What will occur if the supply line ruptures?
Rupture of the service line will result in the escape of air pressure, if the brake application is held long enough to cause enough loss of pressure in the tractor system. This pressure drop causes the tractor protection system to close off, exhausting the supply line to the trailer.
What stops pressurized air from flowing back into the compressor from the dry tank?
To prevent the compressor from producing too much compressed air and to reduce the load on the engine, a governor is used in the air brake system. When air-pressure is high enough in the system, the governor causes the compressor to stop pumping air (cut-out).
How can a driver control the trailer brakes independently?
How can a driver control the trailer brakes independently? The purpose of the trailer brake hand valve (30) is to allow the driver to control independently the amount of application air pressure to be directed to the trailer brakes.
What must the driver do when a low pressure warning system activates?
Procedure:
- Ensure air pressure is above 621 kPa (90 psi).
- Ensure ignition key is turned on.
- Press and release the brake pedal (to lower pressure) several times until warning activates.
- Watch the pressure gauges and note the pressure when the low-air warning device activates.
What should you do if you get a low air warning?
If the low air pressure warning comes on, stop and safely park your vehicle as soon as possible. There might be an air leak in the system. Controlled braking is possible only while enough air remains in the air tanks. The spring brakes will come on when the air pressure drops into the range of 20 to 45 psi.
At what PSI should the low air warning activate?
55 psi
What color is the low air pressure warning light?
red
How long should it take for a semi to build air pressure?
Air pressure build-up from 85 psi to 100 psi should take 45 seconds or less. While driving, observe the air pressure gauge during build-up to ensure proper air system operation.
How do you test a low air pressure switch?
Turn the set-point screw counterclockwise as you are applying air pressure to the low pressure switch. If the switch still does not close, the switch is damaged and needs replacement.
How does a low air pressure switch work?
A low-pressure switch is connected to the suction, or “low” side of the system to sense suction pressure. When the pressure in the system exceeds the high pressure switch setting, the switch will open circuit the compressor clutch and the compressor will stop circulating refrigerant.
Where is the low air pressure switch?
Low pressure switches are on the floor, behind the pedals.
What is a low air pressure switch?
A low air warning switch is installed after the supply reservoir to alert you when air pressure drops below a safe level 60 psi (414 kPa). The switch activates either (or a combination of) a buzzer, warning light or a wig-wag (a “flag” that drops into the driver’s view).
What is the purpose of a quick release valve?
The function of a quick-release valve (Fig. 23) is to rapidly exhaust air from the controlled device. It is normally located adjacent to the controlled device, rather than requiring exhaust air to return and exhaust through the control valve.
Where is the low air pressure switch on a Peterbilt?
They are located under the steering wheel on the floor behind the plastic dash in front of your feet. Dont know if there the same on a 377. Mine has two for low air pressure and the one is currently bad.
Where is the low air pressure switch on a Kenworth?
the switch for the low air light & buzzer are in the firewall behind the dash panel where the air guages are.
How does an air brake light switch work?
The air brake system does this with an electric switch that works by air pressure. The switch turns on the brake lights when pressure is applied to the brake pedal. First, it turns on the brake lights when a driver presses the brake pedal. Second, it sends the signal to the vehicle computer that brakes are applied.
What is an air Governor?
The governor (Fig. 20), which is usually compressor mounted, operates in conjunction with the compressor and maintains reservoir air pressure between a predetermined maximum and minimum pressure.
How do you test an air brake switch?
A multimeter can be used to test a brake switch. With the brake pedal released, there should be voltage entering the switch, and no voltage out. After pressing the pedal in and completing the circuit, voltage should be present at both ends of the brake light switch.
What activates the stop switch?
Activates the brake lights when a service brake application is made by the driver.
How do you know if your brake switch is bad?
One of the symptoms commonly associated with a bad brake light switch are brake lights that stay on at all times. If the brake light switch shorts internally it may cause the brake lights to stay illuminated, even when the pedal is not being pressed.
What are the two switches on my brake pedal?
Cruise control cancel/release switch. …
How do you test a brake pedal position sensor?
Place the sensor on just one of the two wires and hold the brake pedal down as you do so. Then test the other wire. If power is connected and the switch is working properly, the test bulbs will illuminate. If it doesn’t light up, the brake light switch is faulty and will need to be replaced.