Aquatics Unlimited: Articles: Troubleshooting Fluorescent Lights
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Troubleshooting Fluorescent Lights

for the week of 4/2/98

If the light goes out in the hallway, you can usually just screw in a new bulb and in moments, you can shout, "Lux fiat!" ("Let there be light!"), and flip on the switch. But when a fluorescent aquarium fixture goes out, there may be several possible causes. Here are some troubleshooting tips:

A bad bulb will often be blackened at the ends and will start, but slowly. If the fixture is an older model with no starter (the switch must be held in to start the bulb), the lamp often turns itself off after a few minutes or hours. If the fixture has a starter (little silver can, most common size if FS-2), the lamp will often turn off, restart, and turn off repeatedly.

A bad starter will likely result in one of two extremes: either the lamp will not start at all (although oftentimes the ends of the bulb will glow) or it will start promptly, but begin flashing as the starter continues to attempt to start the bulb, even though it's already on.

In older models with no starter, failure of the four-wire switch also results in starting failure. If the starting circuit (usually red or blue wires) fails, the bulb may show a faint glimmer throughout. If the main circuit (black wires) fails, the bulb ends will glow, but upon releasing the switch, the bulb goes dark.

A bad ballast (transformer-looking device sometimes found on the cord on older models, but found under the reflector in many newer fixtures) is probably the worst case scenario. Since the ballast's job is to reduce the amount of current that goes to the bulb, a damaged ballast often results in immediate damage to the bulb. There is usually a flash of light, and occassionally even an implosion of the bulb itself. The aquarist might not be there at the moment of destruction, and assumes the bulb merely needs to be replaced. Unfortunately, the new bulb too is destroyed in seconds, and the aquarist learns an expensive lesson.

If the fixture simply does nothing, it may be any of the above, or a number of other things, including a disconnected or broken wire, bad plug, bad switch - and hey, don't forget to check if it's plugged in! Sometimes it's best to take the whole light fixture, bulb and all, into the shop and let the dealer swap a few parts until he finds the problem.

Last but not least, keep in mind that an aquarium light is a 110 volt electrical fixture sitting two inches above a container of water. Unplug it before attempting any repairs, and be sure everything's back in order before re-installing it.

Submitted by: Jim Kostich

"Tip of the week" appeared regularly in 1999 and 2000.

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