CDL Air Brakes TestAir Brake System PartsMedium
A technician is performing an inspection on an older commercial vehicle. The vehicle is equipped with an alcohol evaporator. What is the primary function of this component?
- ATo remove oil and other contaminants from the compressed air.
- BTo lubricate internal components of the air compressor.
- CTo increase the boiling point of water in the air system.
- DTo prevent ice formation in the air brake lines during cold weather.
Show answer & explanationAnswer & explanation
Correct answer: D. To prevent ice formation in the air brake lines during cold weather.
Alcohol evaporators are used in older air brake systems (before air dryers became standard) to inject alcohol vapor into the air lines. This alcohol mixes with any moisture, lowering its freezing point and preventing ice from forming and blocking the lines.
Why the other options are wrong
- A. Air dryers are responsible for removing moisture and contaminants; alcohol evaporators handle freezing, not removal.
- B. Lubrication is typically handled by oil from the compressor or specialized lubricants, not the alcohol evaporator.
- C. Alcohol lowers the freezing point, not increases the boiling point of water.
Alcohol Evaporator
A device used in older air brake systems to introduce alcohol vapor into the air lines to prevent moisture from freezing.
- Used primarily in cold climates.
- Replaced by air dryers in newer vehicles.
- Requires periodic refilling with special alcohol.
Memory trick: Alcohol's sip keeps the air lines from a frozen dip!