Blower Resistor

Blower Motor Resistor & Control Module – Key Features at a Glance

Blower motor resistors and electronic control modules regulate fan speed in vehicle HVAC systems.

Two types:

• Resistor‑based – uses series resistors to drop voltage; provides 3–4 fixed speeds. Generates heat, needs cooling fins; prone to thermal failure.

• Electronic module – uses PWM (pulse‑width modulation) for infinitely variable, smooth speed control. More efficient, with built‑in overcurrent, overheat, and short‑circuit protection.

Common features: compact design, plug‑and‑play connectors, integrated thermal fuse (resistor type), and diagnostic capability (module type). Operating voltage: 12V (24V for trucks); temperature range: –40°C to +85°C.

Failure signs: fan only works on highest speed (resistor burned out) or no speed variation at all (module failed).

Applications: passenger cars, commercial vehicles, and aftermarket replacements – essential for cabin comfort and defogging.