Fixing a completely dead Nest thermostat heat link

.Spoiler - it wasn't a capacitor.
If attempting a repair like this then take extra care to ensure the power is off to the PCB. It has a lot of exposed live tracks on it.
Do you remember when thermostats were cheap, simple and lasted for over 30 years? Welcome to the future where they are expensive, crammed with electronics and may not last a tenth of that.
I think this one managed to scrape by its one year warranty period before ceasing to sense.
I would categorise my test-bodge as a temporary measure to identify the fault. It would be better to get the proper component, although it's not an easy one to desolder. It may require more aggressive heat pen use and probably some careful masking with Kapton tape to protect adjacent components.
In use the unit seems to run pretty cool. The two hottest components visible to the thermal camera were the PSU diode and the PSU primary side MOSFET, and neither of them was particularly hot.
If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:-
www.bigclive.com/coffee.htm
This also keeps the channel independent of KZbin's advertising algorithms allowing it to be a bit more dangerous and naughty.
#ElectronicsCreators

[@davidcoghill8612]

It's not just a case of the hardware physically failing, you also have to contend with the fact that often these things only work as long as the manufacturer supports them and at any point they can choose to brick it.

[@pibgorn9513]

Indeed. Two companies that are on my naughty list are "Hive" (IoT) and "Reciva" (internet radios).

[@volactic8495]

My rule for companies these days is that they are guilty until proven innocent (such as providing the software in the box on a physical format)

[@JanicekTrnecka]

Another failure mode -> bricking them by errorneous firmware update. AFAIK it has happened with some nest devices already.

[@Dreddy72]

@@pibgorn9513 im happy i decided the hive lights were too expensive and didnt buy any more after recieveing a gift starter set. on the plus side, at least the bulbs still function as basic bulbs and dont flash till they connect..

[@cheyannei5983]

@Christopher Grant There are programmable thermostats that get you 100% of the heating/cooling benefit (not having to work when the building is unoccupied or special rules at night, etc) that also cost less than these Nest units. We got ours from Braeburn and we've been happy with them. But if you have a mercury switch, it's likely the zone control board and equipment is old, too. Not really a worry, but the new equipment really has been making strides in efficiency; a heat pump will efficiently heat your house till it's near freezing, using many times less energy than your normal heater or furnace.

[@digitalsparky]

"Internet of sparks" ... shockingly good wifi? :P teehee

[@theelmonk]

The worst weakness is that it's dependent on the manufacturer finding it profitable enough to keep the servers going

[@bigclivedotcom]

This is where a geek-run independent server or new firmware wins.

[@james-5560]

True, unlikely with Nest though as it's Google and they own their own cloud platform, this likely runs on serverless architecture with hundreds of other applications also running on it. We're taking about simple JSON api calls and virtually no bandwidth costs.

[@howard81]

I had exactly that with my alarm system (iSmart Alarm). £400 on parts only for them to go down the pan and switch the servers off 18 months later!

[@MentalD-Fox]

The 3rd Gen can be set up without Wi-Fi so you can use it offline no worries.

[@katrinabryce]

@@james-5560 Google have a really bad track record for discontinuing old products. They had a previous line of smart-home products that the discontinued when Nest came out.

[@MladenMijatov]

I love these repair videos. They clearly show what kind of analysis should be made and how to solve the issue.

[@LukaMandic31]

Mr. Mijatov, are you from the Balkans?

[@MladenMijatov]

@@LukaMandic31 da, jesam. :D

[@BillAnt]

He should have used the infrared FLIR in the beginning which probably would have revealed the shorted diode by displaying it as heat due to the high current drop. Just a thought....

[@Strider9655]

@@BillAnt This is not always the case, depending on the power supply, might have a short circuit protection built in, tries to start, detects a short, shuts down. I've spent hours chasing faults like that on large PCBs, where the fault could be a short circuit SMD ceramic capacitor, of which there are 100+ in parallel all over the PCB. So what I do is isolate the power supply, solder wires to the faulty supply rail and connect it to a 30A power supply at the normal supply voltage, THEN use a FLIR, or if the boss won't buy one, spray IPA all over the PCB to see which area it evaporates from the quickest ;)

[@PhoneVidoes]

Brilliant job, yet again a 10p component causes £££'s repair bill for the average consumer. Reminds me when I re-populated our fridge freezer control board with fresh caps, new board was £450 ! ! full set of caps costing about a £5 and an hour replacing them and the fridge freezer went on for another 7yrs before failing seals which I couldnt replace teminated its 20+years service.

[@Tokaisho1]

Oh wow, at that price you're definitely better replacing the fridge freezer completely if not repairable like you did here

[@thebrowns5337]

@@Tokaisho1 charging more for a new board than an entire new product should be made illegal. It's nonsense like this that keeps landfills growing...with all the health and environmental damagd they cause.

