GMC Safari heater operates only at two higher speeds, resolved by replacing the blower motor resistor on GMC Safari

Some GMC Safari owners report experiencing issues with their heater only operating at two higher speeds, often linked to a faulty blower motor resistor. Symptoms of this problem include a dramatic decrease in air pressure when the resistor is malfunctioning, although the temperature output of the heater remains unaffected. To diagnose the issue, owners are advised to check the blower motor resistor for any signs of damage. Replacing this component is a common solution to restore proper blower function. Additionally, it is crucial for owners to ensure the blower motor is in good condition and that wiring issues are not the underlying cause. Checking the switch and obtaining the correct wiring diagram are also recommended steps in troubleshooting heater blower problems.