Question: Modern air brake systems combine three different systems into one. They are the service brakes, the parking brakes, and the: Emergency brakes. Foot brakes. S-Cam brakes. None of the answer choices are correct Why Your Answer was Incorrect: Foot brakes are a part of the service brake system, but not a sub-system itself. 5.1 The Parts of an Air Brake System Question: What does the air compressor governor do? It controls the speed of the air compressor. It controls when the brake chambers release pressure. It controls the air pressure applied to the brakes. It controls when air is pumped into the air tanks. Why Your Answer was Incorrect: The governor does NOT control the speed of the air compressor. It controls the timing of the compressor. Question: If your vehicle has an alcohol evaporator, what should you do every day during cold weather? Replace the alcohol in the evaporator with fresh alcohol. Clean the air filter with alcohol. Check the oil for alcohol content.