[@jasonbrindamour903]

I had a 4 year old furnace board go bad, acting strange. Visual inspection show a electro cap bulging next to the control chip. Replaced it without even taking the board out. < $1.00. worked for 7 more years before another board needed

[@Francois_Dupont]

a control board for a freezer??? a commercial one? because with a normal fridge i think there is only the starting cap for the motor and a simple thermal switch and capilary to trigger each cycle.

[@hadireg]

that's how things should be!

[@paulstuhlfelder9819]

Mine failed recently, there’s a guy on eBay who repairs them for £30- a new one is over £200 as you have to buy the thermostat as well 😡😡. There is a quick test he told me to do before sending it away, connect the micro usb cable, if it lights up he said he would be able to repair it, which he did, and it was the diode, looks like a very common fault on these units.

[@leww]

My Heat-link failed the same as this just before Christmas and I messaged nest support, they’re aware of it and next day delivered me a new one at no cost, and even offered to cover any costs of ‘professional’ installation. I didn’t even buy the thermostat from them I got it off eBay so I can’t complain at all👍🏼

[@paulstuhlfelder9819]

@@leww couldn’t find any help on the internet at all in the UK

[@leww]

@@paulstuhlfelder9819 Sorry to hear, if you’re still stuck you contact nest support via live chat, they try and connect to your device and ask you to do some basic checks for them, then if no luck getting it working they’ll overnight you one from Ireland which is what happened with me last week 👍🏼 There’s an extended warranty on them in certain circumstances.

[@paulstuhlfelder9819]

@@leww I paid £200 for a new set, got the other repaired on eBay for £30, so now I have a spare for when something inevitably fails again 😊

[@paulstuhlfelder9819]

@@leww thanks Lee for all your help, much appreciated

[@johnjones4825]

After having a dead computer motherboard for 5 months, I decided to try a repair. Found 3 caps slightly swollen. In our little town there is no supplier of discrete components, so I went to a rather dodgy little shop that "repairs" computers. I got one cap of the same rating (1800uF, 6.3v) and 2 others of 2200uF (all 2nd hand). Due to my lack of desoldering braid, I had to make long jumpers to bring to the "wrong" side of the board and have the new caps hanging in the breeze. What a pleasure, I'm typing on that (12 year old) PC now, 3 weeks and so far so good!

[@skylined5534]

Nice fix! May she work for a many more years!

[@tin2001]

Amateur tip: a straightened out paper clip pressed onto/down the hole while heating will create a large enough hole in the solder to get the new components in. If the paperclip is stainless steel, it'll slip straight back out. If it sticks, reheat and wiggle it in circles while it cools to stop it clinging. I did that on an Xbox board to install an early mod chip for a friend.

[@stepheneyles2198]

Great to see you're back home Clive, and nice to see that scorched desk again! Nice fix on this one; gives us courage to investigate rather than chuck stuff out and buy a new one! :-))

[@soberhippie]

I always investigate. I never was able to fix anything or reach any conclusions, but I always _investigate_

[@TheCod3r]

Always love to see repair content from you Clive. Keep 'em coming

[@oldfatbastad6053]

I prefer the Cooking With Clive episodes 😄

[@punksci6879]

Pro tip you can use two soldering irons to lift a single component like that in a densely packed area. I've had to do that for replacing a load of boards after a bad batch of SMT caps.

[@matthewmiller6068]

Look into some cheap SMD soldering irons that are like 2x30 Watt ones with a spring pivot. I got one for about 30 bucks it was a game changer for SMD desoldering

[@chrissavage5966]

Love the 'mains to death' lead :) Forgot to say before, your bench makes me feel at home. I had a hardboard topped workbench in my workplace where I spent probably the best part of 25 years at the same bench. I even managed to obtain one of it's brothers when I retired (there had been 8 of them specially made and as the years passed, less and less were needed). Mine too has a few witness marks :) Probably the least pleasant witness mark was perpetrated by a French student we had on work experience with us one time. He had a bit of a night out then proceeded to barf on my bench. I was off shift that day and my colleagues did a pretty good job of cleaning up the mess. Happy days....

[@Francois_Dupont]

they use a strange glue. one time a single drop of cooking oil (i think) fell on mine and it was like acid deteriorating the wood. i have a hole at that spot now.

