Never assume color coding. Always verify with a multimeter against the pinout diagram in your manual.
When installing or servicing the module, it is critical to refer to the specific Curtis technical manual for the correct wiring diagrams and protection protocols. Because critical components are exposed on standard modules, users must ensure the packaging provides adequate protection for the intended operating environment. curtis 3501 manual
The standard color code for a Curtis 3501 (with microswitch) is: Never assume color coding
The "3501" specifically refers to a family of 24V to 48V DC controllers. Its job is to take battery power and convert it into smooth, controlled acceleration for a DC series-wound motor. Unlike modern AC controllers, the 3501 is analog and robust, designed to survive dusty warehouses and wet loading docks. Because critical components are exposed on standard modules,
Often indicates that the instrument voltage does not match the battery voltage or the V+ is connected to the wrong terminal.