2.3: Instruments
- Page ID
- 49439
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- Speedometer: The speedometer will tell you the speed that the vehicle is traveling.
- Tachometer: The tachometer will tell you the speed of the engine in revolutions per minute (RPM). If you notice in the picture it shows “× 100” that means that the numbers on the tachometer are the number times 100 for example 5 equals 500.
The tachometer is THE MOST IMPORTANT GAUGE when up-shifting and down shifting the truck.
- Fuel Gauge: The fuel gauge will tell you how much fuel is in your tanks, remember commercial trucks can have different size tanks so remember a half tank is not the same in every truck.
- DEF (Diesel Exhaust Fluid) Gauge: The DEF gauge will tell you how much DEF is in your tank; DEF tanks can range from 5 to 20 gallons. You may need to fill the tank daily depending on size and the type of driving you are engaged in, stop and go driving will cause the truck to burn more DEF.
- Voltmeter: The voltmeter gives you a reading on charging system voltage and should be between 13 and 14 volts. If the voltmeter is at 12 or less this could indicate that the alternator is not working properly.
- Ammeter: The ammeter measures current flow in amperes and is an important tool to indicate if the alternator is operating properly. Ammeters are not a standard feature on all commercial trucks.
- Air Pressure Gauge: The air pressure gauge or gauges indicate the air pressure in the primary and secondary air systems. In this picture the primary is indicated by a “1” and the secondary by a “2”. The gauges pictured also have a low air indicator that will come on before the pressure in that system fall bellow 55psi. During normal operation the gauges should operate between 90 and 140 psi. The air pressure gauges are used during the brake inspection portion of the pre-trip inspection.
- Oil Pressure Gauge: The oil pressure gauge gives you the reading on the engine oil pressure, this is important to keeping the engine lubricated and operating properly. During normal operation the gauge should read between 20 and 50 psi.
- Coolant Temperature Gauge: The coolant temperature gauge gives you on a reading the temperature of engine coolant, this is important to keep the engine operating properly. During normal operation the gauge should read between 180 and 200 degrees.
- Engine Oil Temperature Gauge: The engine oil temperature gauge gives you a reading on the temperature of the engine oil. During normal operation the gauge should read at a temperature slightly higher than the coolant temperature. This gauge is not standard on all commercial trucks.
- Exhaust Pyrometer Gauge: The pyrometer gauge measures the temperature of exhaust gases when they are leaving the engine. During normal operation when the truck is loaded the gauge should read between 800 and 1100 degrees. Pyrometers were much more common on older trucks but can be found on some newer units.
- Transmission Temperature Gauge: The transmission temperature gauge measures the temperature of the oil in the differential. Under normal operating conditions the gauge should read between 175 and 225 degrees. This gauge is not standard on all commercial trucks.
- Axle Temperature Gauge: The rear axle temperature gauge measures the temperature of the oil in the differential. Under normal operating conditions the gauge should read between 150 and 200 degrees. This gauge is not standard on all commercial trucks.