Automotive Electronics Practice Test

What is the most likely cause if all brake lights are dimmer than normal according to Technician A and Technician B?

1. Bad bulbs

2. High resistance in the brake switch

3. Both bad bulbs and high resistance

4. Neither bad bulbs nor high resistance

The correct answer is: High resistance in the brake switch

The assertion that high resistance in the brake switch is the most likely cause for all brake lights being dimmer than normal is correct. When there is high resistance in the brake switch circuit, it can impede the amount of current flowing to the brake lights. Since brake lights are designed to operate at a specific voltage and current, any increase in resistance can lead to a significant drop in current, resulting in dimmer lights. This scenario is common in vehicles with older wiring or connections that may corrode or oxidize over time, leading to increased resistance. In such cases, the brake lights may still function but will shine less brightly than expected due to insufficient power reaching them. While bad bulbs can also cause dim lighting, it is less likely that all brake lights would arise from bulb failure at the same time unless they are very old or have not been replaced for many years. High resistance is a more probable and systemic issue affecting the circuit itself rather than the individual bulbs. Thus, identifying and addressing high resistance in the brake switch would be a more critical step in resolving the problem of dim brake lights.