Can only using Ohm Meter, we can determine if the bulb is fuse or not

ericgibbs

Joined Jan 29, 2010
8,866
hi,
Usually the working voltage and wattage are marked on the bulb/lamp

Using the formula Resistance = (Volt* Volt)/Watts will give the HOT resistance of the lamp when its operating normally.
The COLD resistance is approx 10 times less.

So a 12Volt , 1Watt lamp would have a HOT resistance of 144 Ohms and its COLD resistance approx 14 Ohms.

E
 

Roderick Young

Joined Feb 22, 2015
408
If it's an incandescent bulb, it should read a few ohms. A fuse will basically read zero. Bulbs don't fail as shorts, in my experience (changed a lot of them in the days of pinball machines), so if you see zero ohms, it's sure to be a fuse. A bad bulb will read infinite ohms, same as a blown fuse, same as nothing connected at all.
 
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