ABYC Diesel Practice Exam

What is the most likely cause if the exhaust blower switch is activated, but the blower sound is abnormal and the breaker trips?

1. Blower motor armature bearings are seizing

2. Faulty electrical connections

3. Insufficient power supply

4. Wrong blower type installed

The correct answer is: Blower motor armature bearings are seizing

When the exhaust blower switch is activated and an abnormal sound is heard from the blower, coupled with the breaker tripping, it suggests that there may be a mechanical issue within the blower unit itself. A likely cause of this scenario is that the blower motor armature bearings are seizing. Seizing bearings create increased resistance in the motor, leading to excessive current draw as the motor struggles to operate. This surge in current can overheat the motor and trigger the circuit breaker to trip as a protective measure, preventing potential damage to the electrical system or the motor itself. The abnormal sound is often indicative of a mechanical failure, such as grinding or scraping, which would be consistent with seized bearings. In contrast, other options may relate to electrical issues but do not specifically explain the combination of abnormal sounds and breaker tripping as clearly as the issue with the bearings. While poor electrical connections could lead to malfunctioning, they typically wouldn’t cause an abnormal sound unless severe arcing or burning occurs, which is less common. Similarly, insufficient power supply could affect motor performance but is less likely to result in abnormal sounds indicative of internal mechanical failure. Lastly, having the wrong blower type installed would more likely result in improper function instead of causing a mechanical fault with associated sounds