Supplies power to the defrost heater and thermal fuse when the timer enters the defrost cycle.
Before diving into the wiring diagram, it is essential to understand what the defrost timer is doing. The defrost timer is the "traffic cop" of your refrigerator. It dictates when the compressor runs (cooling mode) and when the defrost heater turns on (defrost mode).
If your timer sends voltage to Terminal 4, but the heater never turns on, test the bimetal thermostat (clamped to the evaporator coil). It should have continuity below 40°F (4°C) and open above 60°F (15°C). If it is stuck open, replace it—not the timer.
Most standalone defrost timers have four primary terminals. While colors can vary slightly between Samsung model series (like French Door, Side-by-Side, or Bottom Freezer), the logic remains consistent.
Connected to the neutral wire to power the timer’s internal motor.
If the timer fails in the "compressor" position, your coils will ice over completely, blocking airflow. If it fails in the "defrost" position, the heater will stay on, and the fridge will warm up (often triggering a thermal fuse to blow).
The timer’s internal motor rotates a cam that keeps terminals 1 and 4 connected, allowing the compressor to run.
Pin numbering (looking at bottom/terminal side, latch at top):
*These timers are usually devices. Most common is 8-pin, 120V AC .
This is the simplest. It has three terminals labeled or L, N, C .
If your refrigerator isn't defrosting, you can manually test the timer: