How to Troubleshoot a Metal Halide Light Fixture

Written by chris deziel Google
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How to Troubleshoot a Metal Halide Light Fixture
The light from a metal halide lamp is close to natural sunlight. (große fenster image by Elisabeth Klein from

Metal halide lamps belong to a family of high intensity discharge (HID) lamps that includes mercury and sodium lamps. Like fluorescent lamps, HID lamps produce light by the excitation of a gas confined between a pair of electrodes and require a ballast to limit current draw and to provide proper starting and operating voltages. If your metal halide lamp does not start or burns irregularly, there may be a problem with the ballast or the bulb. Metal halide bulbs are long lasting, but they do eventually wear out.

Skill level:

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Things you need

  • New bulb
  • Screwdriver
  • Voltage tester

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  1. 1

    Check the lamp. It may be loose in the socket. If so, tighten it. If you suspect the lamp may be blown or defective, try another lamp.

  2. 2

    Read the ballast specifications on the nameplate, including voltage, wattage and lamp type, and be sure they agree with the characteristics of the bulb.

  3. 3

    Turn off the breaker supplying the lamp and tighten the connections on the ballast with a screwdriver. If the lamp has never been operational, make sure the wiring agrees with the diagram on the ballast label. Be sure the voltage supplied to the ballast is correct. Some ballasts require 240-volt power, supplied by two hot wires carrying 120 volts each and connected to two separate breakers in the panel.

  4. 4

    Look inside the ballast for a blown fuse and replace it with a new one. Check the ballast output with a voltage tester. Turn on the lamp and touch the ends of the tester leads to the lamp electrodes with the bulb in place, then remove the bulb and make the same test. You should get voltage readings in both cases that agree with the output specified on the label.

  5. 5

    Turn off all other elements on the same circuit as the lamp and then try it. If it goes on, the circuit is probably overloaded. Wire the lamp or some of the other elements to a different circuit.

  1. 1

    Check the voltage of the ballast with a voltage tester if the bulb starts slowly. Do the test with a lamp in place and with it removed. If the readings agree with the ballast specifications, replace the lamp.

  2. 2

    Compare the lamp specifications with those of the ballast if the lamp has a short life. Also, be sure the lamp is specified for the orientation in which you are using it. Some lamps have to be installed base up (BU) and some base down (BD). Check the casing and metal parts of the lamp for damage.

  3. 3

    Check the voltage of the ballast with a voltage tester if the lamp intensity is too low, and be sure the ballast and lamp specifications agree. Clean the reflector with a cloth if it's dirty.

Tips and warnings

  • When you switch off a metal halide lamp after it has been burning for a while, it may need to cool down before it will go on again.
  • If the wire connecting the lamp to the house circuitry is too thin, the ballast may not be able to develop sufficient power to start the lamp.
  • Metal halide lamps operate at a high temperature. Always let a lamp cool down completely before you touch it.

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