The air gauges are located on the engineer's instrument panel and show the main reservoir, equalizing reservoir, brake cylinder, and brake pipe pressures. The tachometer should show 275 RPM with engine idling and 800 RPM with throttle fully open. The gauge shows the temperature of the engine cooling water leaving the engine. Earlier locomotives have two gauges, one for each cylinder bank outlet.
Later locomotives have one engine temperature gauge only.
Engine temperatures should be kept between 150 and 180 degrees, as described in Section 3. When wheels slip the light will flash on and off. The reading shown by the gauge on the engineer's instrument panel is the pressure of the fuel in the line returning from the engine to the main fuel tank. The gauge should read approximately 5 pounds. The gauge indicates the pressure of the oil in the lubricating system at the rear of the engine.