Test N: The Blower Motor Does Not Operate Correctly

PINPOINT TEST N: THE BLOWER MOTOR DOES NOT OPERATE CORRECTLY

N1:

N2-N5:

N5-N7:

N7-N8:

Normal Operation
Under normal operation, the blower motor relay coil receives voltage through circuit 181 (BN/OG). The coil receives ground from the electronic automatic temperature control (EATC) module through circuit 364 (BK/LG) if any position but OFF is selected. Voltage is supplied to the relay switch contact through circuit 181 (BN/OG). When the relay coil is energized, voltage is delivered to the blower motor through circuit 371 (PK/WH). Ground for the motor is provided through circuit 515 (OG/RD) from the blower control module. Ground for the blower control module is provided by circuit 57 (BK).

The blower motor control module receives a 1-2 volt signal from the EATC module through circuit 752 (YE/RD) to determine the desired blower motor speed. The EATC module receives a feedback voltage from the blower motor control module through circuit 260 (RD/OG) to determine actual blower motor speed. When the highest blower motor setting is selected, the EATC module sends 12 volts to the blower control module through circuit 754 (LG/WH).

Possible Causes
- An open, short to voltage, ground or together in circuits 260 (RD/OG), 752 (YE/RD) or 754 (LG/WH)
- A short to ground in circuit 515 (OG/RD)
- Blower motor control module
- Electronic automatic temperature control (EATC) module