Electronic component in refrigerator

[Bumblebee001]

Hi,

The bulb in my fridge-freezer exploded. I carefully removed the metal screw remains after unplugging the fridge. Replaced the bulb but it still would not light up after plugging back in. I tested with a meter and there appears to be a voltage of 230V across the terminals. I turned off again and gently adjusted the copper terminals thinking that it was a matter of non-contact with the bulb end. Again the bulb which I tested separately still does not light when screwed in.

There is a component in series with one of the leads leading to the socket into which the bulb is screwed. It looks as though it is somewhat burned. It has these letters and numbers written on it: Q89L 55C 11888.

Can anyone help me solve this puzzle? Why won't the bulb light up if there is the correct voltage, good contact and a good bulb? Is it inadequate current due to the damaged unidentifiable component? What could this component be?

If it helps the fridge freezer is a Westpoint BKF 405.

 

[Bumblebee001]

The mysterious component is white, cube like, perhaps 8mm x 5mm x 2mm (just to give an idea of how small it is, not exact measurements).

 

[Electrobrains]

1. What kind of bulb is involved? A normal incandescent type, neon bulb or LED light?
2. Did you secure that the new bulb is not broken?
3. If original is a neon bulb and you try to plug in an incandescent bulb, then the component is probably a resistor.
4. It could be a resettable fuse that is damaged

 

[Bumblebee001]

1. What kind of bulb is involved? A normal incandescent type, neon bulb or LED light?
2. Did you secure that the new bulb is not broken?
3. If original is a neon bulb and you try to plug in an incandescent bulb, then the component is probably a resistor.
4. It could be a resettable fuse that is damaged

1. Normal incandescent bulb
2. new bulb works fine - tested on a different socket
3. Not the case
4. resettable fuse? If a fuse, I would not expect a voltage reading at all in the terminals within the socket into which the bulb screw.

 

[Electrobrains]

4. resettable fuse? If a fuse, I would not expect a voltage reading at all in the terminals within the socket into which the bulb screw.

A resettable fuse automatically returns to conductive state when current is removed. If it's damaged (you wrote the bulb "exploded"), it might have got damaged and received a higher resistance, thus reacting at a lower current and directly tripping when a new bulb is installed.

Do you have a multimeter? If yes, then measure the resistance of that component without power (or the voltage over the component when power is on and the bulb is installed -WARNING DANGER!).

 

[Bumblebee001]

A resettable fuse automatically returns to conductive state when the current is removed. If it's damaged (you wrote the bulb "exploded"), it might have got damaged and received a higher resistance, thus reacting at a lower current and directly tripping when a new bulb is installed.

If damaged, would it "trip"?

Where can I purchase such a fuse? What "value" should I be looking for? Can it be replaced by something easier to find - eg an ordinary 3A fuse?

What purpose does it serve? I have never seen bulbs "protected" by such components.

 

[Bluejets]

Show a photo of the device.

 

[Electrobrains]

As I wrote, if possible, measure the component with a DMM.
Sure, you can exchange a resettable fuse with a normal fuse.
Resettable fuses: https://www.digikey.com/products/en/circuit-protection/ptc-resettable-fuses/150

 

[Tha fios agaibh]

I suspect its a thermal fuse of some kind.
A exploding lamp is indicative of a short circuit or a bad connection causing arcing.

I would unplug power and check for continuity with an ohmmeter or continuity tester between the lamp socket and everything upstream.
I suspect the mystery component is blown-out, but it may have taken a hit because of bad contacts in the door switch. If you have continuity, try jiggling the switch plunger and see if your meter reading bounces.

 

[Electrobrains]

A thermal fuse in a fridge? In a boiler, tumbler, radiator - yes, or possibly on the compressor in the fridge, but in series with the lamp...

P.S. Could it be that component in fact IS THE SWITCH...??? Maybe a reed contact reacting to a magnet when the door is shut?

 

[kellys_eye]

I tested with a meter and there appears to be a voltage of 230V across the terminals.

Whatever the mystery component/device is, it's not stopping the supply getting to the light....... phantom voltage measurement???

 

[Bluejets]

I think the Op has himself confused BUT it is possible to get a voltage reading when not loaded and then too much resistance to drive the lamp, such as a carbon burnt up piece of whatever in series.
Must admit I've never seen any type of fuse in line with a frig bulb though.

Don't know why the big secret around showing us a photo though.
Surely that would be of some help.

 

[debe]

This is probably the component marked 714, Thermal relay as to why its in the lamp circuit I have no idea. Don't understand why the OP is uncooperative when asked for information. The component is probably damaged to the point of passing voltage, but very little current.

 

[Tha fios agaibh]

Whatever the mystery component/device is, it's not stopping the supply getting to the light....... phantom voltage measurement???

Yes, it's very likely a phantom voltage.

A dvm reading can be misleading. Yes, there is actually 230v there, but the circuit is unable to pass any significant current when under a load.
In situations like this I always use a loaded meter.

 

[Bumblebee001]

I took this video of the problem: https://mega.nz/#!lRxhhQBK!eMRfBG5KVKlwdfC-Nkyjmzru3L-FaPFn0rQ6lsUlzZ0

 

[Tha fios agaibh]

Looks like a loose connection. Probably in the lamp socket. The wire can be pulled back out of push in connector by pulling and twisting it at the same time. (This takes a bit of force with your hand.)
Sometimes you get lucky by cutting off about 10mm of the wire, stripping insulation back and inserting it back in the lamp socket by pushing.

 

[Bumblebee001]

If you see the whole video clip you will see that the component is damaged. Part of the cover pealed off and the component smokes if bulb is left on for a longer period of time. This needs to be replaced but I have not managed to get any information about it to be able to replace it.

I have seen sparks (like when an insect gets sizzled in an electronic insect trap) on the exposed side.

 

[Tha fios agaibh]

You can get a replacement, but IMHO
If it was me I'd probably just cut it out of the circuit.
Most refrigerators don't have thermal fuses for the lighting circuit.

 

[Bumblebee001]

I was tempted to do just that but I'm sure the manufacturer added this component for a reason considering that most would not add anything extra that would increase the cost of production!

The values shown in the picture posted are different from mine. Would it make a difference?

 

[Tha fios agaibh]

It would be safer, yes. The intent of the manufacture adding the thermal is to protect when someone puts in the wrong light bulb.

No, The most important number is 55c which is the temperature it will limit.