Electrical 389 Family
Peterbilt Motors Company 6-12
Engine Coolant Temperature The Engine Coolant Temperature gauge indicates the temperature of the engine coolant.
If the coolant temperature exceeds the maximum limits, a red warning lamp in the gauge illuminates and an audible
warning sounds. If the coolant temperature continues to rise, the Check Engine and/or Stop Engine lights illuminate.
Under normal operating conditions the water temperature gauge should register between 165 and 205°F (74 and 90°C).
Under certain conditions, somewhat higher temperatures may be acceptable. The maximum allowable temperature is
220°F (104°C) with the cooling system pressurized, except for certain engines.
Engine, Oil Pressure If the oil pressure drops below the minimum pressure a red warning light in the gauge illuminates,
the Stop Engine light illuminates and an audible alarm tone sounds.
Engine Oil Temperature The Engine Oil Temperature gauge indicates the engine oil temperature. If the oil temperature
exceeds the maximum limits, a red warning light in the gauge illuminates.
Fuel Filter Restriction Pressure This gauge tells you the condition of the fuel filter by indicating the restriction from the
fuel filter to the fuel pump. The restriction is measured by inches of mercury (in-Hg).
Fuel Level, Primary/Secondary (if equipped) The Pri¬mary Fuel gauge and Secondary Fuel gauge (if equipped)
indicate the approximate amount of fuel in each fuel tank. In addition to indicating empty and full, the gauge(s) also
indicate the fuel level in graduated increments. When the fuel level for each tank is below 1/4 full, a red warning light in
the gauge illuminates.
General Air Pressure #1, #2 The General Air Pressure gauge(s) are used for customer installed component applications.
General Oil Temperature The General Oil Temperature gauge(s) are used for customer installed component
applications.
Manifold Pressure (Boost) The Manifold Pressure (Boost) gauge indicates the power the engine is putting out by
showing the amount of turbo boost. If the pressure indicated by the manifold pressure gauge goes down, there may be
something wrong with the engine
Primary and Secondary Air Pressure Gauge The Primary Air Pressure gauge indicates pressure in the rear braking
system. The Secondary gauge indicates pressure in the front braking system. Each gauge indicates the amount of air
pressure in each system in pounds per square inch (psi). On vehicles equipped with metric air pressure gauges, the
gauge faceplate includes a kPa (major) scale and psi (minor) scale. If the pressure in either or both circuits falls below 65
psi, a red warning light in the gauge illuminates and an audible alarm tone sounds when the engine is running.
Suspension Load Air Pressure, #1, #2 The Suspension Load Air Pressure gauge indicates the amount of air pressure in
the air suspension air bags. When the vehicle is equipped with a second Suspension Load Air pressure gauge, the #1
gauge indicates the air pressure in the driver’s side air bags. The #2 gauge indicates the air pressure in the passenger’s
side air bags.
Tractor Brake Application Air Pressure The Tractor Brake Application Air Pressure gauge indicates the amount of air
pressure applied to the tractor brakes.
Trailer Brake Application Air Pressure The Trailer Brake Application Air Pressure gauge indicates the amount of air
pressure applied to the trailer brakes during brake foot valve and/or hand brake control valve applications.
Trailer Reservoir Air Pressure The Trailer Reservoir Air Pressure gauge indicates the amount of air pressure in the trailer
brake reservoir.
Transfer Case Oil Temperature The Transfer Case Oil Temperature gauge indicates the temperature of the oil in the
transfer case. If the oil temperature exceeds maximum limits, a red warning light in the gauge illuminates.
Transmission Oil Temperature, Main The Main Transmission Oil Temperature Gauge indicates the temperature of the oil
in the transmission.
