Inside a cheap eBay fridge freezer thermostat 

"This is where it bursts and squirts unknown chemicals everywhere"! Carry On Clive!

6:14 because it's cold it will be retracted in, said every man.

BigCliveDotCom: Causing shipping managers everywhere to scream when they find out how much it costs to ship to the Isle of Man.

"We don't know what it is, but here it is!" --99% of all online redistributers

Slightly unrelated: my father found previous work done on a commercial fridge, where the owners got a local handyman to fix it.. The handyman cut and joined a capillary pipe with a strip connector because he thought it was a wire and couldn't figure out why it still wasn't working...

This brings back memories of when I was a quality manager, setting up inspection section procedures at a domestic gas boiler manufacturer, in the mid 1980's. Best job I've had in years!

"so you can't RAM IT RIGHT PAST THE END STOP." Gig-gi-ty.

The capillary full length sensing fridge thermostat is designed to be installed entirely inside the fridge, turning the knob only with the door open.

Pretty "cool"! I'd never really thought about these before, but the engineering is really pretty elegant. I also really love the tiny metal accordion.

Love your work Clive. The last thermostat you pull apart you refer to its calibration screw. I think that screw is actually the "differential" temp setting, it works like a sensitivity setting, by adjusting the tension on the spring mechanism. The user-adjustable knob sets the temp at which the thermostat turns off . The sensitivity setting adjusts the temp at which the thermostat turns on, which for fridges and freezers is fixed at about 3 - 5 degrees above the temperature set by the user.

Look up the MSDS (material data safety sheet) for a Honeywell aqua stat. They list their capillary liquid as a mix of Mineral oil, lithium hydrostearate, Zinc Alkyldithiophosphate, and a few other aluminum components, and stearates. I looked it up on a job one day when I had gotten it all over me. Wanted to know if it was carcinogenic. They say it isnt.

His name is "Nowis", Clive!! You wrote it right on the side of the device!! ;-)

The sleeving on the capillary tube is probably to avoid getting kinks. That's a very common failure mode for these things. Most of the waterbed heaters that I've owned over the last too many years have used those stupid bulbs and capillaries. I was really happy to get one that had a thermistor to put underneath the mattress and nice flexible wires instead of that damn bulb. As far as prying up tabs goes, you should get yourself one of the chiplifters from Wiha. They are essentially a miniature crowbar with an end that's maybe 1/8 inch across and curved so that you get leverage to bend things up.

The little "diaphragm" on the second unit is typically called a bellows.

Ah! So that's what those things in my oven are! I've had to remove our oven from the fitted kitchen cabinet four times¹ in the past year to replace the mode selector switch and then one of the heating elements, and I saw these two metal tubes leading from the thermostat dials to each of the two ovens, so they were clearly for temperature sensing but, only being familiar with thermistors, thermocouples, PT100s, and similar *electronic* temperature sensors, I was expecting something like that (i.e. at least 2 wires), so only seeing a single metal tube totally confused me! ¹ Removing it twice per replaced item: once to get the details of the broken part that needed ordering, then later to actually replace it. The heating element was less than £10 from Amazon, so I was a bit doubtful about it, but it's been working fine for a few months already. Although with the amount of time it takes to replace the heating element on my oven, it'd *definitely* be better to buy the ~£30 version if this £10 part fails in short order!

