If a blower motor works on high but not on low or medium, where is the problem likely found?

When a blower motor operates properly on high speed but fails to function on low or medium speeds, the issue typically lies within the resistor block. The resistor block is responsible for controlling the voltage supplied to the blower motor at different speeds. When the motor is running at high speed, it receives full voltage, bypassing the resistor. However, when it is intended to run at lower speeds, the current must pass through the resistor block, which reduces voltage.

If the blower works on high but not on low or medium, it indicates that the blower motor itself is functioning correctly, as it operates at the highest setting. Thus, the malfunction can be attributed to a failure in the resistor block, which is not providing the necessary reduced voltage for the lower speed settings. This reasoning supports the conclusion that the resistor block is the likely source of the problem.