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Transformer Thermal Over Load FUSE replacement, where to buy 1 ?

gary350

Well-Known Member
It is good I know all transformers and motors now have safety over load fuses these days to keep your house from catching on fire.

Fuse has numbers,

250v - K2

2a 130C

123 UM1

Does the fuse OPEN by temperature or amps or both?

What is the official name of this fuse?

Where can I buy a new fuse local?

I was hoping I could use a 1N4007 diode for a fuse but probably not.

Exhaust fan in both bathrooms stopped working, both motors needed oil now they both turn good again. I bi passed fuse on work bench works both motors run good.








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gary350

Well-Known Member
YES that is it. NO one local has a clue what that is. LOL. Both hardware stores said, people buy new bathroom fans almost every day because the motor stopped running, I had no clue it was something so simple as a hidden fuse.

I wonder how many replacement bathroom fans Lowe's & Home Depot sells very day. How many millions of bathroom fans are sold nation wide every year. If people knew to put oil on motor shaft 2 places once a year motor would last for ever. Factories engineer things to go bad that keeps them in business.

I ordered replacement thermal fuses. New fuse cost less than whole new fan plus less WORK too;
 

schmitt trigger

Well-Known Member
Absolutely correct Gary;

because these fans are usually employed in high humidity environments, the fans that I have had to replace look exactly to the one in your picture.
And again, the shaft has almost seized, and therefore the motor draws a lot of current attempting to turn.....and the double-whammy of not having an airstream to cool it.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
It's a standard thermal fuse - easily available at any electronics parts company (such as RS above) - no good asking at a hardware store, it's nothing to do with them.

However - as far as the fan (or whatever) manufacturer is concerned, it's a non-replaceable item (RS sell them for manufacturing, not so much for repairs) - if it's blown there's generally a reason for it. So if you replace it. cure the fault as well or it will blow again.
 

MaxHeadRoom78

Well-Known Member
Most Helpful Member
That appears to be a shaded pole motor, the most ineficient of the AC variety and run Very Hot, which is normal. ;) .
Check the oilite bearings for drying out.
 

rjenkinsgb

Well-Known Member
Most Helpful Member
Exhaust fan in both bathrooms stopped working, both motors needed oil now they both turn good again.
It appears there may be felt oil pads around the bearing bushes - they are quite common on better made fan motors.

If so, saturating those with car engine oil will help extend the time before it starts to seize up again.
I've found that lighter oils like 3 in 1 and such have a very short term effect in such things, but engine oil works very well.
 

MaxHeadRoom78

Well-Known Member
Most Helpful Member
One of the best for these motors that run at high temperature and tend to dry the bearings out is ATF.
Posseses high levels of oxidation stability to withstand high temps.
Clean the sintered bronze bearings first with Paraffin/Kerosene.
 

KeepItSimpleStupid

Well-Known Member
Most Helpful Member
I had an APC surge supressor that the thermal fuse protected the supression devices, not the protected devices. Stupid.

Hair dryers have them too. I had a hard time finding an air filter material that is about 1/8" thick.. This Conair I have is a nice design. Its easy to clean the filter. It has an integral GFI at the plug. I added a pigtail extension cord.

My bathroom fan has an impeadace protected motor, maybe shaded pole. I've seen them in old clocks and turntables. No capacitor.

Sometimes they are welded in cooking appliances.

I do have to fix the delay on break relay I added in the attic floor above the bathroom ceiling.

The fan is supposed to run for 20 minutes after its turned off. It worked well, when it worked. It did a good job preventing mold.

I also got the heat lamp variety fan. Its installed with a mechanical 20min timer.
 

KeepItSimpleStupid

Well-Known Member
Most Helpful Member
I have to replace a real fuse that is well hidden next to winding of a motor in a can opener. It must have gotten stuck on, so I will be adding an ON/OFF snap switch too.

You cant even buy blades for a can opener anymore.
 

gary350

Well-Known Member
Hair dryers have them too.

.Sometimes they are welded in cooking appliances.
Sometimes I find items that don't work for 25 cents at yard sales it is always a bad thermo fuse. I solder a jumper wire over the bad fuse then & it works.

I bought a kitchen blender 25 cents, fixed it so I can use it in the work shop.

I bought a hair dryer, fixed it to use to dry paint & glue quick for small jobs.

I bought a 10 cent toaster and fixed it. We use it on campground picnic table when camping.

Thermo fuses are in tube audio amp output transformers & power SP transformers these days.

There is a thermo fuse inside the tiny 120v transformer on a microwave oven PC board.

I got 2 free microwave ovens on CL big over the stove cabinet mount, I scraped them for parts. I hope this little PC board transformer puts out 12 VDC I need 12v to turn on a mosfet when 50v PS comes on. When I get time I will see if the transformer works it could be a bad thermo fuse.

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Nigel Goodwin

Super Moderator
Most Helpful Member
Sometimes I find items that don't work for 25 cents at yard sales it is always a bad thermo fuse. I solder a jumper wire over the bad fuse then & it works.

I bought a kitchen blender 25 cents, fixed it so I can use it in the work shop.

I bought a hair dryer, fixed it to use to dry paint & glue quick for small jobs.

I bought a 10 cent toaster and fixed it. We use it on campground picnic table when camping.

Thermo fuses are in tube audio amp output transformers & power SP transformers these days.

There is a thermo fuse inside the tiny 120v transformer on a microwave oven PC board.

I got 2 free microwave ovens on CL big over the stove cabinet mount, I scraped them for parts. I hope this little PC board transformer puts out 12 VDC I need 12v to turn on a mosfet when 50v PS comes on. When I get time I will see if the transformer works it could be a bad thermo fuse.
In decades of repairing microwaves it was VERY unusual to find a duff low voltage transformer.
 

gary350

Well-Known Member
In decades of repairing microwaves it was VERY unusual to find a duff low voltage transformer.
I don't recall ever seeing a microwave oven PC board with no step down transformer. Most test 9v or 10v some are 12v but this transformer it strange look at the drawing. There are 6 relays 1 is marked 24VDC. 24.5vac goes to bridge rectifier = 48.VDC on my meter, the big cap next to transformer is 100uf 50vdc.

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