Hi Clive. I'm heavy into antique and vintage refrigeration equipment. The ones with the saturated vapor capillary tube are very common with the old fridges. They depend on the sensing tip of the tube to be cooler than the body and diaphragm of the switch. The vapor pressure of the working fluid is what really gives these their accuracy. I've made several videos of rebuilding these when the sensing line gets broken. Depending on the temperature range the control was designed to work at, they used different working fluids. Some of them used sulphur dioxide; methyl chloride, Freon-12, isobutane, or propane. When rebuilding the fridge thermostats, if you can determine the temperature it is supposed to switch it, you can apply gas pressure and determine what pressure triggers the switch. With that information, you can consult pressure-temperature charts and find a suitable refrigerant gas to use for a working fluid. One of the original manufacturers of the vapor type thermostats is Ranco company. They have been in it for decades and have published quite a lot of repair info in the past decades. Ranco are still around and still very high quality. I think the second one you had in this video was a Ranco knock-off. Many of the ones I've rebuilt recently ended up with butane being the correct gas. Back in the old days, they referred to the ones with the expanding fluid (like the first one you worked on) as "hydraulic" thermostats. The ones with saturated vapor were called "gas" or "vapor" thermostats. I've been wanting to study and learn to repair the "hydraulic" type of controls. There are few who repair them when the capillary tube gets broken. The secret (as you said) is in the thermal expansion coefficient of the working fluid. Here's an isobutane thermostat getting repaired: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-WHv9Ut7guwE.html This one was originally methyl chloride, but I used 1,1,difluoroethane for it. It's almost like your second one you showed. In spite of being very similar, it's from back in the War of the Currents era in the States. Back when AC and DC were both competing technologies. Love the old stuff! Repair video: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-H7VQys1gPjk.html Thanks for the teardown video! I enjoyed it a lot. I hope you enjoy seeing my repair videos on these.

16:11 "This has little wings that fold round, little pantie-wings that fold round, for extra security when you're horse-riding." And those who watched ITV in the 90s may understand why this makes me think immediately of "UUUAAAAARRGH, BAAHDYFORM!"

"Panty rings for extra security while horse-riding." There's so much to unpack in that little sentence.

A couple of days ago I had to explain how thermostats like these work. I reckon I preformed not really bad, but now that Clive has emerged on topic, I can get back to the discussion again and demonstrate this video. Because it should help even more. Thank you, as always.

I always wondered how these thermostats worked. Thanks for the video it was very informative.

Those big bulbous knobs would look good on my steam punk electric guitar. 🎸 Especially going up to 110, it'll make it louder. 😉

The two with a vial are for sensing the room/box temperature, the last one is made to sense on the evaporator, and it matters a lot to get the right type for your application.

I've learned a new excuse: "I didn't drop it, those are calibration dents"

The 1st time I dealt with one of these I thought that tubing was an encapsulation for the sensor(that I thought was a thermocouple, thermal transistor, etc). I opened the vial and, to my huge surprise, it came out an oily fluid. I washed my hand several times, because I didn't know if that could be poisonous. It turns out that the oven was 100% electro-mechanical. I remember taking some time to understand what was going on, but eventually came out with the conclusion(that was correct). I love these mechanisms... they are like puzzles.

Fascinating! Thanks Big Clive! It's kind of wild that so little movement will control our appliances. The gas one seemed pretty simple until you delved into its inner workings. Such seemingly simple little pressed metal bits and springs creating something of fairly complex actuation. I think those engineers have earned their keep!

This was very helpful i was trying to figure this out after watching HVACR videos. A quick google was failing me but explained in the first 30 seconds. Sometimes the capillary connects to the system or to a bulb but either way the point of the capillary is to transfer the pressure with a small impact of the volume of the capillary.

Thermodynamics I love it! Fan speed, Condenser temperature, evaporator temperature. And room ambient temperature all play a role

@15:28 the knob does not rise and fall to the case, the red rotating wedge increases or decreases the force on the diaphragm lever changing its position and/or resistance to movement creating a manually variable switch on/off state. @20:31, you got it!

almost a half hour of big c pulling his knob, thats hot!!!

Over the years I've changed lots of these - ovens, water boilers, water and oil filled heaters. I've never seen any fault different from spring relaxation of the switch mechanism caused by faulty contacts overheating it. Expanding sensor-actuator part might be a dark sciense for a lazy person, but the spring mechanism of the switch is a real engineering voodoo. Changing heater thermostats in my very old apartment, however, became a very difficult task - they were made in England, but apparently no more so getting new one is a quest of walking through all spare parts shops without websites in criptic parts of the town.

