What are some automatic drain valves furnished with to avoid freezing in freezing conditions?
- An electric heating element ✓
- Hot air from the air compressor
- An anti-freeze injection system
- Heat from the vehicle's heater
Answer: A. An electric heating element
Automatic drain valves may come with an electric heating element to keep them from freezing in cold weather.
Why this is the answer
The handbook describes automatic drain valves, sometimes called spitter valves, that briefly release collected contamination as reservoir pressure changes. It then notes that some of these valves are fitted with an electric heating element specifically to stop them freezing when the weather is cold. That matches the answer given, and the same heating-element detail appears in the air dryer section, so the idea of electric heat for cold-weather protection is consistent across the air brake chapter.
Why the other answers are wrong
- B. Hot air from the air compressor — The passages never mention routing hot compressor air to the drain valves for freeze protection.
- C. An anti-freeze injection system — No anti-freeze injection system is described for automatic drain valves in the passages.
- D. Heat from the vehicle's heater — The passages do not say drain valves are warmed by the vehicle's heater; the heat source named is electric.
Remember it
Cold-weather protection on air brake parts in this chapter is electric heat, not engine or heater warmth.