Repairing an electric kettle that doesn't always auto shut off

[Hogwild]

Hi all:

I would like to repair a friend's electric kettle which is showing 2 problems.

I think the first problem is the bimetallic disc that automatically turns off the kettle after the water has boiled.  It only seems to work when the kettle has a small amount of water in it. When you fill the kettle more, it doesn't shut off.

[inse]

What kind of kettle is it, the standard on/off type or an electronic one?
The kettles usually have two separate devices for turning off: the boiling switch is operated by steam and in addition an overtemperature switch which protects it in case of dry operation.
Mentioned here: https://en.wikipedia.org/wiki/Kettle#Electric_kettles
The German article has more details.
In case the bimetallic switch has failed, I think there‘s not much you can do…

[floobydust]

You can replace the temp switch, pics of it can help to source a new one, although just buying a new kettle would be less hassle.

Sometimes you get poor heat transfer to the temp switch - is it tight against the element base? No corrosion?
What I've also seen is a pressure port running from the lid down into the base switch. When the water boils (and the lid is closed) the steam pressure pushes that switch for auto shutoff. It's common for it to get plugged up with lime deposits. Look closely for a hole near the top and make sure it's not clogged.
A thermal fuse is there to cover when the kettle badly overheats.

[coppice]

A common problem is limescale build up in the tube that guides the steam to the sensor which detects the steam. You can get some quirky results with different water levels when that happens.

[Hogwild]

Thanks for all the answers, guys.

I took it apart, and cleaned the contacts. The bimetallic switch seems like it's intact. It's still fairly rigid. It's hard to tell if the plastic bump it touches underneath is worn down or not, but I don't think so.

What common chemical can I use to clean the sensor tube? It's fastened to the metal kettle body, so I'd rather not remove that bond.

Also, when I took apart the handle, I managed to have this spring fall out. I didn't see it fall out until later, so I have no idea where it belongs. Where do I install it?

[IanB]

What common chemical can I use to clean the sensor tube? It's fastened to the metal kettle body, so I'd rather not remove that bond.

Standard kettle/coffee machine descaler, but make sure it doesn't come in contact with anything electrical when applying it. Even vinegar works fine for descaling. Given that it is a tube, you could try sucking up hot descaler solution into a turkey baster and squirting it down the tube. Normally steam goes down the tube and hits the bimetallic strip, so make sure all of that is completely disassembled and removed before trying to clean inside the tube.

[themadhippy]

What common chemical can I use to clean the sensor tube?

forget the fancy chemicals,good ole white vinigar is all thats needed,chuck it in and  let it boil a couple of times. Best to do it outside as the smell WILL  make you crave fish n chips

[IanB]

forget the fancy chemicals,good ole white vinigar is all thats needed,chuck it in and  let it boil a couple of times. Best to do it outside as the smell WILL  make you crave fish n chips

Yeah, but careful with the boiling. I have ruined three kettles by over aggressive de-scaling. The acid solution eats through the stainless steel at joints and seams until the kettle leaks. You would think I might have learned after the first one, but I didn't put two and two together until too late.

So now I use cold vinegar for just a few minutes, with some gentle swirling and scrubbing, followed by a thorough rinse. Cold vinegar does not eat through steel like hot vinegar does.

[Hogwild]

Wait, you mean pour the vinegar directly into the steam tube, or just into the kettle and then boil?

[IanB]

Wait, you mean pour the vinegar directly into the steam tube, or just into the kettle and then boil?

Don't boil the kettle with vinegar in it, it is not necessary.

Putting vinegar in the kettle will de-scale the inside, if it needs it, but will do nothing for the tube.

For the tube to work properly it needs to be clear and unblocked, so it has a free flow of steam.

The end of the tube is visible in your photos. You should be able to see light through it, or pass a wire through it. If it is blocked, it needs unblocking. Carefully squirting vinegar down the tube could help to unblock it. Just be sure to rinse well afterwards, to avoid the vinegar corroding things it should not corrode.

As mentioned at the top of the thread, the general solution if a kettle stops working is to buy a new one. Kettles are not very repairable.

[Hogwild]

I'll give it a try, thanks. I like to keep anything and everything I can out of the landfill. Of course, with an item like this, it needs to have reliable auto-shutoff to be safe, so that is my overriding goal.

[Hogwild]

Before I get back to working on the kettle, does anyone know where that spring goes?

[GLouie]

The spring looks like one of two on the lid hinge on my kettle.

I am confused by the steam tube talk. I took mine apart once, and did not see any connection between the electric mechanism and the water chamber. There is a tube opening for a water level gauge. I confess I didn't look very carefully at the time.

[IanB]

I am confused by the steam tube talk.

Most kettles have a tube running from the top of the boiling chamber down to the bimetallic strip at the on/off switch at the base. When the water boils, steam flows down the tube, heats up the bimetallic strip, and turns off the kettle.

[floobydust]

It pretty complicated - you can search for Strix Ltd. patents on this.  https://patents.google.com/patent/EP2741641B1/en
I thought it was pressure switch, because steam (heat) requires a net flow- but this explains why they get plugged.

OP I noticed the one electrical connection to the stub going to the heating element looks heat oxidized like it's a poor connection that heats up a bit. Check that crimp spade.
Ali has some switch assemblies but a little dodgy looking https://www.aliexpress.com/item/1005005307163145.html
No idea which spring or where it came from, the one you lost.

[IanB]

Before I get back to working on the kettle, does anyone know where that spring goes?

This is usually determined by examination. Something that should be spring loaded, like the on/off switch, is found to be no longer spring loaded. Furthermore, there will be attachment points in the assembly where the spring can go and where it can push against.

From the shape of the spring it is meant to be folded in half and provide a rotating effect.

My guess is that it pushes on the on/off switch to hold it in the off position.

[Gyro]

The spring looks like one of two on the lid hinge on my kettle.
...

Yes, I'm pretty sure it's a lid hinge spring. There can be just one, depending on the kettle.