How to Test a Metal Halide Ballast with a Multimeter

How to Test a Metal Halide Ballast with a Multimeter?

Although metal halide bulbs are long-lasting, still they wear out. So when you begin to experience rapid flickering, dimming, buzzing and changing colors, the fault could be with the bulb, but most times it is a faulty ballast. 

So once these occur with your metal halide lamp, getting a replacement bulb doesn’t have to be your first step. You should have some checkings performed on your ballast.

While checking the ballast, you need to see if there is any burn marks, swollen cases or leaking oil. These faults would help you conclude on the ballast as the faulty part.

You could use a multimeter to troubleshoot your metal halide ballast, which brings us to our topic,” How do you test a metal halide ballast with a multimeter?” 

We have explained a few tests and guidelines that you can carry out on your metal halide ballast. Following the steps below would help you troubleshoot your ballast without any issue.

How to test the high voltage side of the ballast

The primary way of determining the problems of the ballast is by testing it, and for this test to be carried out, you would need a multimeter. Extech EX 330 is a good one (see on And here you can find the list of the best multimeters in 2018

Check for the high voltage side of the tombstones for continuity.

On a typical metal halide lamp, one or two wires goes into each fixture, the yellow or blue wires indicate the power wires, while the white wire would be neutral. To carry out this test is a simple process, you should turn the multimeter to “ohms” settings, and then you can make the meter indicate a direct shot by touching the ends of each probe.

The next thing to do is to touch one probe of the multimeter on the white wire from the ballast and the other on the other colored wire from the ballast, like in the video below. After this step, your multimeter should show a continuous circuit if your ballast is still working correctly, but if it is not, then you might have to replace it.

You should also make use of the multimeter to test the wire pairs and if they test positive but your metal halide lamp doesn’t still come on, then you have to test the low voltage side of the ballast.

How to test the low voltage side of the ballast

To run a  test on the low voltage side of the metal halide ballast, you would begin by removing the nuts from the wires that come from the power feed side of the ballast.

Most of the wires appear to be black and white, so the touch the probes of your multimeter on these wires. If your multimeter shows a continuous circuit, then it is functioning well, but if it doesn’t, it needs a replacement. How to replace a metal halide ballast? Watch the video below.

Before carrying out these tests, you should observe the ballast, by exposing it. To reveal it, use a screwdriver to remove its protective covering, then check it to see if there is a leak on it.  The leaking oil proves that pressure from excessive heat has broken the internal seal, so if you observe any leak, you should replace the entire thing. You can also look inside the ballast for a blown fuse that would need to be replaced.


For safety, the first thing to do before carrying out any electrical test is to shut off the electricity running through it, so you would need to remove the lamp from its electrical source and wait for a few minutes to allow any current stored within the ballast dissipate in the light circuit.

Next, remove the bulb from the tombstones that hold it at each end. While you are removing the bulb, you should know the bulb is extremely fragile, so place them where they wouldn’t get broken.

Well, if you have tested the high voltage of your ballast and it is functioning correctly, then you should examine the low voltages of your ballasts. If both still appears to function properly, you should check the wire connections from the tombstones, as one wire could be the reason why of your ballast is working correctly.

It could also be a case of a loose socket. If this is the case, tighten the bulb and when you notice it is blown, replace it.

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