HID Troubleshooting For Lamp Cycling And Low Output
What will cause my lamp to cycle on and off?
This could be an indication that the lamp has reached the end of its life. Replacing the lamp with a lamp specified to operate with the
installed ballast will usually correct the cycling. There could also be other reasons
What will cause reduced light output from my HID lighting?
As HID lamps age the light output decreases. First replace the lamps with those specified on the ballast label. If the lamps have been
replaced and the light output is still low, there are some tests to determine if the ballast is operating properly. Measure the OCV and
short circuit current of the ballast. The value of the OCV and short circuit current is listed on the ballast label. Short circuit current
is measured by shorting the output of the ballast at the lamp socket. This will not damage the ballast as the ballast will current limit
at the value shown on the label. If these two measurements are as listed the ballast is operating normal. If short circuit current is low
and the ballast shows no signs of over temperature operation replace the capacitor. Ballasts that show signs of over temperature
operation should be changed.
How do I determine if a HID ballast is operational or has failed?
First replace the lamp with a known good lamp listed on the fixture or ballast label. If this does not correct the problem, then
measure the input voltage to the fixture and to the ballast to verify the availability of supply voltage at the ballast input. If the
supply voltage exists at the ballast input leads, check for OCV. (Refer to the FAQ in our HID Magnetic - Technical section on OCV) If
the OCV voltage is correct as listed on the ballast label, the problem could be a defective capacitor or ignitor. Change one of these
component one at a time to correct the problem. Generally, if the ballast shows no signs of overheating and the OCV measurement is
correct the ballast is good and there has to be another component failure or a wiring problem.
What further magnetic ballast checks should be undertaken to identify probable causes of inoperable ballasts?
- The following possibilities should be considered and/or pursued:
- Normal ballast end-of-life failure
- Operating incorrect lamps. Use of higher or lower wattage lamps than rated for the ballast may cause premature ballast end-of-
- Overheating due to heat from the fixture or high ambient temperatures causing the ballast temperature to exceed the specified
- Voltage surge from lightening or power source malfunction.
- Mis-wired, pinched, or shorted wires.
- Shorted or open capacitor.
- Incorrect capacitor for the ballast.
- Capacitor not connected to the ballast correctly.
What instruments and test equipment are required for troubleshooting HID Ballasts?
Only the input to HID lighting systems is a sine wave. Once the voltage and current is processed through the ballast and lamp, it is
changed and is no longer a sine wave. As a result of this transformation, only TRUE RMS volt and amp meters will give proper
readings. TRUE RMS clamp-on current meters are also available and are most convenient when reading lamp current.
There are many brands of test meters available. Some indicate RMS and some indicate TRUE RMS on the meter. They are not the
same. Only those that have TRUE RMS will read non-sinusoidal waveforms accurately. The RMS meters will give readings 10 to 20%
low depending on the shape of the voltage or current waveform. Some of these instruments will also read capacitance directly when
connected to a disconnected, discharged capacitor.
There is no field usable meter to test ignitors.
What troubleshooting procedures should be followed for HID ballasts?
At times when an HID lighting system becomes inoperative, a complex and thorough troubleshooting procedure may prove overly
time-consuming. A simple series of checks can decrease this time considerably; a simple check of circuit breakers and power switches
when a bank of fixtures becomes inoperative or a visual check or replacement of a lamp when an individual fixture becomes
inoperative. At other times isolated inoperative fixtures may require systematic procedures to determine the cause of failure.