The light in my GE microwave quit coming on so after pulling the case apart to get at it (great design, guys!), the filament of this 25 watt plug in bulb looks intact. However, a meter across the two male terminal spades shows no continuity.
There's power at the connector supplying the light when the door is open or the oven is running-- so that's not the problem. Could the bulb be bad even when it shows continuity?
Make that ...NO continuity....
bad bulb ........
yes, NO continuity mean bad bulb. duh.
*NO continuity equals a broken filament. Replace the bulb.
Happens often Spend the 2 bucks for a new one.
Hi, Anything is possible. Is there proper voltage across bulb socket when door is open?
Bulbs have a built in fusible link in the base. The filament can look fine and the bulb not work.
Could be, but I'm pretty sure that ALL bulbs don't use a fusable link in the base.
Sometimes the filament will open right where it's welded to a feed wire and stay in position so it looks like it's continuous. Giving the bulb a flick with your finger while observing the filament will let you see it it jump away from the feed wire momentarily.
BTW, the fusable link was/is placed in some bulbs to avoid popping a breaker or fuse if the bulb goes into a "tungsten arc" mode when the filament opens. That arc can cause the bulb to draw MUCH more than it's rated current. If you've ever flicked on a light switch and had the bulb give one VERY bright flash and then go dark, you've witnessed a tungsten arc.
As you've been told already, try a new bulb.
Jeff
You are asking if a burned-out bulb is bad? This is why I don't believe in evolution.
If you stick it in another (more portable) lamp and flick it with your fingernail while it is on sometimes the filament will reconnect and weld itself back in place. This, of course, works better with DC than with AC. I have fixed many incandesant bulbs this way.
OK guys-- off to the appliance parts store. I'll post back later...
Better reread the OP a bit more carefully and The Origin of the Species too ;-)
Parts guy was stumped by the intact filament/no continuity too (see Van's post). But I decided to try a new bulb (for $11.24.
It shows continuity.....and works. Thanks to all for the helpful suggestions.
Charlie Darwin wrote: ...
Might "otter" check on the title of the work...
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Charlie Darwin wrote: ...
Just because you the break was visible doesn't (obviously) imply it was/is intact. Nor, of course, that the fault could be at the connection of one end of the filament to the base, etc., ...
When it doesn't light and measures open, it's pretty clear it's defective.
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What is so special about the bulb that they can get that price? You can probably find it cheaper on the internet but then the S&H would be $10.
If you flick the bulb with your finger, you may see the filament vibrate, usually only on one side of the break.
What happens when you touch the meter leads to each other?
What an imaginative work of fiction!
I just had an auto light like that. The problem was not inside the glass, but between the glass and the mount. That is quite high for a bulb.
Continuity means it should work. No continuity means it is broken. End of story.
The filament is circular going around the circumference of the glass and is supported by 5-6 separate wire posts -- each topped with a loop to support/lock the filament wire.
When touching the meter leads together-- the needle deflects all the way showing continuity.
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