Automotive Service Excellence (ASE) Air Conditioner Certification 2025 – 400 Free Practice Questions to Pass the Exam

The condition where the blower motor operates on all speeds except low often signals an issue with the resistor pack that regulates motor speed. In a typical blower motor system, there is a set of resistors that provide different levels of resistance for various speed settings. When the low speed is selected, the current passes through a specific resistor, often rated at around 1.8 ohms.

If there is an open circuit in the 1.8-ohm resistor, the blower motor would not receive the necessary voltage to activate at the low speed, resulting in the inability to operate on that setting while still functioning correctly at higher speeds. This is because higher speed settings may bypass some resistors or utilize a direct power source that does not depend on them.

In this situation, the open circuit disrupts the proper function of the blower at the lowest speed but does not affect the other speeds, since those are achieved either through different resistors or a direct circuit that bypasses the resistor arrangement entirely.