[@roberthuntley1090]

That is a Heat Link unit, necessary on UK systems to interface the low voltage switching in the thermostat to the 240V switching traditionally used in our heating systems. Just for information, the T1 & T2 terminals supply a nominal 12 volt DC supply which can be fed down the old thermostat wires to supply power to the Nest thermostat, charge its battery etc. At the thermostat end of the cable it doesn't matter which way round the cables are connected, so there must be a bridge rectifier in the stat. I think that there may be a small data stream as well, because pairing of the two units is automatic when connected in this manner. NB - The other configuration would be to power the Nest using a USB power supply and cable, when it is mounted on a desk top stand. I've lost my instructions, but can recall the need for a pairing procedure if you do this. In both cases, the two units connect wirelessly to pass heating commands from the stat to this unit.. My Nest Mk2 worked faultlessly from 2014 until it was recently removed (a new boiler came with Hive as a package deal). That model couldn't control the hot water, so is presumably simpler inside with only one switching relay to pack into the box. I believe yours is a Mk 3.

[@muh1h1]

I used to work for a local Cable ISP and they used 60V AC to 24V DC Switchmode PSUs in every single one of their outdoor Cable Cabinets. While they were the leading cause of total failures, they were surprisingly robust! Most of them were more then 30 years old before they died, running 24/7. Most of them failed when it got really cold or during Thunderstorms. They also liked to not turn on after power outages, probably because they got too cold. We tried repairing them once when we could not get enough of them during last extremely cold winter, and it was always either the fuse that failed (totally dead) or the Caps that aged (No cold start).

[@brianleeper5737]

Can't imagine any cable company running equipment like that for 30 years. Most have switched over to 90V powering, and the switchmode power supplies are either in node, amplifier, or line extender chassis, which were upgraded (or added) as they went from 300MHz to 450MHz to 550MHz to 750MHz to 860MHz to 1GHZ bandwidth.

[@theelmonk]

I got a bunch of 24V (240 in) power supplies from ebay. They're good quality ones originally used on point-of-sale equipment. They all seem to have suffered from failed fans.

[@Omensan]

9º? You keep your work desk at 9º (48ºF)?!? No wonder you're always in heavy flannels! Great fix! I love the Nest hardware; shame they were bought by Google. By example, Google just announced the discontinuation of the OnHub series of routers which require the Google Home app to manage and operate. Perfectly good devices will simply die when Google switches the ability to mange them off. The Nest home thermostats and controls will hopefully have a longer lifecycle, but perhaps the bean counters will spot this opportunity to prematurely deprecate perfectly good gear too.

[@stepheneyles2198]

He's Scottish; they keep themselves warm from inside!! :-D

[@bigclivedotcom]

I prefer a cool house. I use dehumidifiers to keep it dry.

[@quarteratom]

That's so awesome, you can fix anything. You just test what component broke, and replace it from your endless collection of electronic parts. That's a great skill to have, I probably could have repaired some of my broken electronics, if I knew more. You are a magician.

[@robinwells8879]

Don’t know you have ever watched STS Telecom and his skills and steady hands? Probably because of of the power of the algorithm you have!

[@jimmuehlberg2153]

I admire the dexterity of holding the diode and solder simultaneously with the same hand at 12:05!

[@Broken_Yugo]

My parent's house still has the ca 1960 Honeywell T87 mercury thermostat, original to the oil furnace installation, works fine, zero trouble. Worked even better once I figured out nobody bothered to adjust the anticipator setting after the furnace was updated to an electronically controlled burner with a much lower thermostat current.

[@MickeyD2012]

I love quality engineering.

[@BloodAsp]

"Do you remember when thermostats were cheap, simple and lasted for over 30 years?" HA, my parents house still have the same bimetallic strip coil based thermostat since the house was constructed! Thanks for the thought, if they ever get rid of it, I may yoink it off of the wall.

[@casemodder89]

the nest !?

[@Francois_Dupont]

funny story my father installed one of the new electronic thermostat for a fan heater in the bathroom. the room is so small the thermostat would turn ON/OFF maybe 300time a day. after a week it has started smoking and stopped working. i just told him to buy the "old one" and it is now working very well. i doesnt even cycle all that much since the mechanical trigger inside is quite slow.

[@Acecool]

@@Francois_Dupont Yeah, you definitely do not want them cycling like that. Turning something like a computer on / off a lot is quite damaging.

[@christianelzey9703]

My parents' house still has one of the round Honeywell mercury switch thermostats every single house built in the mid 1900s in the USA has/had. It's got to be 60 years old and still works just fine.

[@Francois_Dupont]

@@Acecool i dont know why they didnt program a simple delay or something.

[@christopherwhitehead4042]

Just wanted to say a big thank you! Had this exact same issue today on a 3yr old Nest and as a regular follower assumed it was a capacitor. Never would have known about the diode without this. You've just saved me £150!!

[@William_Hada]

Good job on the fix! I especially like these diagnosis/repair videos. I love to see and learn from your diagnosis strategy and techniques

[@Birchall88]

Just checked the dead one I had lying around, and it is the same diode that has died on mine. Thanks.

