Defrost Controls

HVAC Defrost Controls

The HVAC Defrost Controls category brings together the boards, sensors, and related components that manage defrost cycles on heat pumps and select package units. A properly functioning defrost control keeps the outdoor coil clear of frost and ice, maintains capacity, protects compressors, and prevents nuisance service calls in cold and shoulder seasons. This section is designed for technicians who need the right OEM or high-quality replacement defrost control matched to the exact outdoor unit model and revision.

Here you’ll find classic timed defrost boards, demand-defrost controls that use coil and ambient sensors, combo defrost/defrost-relay boards, and compatible thermistors and sensors for major heat-pump platforms. Many boards include LED diagnostics, test pins, field-selectable timing, outdoor fan relays, compressor outputs, and quick-connect terminals to reduce troubleshooting time. Matching the correct defrost strategy—timer-based or sensor-based—to the equipment is critical for both performance and reliability in cold and humid climates.

• OEM and universal heat pump defrost control boards for split and package units.
• Demand-defrost boards using temperature and pressure inputs.
• Outdoor coil and ambient thermistors for sensor-based systems.
• Defrost-related relays, harnesses, and adapter kits for retrofit work.
• Service-friendly boards with test modes, LEDs, and dip-switch setup.

When selecting an HVAC defrost control, never rely on appearance alone. Confirm the OEM part number, board revision, outdoor unit model and serial, voltage, sensor type, and defrost strategy (time-temperature or demand). For universal replacements, verify the wiring diagram, pinout, and any changes to fan control, reversing valve logic, or low-ambient operation. Use the Compare tools on this page to review application notes, timing options, sensor requirements, and diagnostic features.

Pro tip: Before condemning a defrost board, document frost pattern on the coil, outdoor ambient temperature, coil temperature readings, sensor ohm values, and high/low side pressures. Capture photos of the existing board, wiring, and dip-switch positions. Share that info and we can help confirm whether you need an exact OEM defrost control, a universal replacement, or just new sensors and wiring repairs.