Know Your Fire Apparatus Cab Gauge Numbers

By Frank R. Myers

This is the first of two articles about knowing and understanding your fire truck cab gauge numbers.

Just like a pilot must do an instrument scan, so must the driver of fire apparatus. Cab gauges tell us the status of the apparatus at all times while in motion. They also can tell us when something is about to go wrong before an expensive or catastrophic failure occurs.

It is important to know the parameters of the many truck operating system components to confirm that everything is running smoothly. An impending breakdown or seeing a problem before it escalates too far can be revealed through the gauges.  When you suspect that the gauges are relaying something out of the norm, the readings can help the maintenance/shop personnel troubleshoot, identify, and diagnose the problem easier. Gauges do not lie–except on the rare occasion when the gauge itself is malfunctioning.

While every fire truck is different, the main gauges are fairly standard across the board. They include the following (along with their standard operating parameters):

  1. Engine Oil Pressure: 20 psi at idle, normal operating range of 40-60 psi.
  2. Voltmeter: 13-14 volts normal range, minimum of 12.
  3. Amp Meter: Slightly above “0” – charging – in the green zone.
  4. Air Brake Pressure: Anywhere between 80-120 psi (preferably 100-120 psi).
  5. Fuel Level: ollow your department’s SOP. Never run until empty.
  6. Engine Coolant Temperature: 165-200 degrees Fahrenheit, depending on the engine manufacturer.
  7. Transmission Oil Temperature: 160-200 degrees Fahrenheit.
  8. Diesel Exhaust Fluid: Keep above ¼ and never let it read empty.

When the truck is started, all gauges should move. The indicator needles should move the full range from left to right, and all indicator lights should illuminate. This is known as “proving out.” It is a diagnostic check. If any gauges do not move or any lights do not turn on, report it immediately. 

Always refer to your truck’s chassis manual for normal operating parameters and follow your departments SOPs and shop guidelines.

The second article in this Cab Gauges series will discuss in more depth what the gauges are and what their readings can tell you.

FRANK R. MYERS is a retired lieutenant with Miami (FL) Fire Rescue, where he served for 32 years. Before his retirement, he served at the Training Center for six years as the Driver Engineer Instructor. He works as a consultant for PSTrax.com, a technology service that helps fire departments across the country automate their apparatus, equipment, and inventory checks.

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