Driver Controls and Instruments indicate overall usage, maintenance and lubrication in- tervals for the engine and engine-operated equipment can be determined by operating hours. Voltmeter, Optional The voltmeter gauge is optional on the control panels without an ICU. On the ICU control panels, the voltme- ter readings are displayed on the lower line on the dash message center. Coolant Temperature Gauge During normal engine operation, the coolant tempera- ture gauge should read 175 to 203°F (79 to 95°C). If the temperature remains below 160°F (71°C) or ex- ceeds the maximum temperature shown in Table 3.1 , inspect the cooling system to determine the cause.
See Section 20.00 of the Business Class ® Trucks Service Manual for troubleshooting and repair procedures. The voltmeter indicates the vehicle charging system voltage when the engine is running and the battery volt- age when the engine is stopped. By monitoring the volt- meter, the driver can be aware of potential charging system problems and have them fixed before the batter- ies discharge enough to create starting difficulties. Engine Oil Pressure Gauge The voltmeter will normally show approximately 13.7 to 14.1 volts when the engine is running. The voltage of a fully charged battery is 12.7 to 12.8 volts when the en- gine is stopped.
A completely discharged battery will produce only about 12.0 volts. The voltmeter will indi- cate lower voltage as the vehicle is being started or when electrical devices in the vehicle are being used. The oil pressure gauge should read as shown in Table 3.2 . CAUTION A sudden decrease or absence of engine oil pres- sure may indicate mechanical failure. Bring the ve- hicle to a safe stop, and investigate the cause to prevent further damage. Do not operate the engine until the cause has been determined and corrected. If the voltmeter shows an undercharged or overcharged condition for an extended period, have the charging system and batteries checked at a repair facility.
On a vehicle equipped with a battery isolator system, the voltmeter measures the average voltage of all of the batteries when the engine is running. When the engine is stopped, the voltmeter shows only the gel cell battery voltage and does not indicate the voltage of the engine- starting batteries. 3.42