185 to 242 lb/sq in) occursbetween the front and rear brake systems, the valves will shuttle toward the side with the low pressure. The valve contacts with the switch terminal, the ground circuit for the warning light is completed, and thus the warning light lights.
In this case, correct the hydraulic brake problem and bleed the brakes.
Check the warning light switch assembly for a proper operation. Check the switch assembly for fluid leakage.
NOTE: Do not attempt to repair switch for any reason: replace switch assembly completely.
There are two inputs (front and rear from master cylinder). And three output (two for each front brake, and one output back to the rear brakes. The electrical connector goes to the dash light.
Wiring
The brake lamp is fitted to North America 1200s per US federal law. Other 1200s did not have a lamp in this spot until October 1975.
1972 USA Owners manual (Page 11 ... ):
BRAKE SYSTEM WARNING LAMP
If either half of the dual brake system fails, the brake warning light (BRAKE) glows when brakes are applied. You must stop the car immediately and if you can safely operate with two-wheel brakes, move your car at reduced speed to the nearest service station.
This warning light is also used as the parking brake warning light.
Before starting, if the warning light does not glow when the parking brake and ignition switch are on, have the electrical system checked.
Part Numbers
46100-U5200 ASSY-SWITCH BRAKE INDICATOR <> 46100-26100 $152 USD
* B110 USA
* S30 USA
