Start by checking the "Possible Causes" listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector's pins.
The cost to diagnose the B12B2 Mercury code is 1.0 hour of labor. The auto repair's diagnosis time and labor rates vary by location, vehicle's make and model, and even your engine type. Most auto repair shops charge between $75 and $150 per hour.
Under normal operation, the blower motor relay coil receives ignition voltage through the circuit. The coil receives ground from the Electronic Manual Temperature Control (EMTC) Module through the circuit if any function selector position but OFF is selected. Voltage is supplied to the relay switch contact. When the relay coil is energized, the voltage is delivered to the blower motor through the circuit. Ground for the blower motor is provided through the circuit from the blower resistor or the blower switch (HI). The blower resistor and blower switch are grounded through the circuit. The module senses no voltage on the blower motor control Pulse Width Modulation (PWM) circuit, indicating an open or a short directly to ground.
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