Big Clive for the save! Helped me confirm my freezer thermostat was working perfectly

You are practical as well as theoretical, very good sir

You do it like Dave. You take it apaat... Awesome analysis of the thermostats at hand.

The last thermostat you took apart is indeed for a freezer. My Arctic King 5 cubit foot chest freezer has the exact same thermostat. It's so cheaply made that over time, the small vibrations of the compressor cause the set screw to turn, which causes the freezer to to stop getting as cold after a few years. Most people just throw the whole unit away, but it can be fixed by simply adjusting the set screw on the side. Mine is especially bad and has had to be adjusted twice in 3 years. Meanwhile, the freezer on my fridge from the 1970s has been holding 0°F for 40 years and hasn't missed a beat. It's sad how cheaply things are made now.

On the freezer thermostats I’ve seen that are mounted inside, they have all been filled with some type of refrigerant. Interesting to see one that is just oil. I believe you can tell the difference by not only the diaphragm but also the expansion bulb. The oil ones appear to have a much larger surface area for the expansion bulb whereas the ones with a refrigerant have extremely small, almost non-existent expansion bulbs. Probably due to the thermal sensitivity of refrigerants.

Love all your content Clive, please don't ever stop, I could watch and listen to you explain just about anything. (Loved your hot dog video, watched it from start to finish, were they friends , family or both?)

The last thermostat you showed is a typical fridge variety, it is nearly always mounted inside the fridge, at the back right next to the evaporator. So the whole of the unit is essentially in the conditioned space.

The capillary only thermostat is designed to be mounted inside the conditioned space (frig or freezer) and as you said uses the tube and bellows for temperature sensing. The screw and attached spring assembly make up the span adjustment - the difference in temperature between on and off - and the other screw is the calibration adjustment.

A delightful exploration! In our scrap area at work I'm always finding rolls of copper capillary tubing that have been cut. Always wanting to find a use other than a magnetic loop antenna. LOL

movement of the drum has to be slight as it is magnified by the armature due to its closeness to the pivot

These "hydraulic" thermostats had to be calbrated for use in high altitudes. Also if you can find an old Cutler-Hammer thermostat, they not only have a method of calibration but separate screws for adjusting the cut-in and cut-out.

The third type (without bulb but with big bellow diaphram) is used in 5 gallon bottled water dispensers which usually have two thermostats. One for chilling side of dispenser and second for heating side so you can get hot water for tea/coffee or cold water for drinking. The capillary tube of each is wrapped around respective small insulated heated or chilled water holding tanks. Temperature setting shaft for chilled water tank is either inside dispenser case (for factory adjustment only) or extends outside but without any knob or dial scale for user adjustment.

I think the "gas" would be something like Freon, and it's transition from liquid to gas depends on the temperature and pressure (the state transition giving much more decisive action). Plus the two adjustments are to set the amount of Hysteresis as well as the Temperature.

The volume of the bellows/diaphram is much larger than the capiliary and is therefore gas operated, since the diaphram movement is large enough to operate a microswitch. The refrigerant in the system is presurised and boils at a certain pressure (set by the setpoint dial spring pressire on the diaphram) thus increasing it's volume and operating the microswitch.

Dead simple (and remarkably reliable) mechanism! Able to (reliably) switch decent current too, so an example of excellent (although nowadays decidedly "legacy") engineering. As you say, almost "everything" these days will be electronically controlled (pre-programmed PID controllers) which (though offering far closer control ranges) do seem to be far less reliable, despite "no moving parts inside".

i worked in a valve manufacturer several years ago an i had the job of putting thermal switches on the valves with electronics an comtrolers valve positioners 'most' of the thermostats i had to work with it was a highly refined mineral oil as it wont freeze an has a high boiling vapor point

Love your channel! You're accent sounds just like Scott Manley of KSP fame!

