Common Signs It's Your Ballast And Not Your Bulbs

Testing Ballast Function with a Multimeter

A multimeter set can help you tell if a ballast is bad by allowing you to test its function. A multimeter is an instrument designed to measure electric current (amps), voltage, and resistance (ohms). Most devices are digital, but some may be analog. They are user-friendly and versatile, making them a simple tool to test ballasts. Of course, proper safety precautions should always be taken when working with lighting fixtures and electricity.

Prior to testing ballasts with a multimeter, remove the ballast cover so you can access the input terminals. To check the voltage of a ballast, turn on the multimeter and select the appropriate voltage range. Place the probes on the input terminals or the leads connected to the ballast, ensuring they make adequate contact with the metal parts of the ballast's terminals. If the multimeter reads a voltage close to the rated voltage, it indicates your ballast is receiving adequate power. However, if there is no voltage or the reading is significantly lower than the rated voltage, there may be a problem with the electrical power supply or wiring.

Once you have confirmed the system is receiving power, you can test the resistance of the ballast. First, ensure that the electrical power to the fixture is off, and remove the ballast cover, if the ballast is not already exposed. To set up the multimeter, turn it on and select the ohm setting. Place the probes on the input terminals or the leads connected to the ballast.

If the ballast is still functioning properly, an analog multimeter has a needle that will sweep across the measuring scale to the right. If the ballast is bad, there will be no measurable resistance and the needle won’t move. For digital multimeters, the digital readout will typically read a “1” when it doesn’t measure resistance.

Using a multimeter successfully is often a test of your knowledge of electricity, the ballast specifications, and your analytical skills, making this option a bit more tricky.

Common Causes of Ballast Failure

The environment surrounding the fixture is often the primary reason ballasts fail prematurely. Heat and moisture are enemies #1 and #2 to your ballast. Every ballast has an ambient operating temperature range and UL location rating. When it’s too hot or too cold, the ballast can burn up or fail to start your lamps at all. Excessive heat combined with prolonged condensation inside an electronic ballast can cause corrosion.

Some may suggest removing the parts of the ballast casing and cleaning the electrical board, which may work for those knowledgeable and experienced in working with electronic fixtures. However, if you are unable to put the electronic ballast back together, you will be looking for a new ballast. Not to mention potential safety concerns.

To avoid issues with your ballast due to heat and moisture, make sure the fluorescent light fixture has a ballast that is UL rated for its location, particularly if installed in damp or wet areas. The appropriate ballast should be able to handle the high and low temperatures of your local climate.

Lighting Tip: LED drivers often have shorter lifespans than LED arrays or fixtures. Compare light bulb and driver specifications before purchasing.