Summary: Learn how to
test light bulbs, including LED and fluorescent bulbs, never
throw a good one away again.
To test a
light bulb, you simply need to set your meter to the Ohm position, and put a
meter lead on the very tip of the bulb and the other lead on the side (ground
metal).
It is not important what you get on your meter reading, as long as
it displays some resistance, and it is not reading infinity ohms or
open, then the bulb should be working.
On the rare occasion you get a reading of somewhere
around 0 to 1 ohm, then
the filament inside the bulb probably opened up and
is shorted across both sides.
A typical light bulb has around 18 Ohms, but this amount could
vary among different
size, brightness, and brands.
Fluorescent bulb - If you have a flickering or dead fluorescent tube, then keep
reading for some easy testing tips. One
easy way to tell if a bulb is bad, is if one or both ends of the
tube is very dark, or even black. If so, then
your bulb is either bad, or at the end of it's life.
Another way to test a
fluorescent bulb, is to test the electrodes on both ends of the
tube. Put a meter across the two
metal contacts, and you should get continuity, or zero Ohms. Sometimes you can get a
false reading though if the inner workings of the electrode become
shorted together. If the contacts
on both side are reading ok, but you suspect the bulb is bad anyway,
try this:
Find a known good fixture
to try the suspected bad bulbs in, if they work, then you know it
was probably the ballast or
starter that was not working properly. Note: Most fluorescent
bulbs work as a pair and depend on the
other to work, so move both bulbs to a working fixture to test them.
LED bulbs- To test a LED bulb, first select the diode
setting on you multi meter. Ohm across the bulb contacts, then switch the meter leads to the
opposite bulb wire it was on before. One reading should show an open or no continuity. The other reading
should show a reading of some resistance. If you get a reading both times, then your LED is shorted.
Open both ways indicates an open LED.
For another cool method for checking LED lights,
check out the video below.