Others have mentioned the last one used in fridges, 'Off and then numbers', no specific temperature setting. I like a cold, cold fridge and on mine, the two screws going into the springs I've tweaked before now to set the low and high temp it cycles at, making it narrower hysteresis band than stock. (Usual disclaimer in case yours wasn't like mine. 😉)

Might be a nice contrast to take apart one of those Chinese electronic thermostats (such as the ever-popular Willhay WH360, which seems to be everywhere on the "usual sites"!) They work pretty well, seem reliable enough (ours have lasted 10+ years with zero problems), and have enough added functionality to be of use in heating and cooling applications.

the small tube one uses vapor. the liquid-vapor change doesn't need much contact area, and the pressure inside changes the temperature at which it condenses/evaporates.

Remember the old Teddington QR stats, they used sulphur dioxide as the sensing gas!

The unit you disassembled after 13:00 looks almost _exactly_ like the thermostat used in my 1986 Suzuki Samurai's A/C system. Mine only has 2 contacts, though.

Clive, I also see this style of thermostat in Boilers for coffee and other dispensing equipment.

A single 555 or an op-amp can also be used to make a fridge thermostat (if you don't have a microcontroller based one). The only trouble is that a 3...5 minutes pause should be implemented between turn-on and turn-off.

The MSDS I found for one remote bulb thermostat said it contained toluene. A Honeywell datasheet for a different unit said the bulb fill could be toluene or silicone oil. These both appeared to be for HVAC applications.

at 2:55 that type is common in many refrigeration uses, the other mistake is not winding the excess sense tube into a coil and making sure to place it away from the refrigerant tubing (suction or pressure) with will skew it greatly, especially in the sense of a deli display case (learned the hard way)

You really got me shouting at my screen this time 😁 The gassy one might have been liquid within it's operating temperature range... And the more narrow the diaphragm, the bigger the travel for a given expansion of the medium used.

Love the commentary brother 😁

its common for the capillary type to be embedded in the evaporator coil to sense to temperatures of the coil itself, another reason why the temperature range is so low. the contacts that stay closed all the time are for your evaporator fan motor to run 100% of the time, the other contacts switch your compressor and condenser fan on. from what i've been told by industry, most of these liquids are a refrigerant of sorts.

Still in common use all of this. The square one is a simmer stat used for catering trolleys. Some say there temperature range on the side.

The last one with the coppery diaphragm is almost certainly out of a mini fridge. I had to replace one just the other day. it has the same diaphragm, three terminals, and the gray plastic section attached to the aluminum section. the form factor appears to be identical. although the guts are slightly different.

Fantastically entertaining. I've irretrievably broken SO many things , over the years, by taking them apart to " see how it works" :D

I have disassembled multiple water heater thermostats years ago, and all of them contained ether, with Li-ion electrolyte smell and instant evaporation.

Hey Mr. Clive! Thanks for your great videos, really like them 110% and watching almost every one - one sentence - you are a genius at your filming and knowledge about almost everything that comes to your bench... Being a handyman myself, i only would like you to return to your "dark and dodgy" videos about some strange invention that you came across on ebay or your old projects that you made. If you could "return" to some older stuff, i personally would be very happy :) Thanks and best regards, Zlatko

The two screws on the front are for calibration - they set the depth of the stem (the first thermostat).

you're good at making stuff up as you go :0

It is a freezer stat the reason for the the extra terminal is it brings on a red warning light about 10 degrees above the set temperature so you can see there might be a problem. The capillary only need about 80mm in the cold area to work as the pressure will change even if only a small amount is cold area.

the capillary is usually filled with refrigerant r22 or butane

While repairing appliances I noticed that when some of these are broken the contents of the probes sometimes ignite quite spectacularly when exposed to air, shame you didn't get one like that, I always found it amusing.

