Electronic vacuum gauges also require some basic maintenance. Their sensor should be cleaned on a regular basis with rubbing alcohol. Pour the rubbing alcohol into the 1/4-inch female fitting and allow sufficient time for it to evaporate.

Electronic leak detectors do not require much maintenance other than regularly cleaning the tips on the probe. However, the sensors can fail, so it is a good idea to keep an extra sensor with the leak detector.

Thermometers are important service tools and their accuracy should be checked on a regular basis. An inaccurate thermometer easily can cause a technician to misdiagnose a problem.

An industry-accepted method of checking a thermometer is to place it in an ice bath using crushed ice and pure water. When adding the water, do not completely cover the ice. The thermometer should read close to 32 degrees F. If the sensor is enclosed in a metal casing, let the thermometer sit in the ice bath for a few minutes so it can stabilize. If the thermometer is within ±1 degree F of 32 degrees F, it is okay. If it is off by more than ±3 degrees F, then it should be calibrated or replaced.

Refrigerant recovery equipment also needs regular maintenance. There are various types of recovery equipment, so always check with the manufacturer for its maintenance requirements. Most manufacturers will require that the filter-drier be changed after a predetermined amount of refrigerant has passed through the system. For example, one manufacturer recommends for one of its machines that the filter-drier be replaced after 300 pounds of refrigerant has passed through it. The oil inside the recovery equipment also needs to be replaced on a regular basis. Again, check with the manufacturer for requirements.

Refrigeration gauges and manifolds are heavily used service tools. The O-rings and valve seats on the manifold should be replaced periodically. When re-placing, make sure to lubricate the O-rings with grease recommended by the manufacturer.

The pressure gauges should be checked to verify their accuracy. This can be done by applying a known pressure to the gauge and comparing it to the pressure read by the gauge. Most gauges will have an adjustment screw to calibrate the gauge to the known pressure. Many technicians use a refrigerant cylinder for this purpose.

When using this method, it is best to use a new tank of refrigerant - a 1-pound cylinder is ideal. Some technicians keep a 1-pound cylinder in the shop specifically for this purpose. The cylinder should be left out at room temperature to allow its temperature to stabilize. Install the gauge on the cylinder, then measure the temperature of the cylinder. It is best to measure the temperature at the lower portion of the cylinder to ensure that the liquid temperature of the refrigerant is being measured. Then, using a pressure-temperature chart, convert the saturation temperature of the refrigerant to its saturation pressure. Then compare the saturation pressure to the pressure on the gauge and make any necessary adjustments.

Refrigeration hoses also need to be maintained. It is a good practice to inspect and, when necessary, change the gasket in the 1/4-inch female fitting on the hose ends. These gaskets can be pulled out easily with the use of needle nose pliers.

Multimeters require little maintenance except for occasionally inspecting the leads. These leads can crack and expose bare wire, causing a dangerous condition: the leads could accidentally cause a short to ground while being used on a live circuit.

Another potential problem is that the leads could break, rendering the meter useless. If and when this happens, it is usually at a time when the meter is most needed. It is wise to carry an extra set of leads and an extra battery for a multimeter. This may save a lot of grief and wasted time on a job. The accuracy of a multimeter should be tested occasionally by testing the different functions on a known source for comparison.

Flashlights and other types of lighting equipment do not need much maintenance. If the lighting equipment has a line cord, then it should be regularly inspected for damage. It is a good practice to keep an extra set of batteries and bulbs on hand. Light bulbs always seem to go bad when you need them the most.

Electronic scales' accuracy should be verified occasionally. This can be done by placing a known weight on the scale and comparing it to the reading on the scale. Many manufacturers will allow the scale to be sent back and recalibrated.

Brazing and soldering equipment should be inspected before using. Look for damaged hoses or loose fittings that may have developed during transportation. Doing this can prevent an accidental fuel spill, which could ignite and cause serious harm to a technician.

There are many other tools used by technicians, such as hand tools and cutting tools, that may not need regular maintenance, but should inspected occasionally for signs of wear. Any tool that shows signs of wear or damage should be repaired or replaced. Using one that is worn or damaged is an unsafe practice and should be avoided. For example, a dull screwdriver is more likely to slip off a screw and cause injury.

Joe Marchese is owner of Coldtronics, Pittsburgh. He can be reached at 412-734-4433, www.coldtronics.com, or joe@rhvactools.com.

Publication date: 11/03/2003