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Make Diagnoses with an Infrared Gun

The ability to quickly determine the temperature of a part without any disassembly is a wonderful aid when things go wrong.

All it requires is an infrared temperature gun and a dose of logic about how the component functions. In some cases, heat will be an indication of a problem. In other instances, it will be a lack of temperature. Think it through.

Following are some common diagnoses you can perform with an infrared gun and the expected results.

  • Engine misfire: To determine which cylinder is misfiring on either a gas or a diesel engine, measure the temperature as close to the exhaust port of the cylinder head as possible. Compare this reading with the other cylinders. If the cylinder is not burning the fuel (bad ignition wire, fouled spark plug, failed or lazy injector/nozzle), it will be cooler than the others. Lean bores will be hotter.
  • Confirmation of engine coolant gauge: Measure the temperature at the location of the sending unit (usually it is a single wire sensor). It should read similar to the temperature of the gauge. If not, the sending unit, gauge, or wiring is the problem.
  • Engine oil temperature: To confirm engine oil temperature, shoot the oil pan and, if possible, the oil filter. There will be a small amount of heat loss, but it will be close enough for diagnostics.
  • Blockage in radiator, intercooler, oil cooler, or heater core: Follow the liquid or airflow into the heat exchanger. Liquid or air should drop in temperature as it travels through it. Look for either excessively high or low temperature spots to find a blockage.
  • Excessive brake drag: Measure the drum or rotor temperature to find a dragging brake shoe or pad.
  • Stuck thermostat (closed or open): When stuck closed, the temperature will be high on the engine side of the thermostat and low on the outlet. If stuck open, it will be almost the same on both sides of the flow in and out.
  • Tires: When balancing tire pressure on a machine that is in the sun, keep in mind that for every 10°F. change, the pressure is skewed by 1 psi. For example, the ambient temperature is 60°F. and you want 32 psi in all tires. The temperature of the tires in the sun is 90°F. Those will need to read 35 psi on the gauge to be 32 psi when they drop to 60°F.  It is not a perfect test, but it is very close for most purposes.
  • Bearings: A bearing will run hotter when it is starting to fail. Find a noisy bearing on any machine by taking its temperature.

You can also use an infrared gun to measure soil temperature at planting depth. The possibilities for detecting problems and heading off repairs using an infrared gun are endless if you apply typical American farmer ingenuity.

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