The Opening Things Up Channel.

Many freezers have a fast freezing mode that runs the compressor continuously when freezing large amounts of fresh produce.

I think that liquid is called a refrigerant it could be HFC example R134a. Thanks Sir

Hi Clive, The small thermostat is full with ether!

Commonly use toluene as the working fluid in most of the displacement type of thermostats.

the 3rd contact is just a line jumper that sends 120v to board for the "fast cool" feature. All it does is bypass the thermostat and power the unit to start cooling when you hit the button

we use silicon oil or glycerine as transmission liquid in diaphragm seals :)

14:30 I’m still working on my carefulness lol. Always have little scrapes, cuts on my fingers from tinkering.

Ugh... I've a similar kind of thermostat in my HVAC heat pump, line voltage mechanical thermostat... its temperature range fluctuates so it's terrible to manage, getting it replaced with a digital thermostat this spring :)

Thank you Sir Big Clive ! ;)

In the stream tonight, could you maybe explain how a mercury rectifier actually makes current dc? (and he never did)

Clive, have you seen the new battery powered 2x LED COB lightswitch from Poundland? It has a slide potentiometer connected to minimal circutry to change the brightness, it has an integrated switch mechanism to cut power. Quite well designed actually, but disappointing the COB LEDs are smaller and have 8 diodes each on a single board instead of 10 diodes on individual boards like the previous one (I bought them for the components)

"A chap called Nowis"

Aww you didn't set fire to the oil! It burns really well. The last 2 I cut open the oil smelled a lot like standard 28 second heating oil, and it burned quite nicely once warmed. (well it burned with a lot of smoke anyway...)

the few Ive broken open had mineral oil in them, also some contain alcohol.

Could that liquid be mineral oil used in heat transfer in power transformers

'it could be some oil or...." me waiting for him to taste it....

the freezer stat has 2 temps settings 1 is adjustable to switch at -15 if temp rises above this it will light a red neon or a buzzer the other is to compressor at -18 to -28

TIL! I guess I assumed they worked off of electronics like using a thermistor or something to that effect. This makes more sense for a low-cost thermostat, like in a mini-fridge

I love this video he wasn’t slurping a drink or masticating

I think the first one is for fridges mostly neofrost fridges and the 2nd one is for Windows ac because I've tried to use the 2nd one in some neofrost fridges and failed to perform accordingly.

Could you explain the extension spring at 20:08? I turned mine whilst trying to calibrate and I don’t know where it should be😮

Quite a lot of domestic freezers have that bulb in the cabinet, so the mystery oil would have to be food safe. Your fingers aren't likely to rot off from exposure to it.

Possibly Glycerin as the oily substance?

what a lively thread, i just had fridge/freezer re-gassed, after that it was running continuously, fridge down to 0.6C° and ice build up on suction pipe at compressor; figure thermostat must be faulty, replaced it with identical new WDF28C-L-EX, no change, it either still runs too cold, or after turning one of these small screws, the compressor cuts out, but doesn't come back on; also, my thermostat has got 3 tiny screws, one on the front (knob side) and sunk in, another on the side, which made the compressor cut out when turning and a third even smaller and sunk in brass screw on the backside; i can't find any information what the actual functions of all 3 screws are, any ideas here ? thank you

who else thought it was from a person called nomis. lol love the videos clive keem em comming.

the second one is for a heating and cooling window unit.

The smaller shorter capillary tubes thermostat requires the capillary tube be inserted in traditionally an evaporator coil. A tube is installed in the coil to receive capillary tube. Edit: this one would be considered Medium Temp.

That part number is for a GE fridge thermostat

Maybe the first one has hydraulic silicon oil in it. I'm guessing it might be more likely that it works by heat affecting the pressure of a vacuum in the vial that squeezes the silicon oil down the capillary tube

I've seen things of this sort also used to regulate the temperature of an oven...