ASE Air Conditioner Certification Practice Exam 2025 – Comprehensive Test Prep

In determining why the cooling fan operates on high speed but not on low speed, it's crucial to understand the functioning of the fan circuits. The fan typically operates in two different modes: low speed and high speed, with each mode often controlled by distinct circuits or components.

The situation where the high-speed function works indicates that the circuit responsible for high speed, including any relays or direct power input, is functioning correctly. It also suggests that the fan motor itself is operational when greater current or voltage is supplied.

When considering the cause of the fan's low-speed failure, one must recognize that an open circuit at the junction along circuit 15 or any components critical for low-speed operation could prevent the fan from running in that mode. Circuit 15 likely includes connections that are essential for low-speed functionality, while circuit 30 is involved in powering the fan at a higher speed.

A faulty fan control resistor, often used to regulate voltage to achieve low-speed operation, would directly impact the low-speed functionality. If this resistor fails, current cannot flow appropriately to the fan for low-speed use.

Thus, an open within circuit 15 would indeed prevent the low-speed setting from functioning, but the operation on high speed may remain unaffected.

In contrast, circuit 30