Practice Tips #103: Let There Be Operating Lights

Human beings are very visual creatures. We rely on our eyes every day. Dentistry requires a good view of the operating field. Generally, this view is enhanced by good lighting from an operating light.

A dental operating light not only uses a multi-faceted reflector to allow full illumination, even when objects are interposed, it also provides a color-correct temperature (vital in shade matching), so keeping your operating light working is crucial.

As we mentioned in the last issue of Practice Tips, keep spare bulbs and fuses on hand— so you have a ready replacement available when you need it (that’s “when” not “if”). Usually when the light goes out, it’s due to a simple problem, like a blown bulb. What if a new bulb and fuse don’t restore your light? At that point, you really need a multimeter. This inexpensive and handy tool was detailed way back in Practice Tips #25.

After changing the bulb and fuse, the next simple step is to follow the directions in our book, Dr. Did You Check the Breaker, Too? and check your circuit breaker. Make certain the breaker hasn’t been “tripped”— cutting off power to the light. If your breaker has been tripped, you may need to dig further to see if someone plugged another device into the circuit. Usually, a breaker only trips if something is wrong in the circuit or if it is overloaded. Flip the breaker and keep working, but if the breaker trips again, it is time to look more in-depth at the light itself.

Most operating lights have just a few connections. There’s a light socket where the bulb plugs into, a couple of short wires that connect to the socket(s), a power switch (sometimes this also controls the intensity, sometimes there’s a separate intensity switch), a long wire harness through the arm, and a transformer that connects to the power source.

Switches often get sprayed with disinfectant, so they are a common failure point. Wires run through the arms that move up and down, so they are under a lot of stress and are more prone to failure than other components.

Using a multimeter, you need to check each of these junctions in the light for continuity. We recommend a simple continuity test if you have no light, as you need to find where the circuit is broken (rather than checking for correct voltage). Try testing the following components:

  1. The socket (independent of the wiring)
  2. The wires connected to the socket
  3. The power switch (with it turned “on” and at each intensity setting, if applicable)
  4. The wires that come through the arm
  5. If you have a separate intensity switch, check it as well and at each intensity setting. It’s not unusual for an intensity switch to fail at a particular setting (while still working at another).
  6. Lastly, check the main power cord feeding to the light


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Tracing the circuit to find the break is very similar to tracing a clog in the delivery system. It’s all a matter of tracing the lines until you find the break in the circuit.

If you detect no breaks in the circuit in any of these components, then it’s time to look at your transformer. Be careful when checking your transformer, as you’ll need to confirm voltage with it. For assistance with this component, call and speak to one of our techs as transformer specifications will vary depending on the make and model of operating light you have.

Shown: this transformer can be found on the top of the post mounted Celux operatory light

Electrical problems can be intimidating, but if you follow our instructions, you can see they are usually fairly simple to narrow down. Of course, American Dental Accessories has techs available toll-free to talk you through any problems you may encounter as well, so you can proceed with confidence knowing we’ve got your back if necessary.

By following these simple steps, you too can “see the light” all on your own.


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