[@dickcheesehead9714]

Thanks for the content and your reassuring calming personality. I always have been intrigued in the magic of micro-electronics. I never got into it and still I don't understand half of the things that are on a PCB. It's very fun watching you (read: oh holy expert) do the screwing around. Cheers, mate!

[@paulmear8353]

Hi Clive, I had the same problem with my nest. It is a design or manufacturing fault. Nest replaced mine out of warranty for free, sent me a replacement by 24hr courier once I got through their customer service triage. Happy days. P.s it still worked when powered via the micro usb socket.

[@Double_Vision]

Identical issue here. Google replaced the whole unit as well. After speaking with the boiler man there was apparently a rash of Nest failures that were all identical.

[@rompdude]

Sounds like it was the power supply if that's the case. I bet the USB directly connects to the low voltage control side. However, strange the relays worked as they are 12v

[@insight1014]

I had exactly same fault. 3 Year old unit contacted Nest/Google support on Friday evening described fault and on Sunday received new unit with email stating they would cover refitting cost with nest pro installer.

[@majintheport]

Hi Clive, another duplicate, happened to me Wednesday before Christmas and Google managed to send me a free replacement, out of warranty, within 48hrs. Quite a refreshing support response from Google, I expected a battle :)

[@Hybridesque]

Had the same happen after a power cut and resumption of power.

[@WadeWomersley]

We've got a Nest thermostat, had it years over a really old boiler and a new modern combi one. For the most part it has been reliable, the only issue is sometimes the remote control unit says "cannot control this unit" then it fixes itself if you just hit continue and let it fix itself. I installed the original one to the old boiler having never done it before using their guide + KZbin, not that difficult if you have faith in yourself and understand the basics. The hardest part is (for old boilers) deciphering the connections when you can't even find a manual anymore. The reason I love it so much is the heatlink (the thing you have here) and the remote control unit both have thermometers in them so, if they're in separate rooms, you get a really accurate temperature control in the house that's all taken care of for you. It actually did result in saving us money pretty quickly!

[@simonastro]

despite my appalling soldering, you've just saved me £70. many thanks indeed

[@stuc.6592]

Point of order Mr Clive, that's the control centre, not the thermostat. I've had two fail within the warranty period and Nest replaced them without any argument. The later ones seem to be much more reliable.

[@shaples]

Very true, and interestingly enough, they’re not included with thermostats in America! Seems like a solely European affair

[@AJB1]

@@shaples yes. As I understand it, the US doesn't use mains voltage signals for the logic and switching to drive heating systems, unlike European, or at least UK, heating. So the US nest thermostat unit drives the heating system directly with low voltage control signals, whilst we get that box to translate the thermostat's wishes into mains-switching relay openings and closures. It also provides the power to the thermostat unit.

[@brianleeper5737]

@@AJB1 In the US you'd only find line/mains voltage thermostats used with electric baseboard heaters. Everything else is 24V.

[@JaenEngineering]

A good trick for protecting nearby components when using a hot air gun is to cover them with folded aluminium foil held in place with kapton tape.

[@AnT508]

Thanks! I'll try that next time :)

[@drkastenbrot]

kapton tape alone does the trick

[@tomsixsix]

I've found Kapton itself fine. Get a large strip of Kapton or layer several consecutive pieces then use a knife to cut around the part you want to remove. The Kapton will survive long enough to protect the components covered by it.

[@chestermartin2356]

They used kapton for the sun shield on the James Webb space telescope too 😀

[@skylined5534]

I'd definitely go with the tape only aswell incase something gets shorted and damaged by the foil bridging things. That said, the foil thing is good to protect the odd individual component that might be overly sensitive to heat.

[@danyf3116]

BIG Clive: " ...internet of sparks!" ELECTROBOOM: Am I being summoned?

[@keithlambell1970]

Great work. Interesting to see the output side diode fault in another product.

[@TopEndSpoonie]

Thanks for that Clive. Straight back to work after getting Covid and Christmas. What a trooper!

[@jonnyduncan7056]

I'm a Sparky and installed three or four of these and had to go back to all of my customers after the Heatlinks and one main Nezt 3rd gen actually 'thermostat'/transmitte (wifi chip) failed). Google, now owners are helpful and cover them even if bought over a year ago, but it still takes 2 weeks getting a replacement here in UK! It's a shame as the customers are left without heating and hot water for that time unless, we re-fit the old hard wired units. At home, I've left my.old back plate, in circuit, so I can fit the old 2 channel programmer/timer.in case . Totally agree ref. IoT Clive. We have a chap locally whose whole house is 'Smart' until he looses Internet and Wi-Fi.. Keep up the brilliant work

[@Graham_Shaw]

Another great video Clive! My NEST learning thermostat (same as this one) failed after around 18 months. Fault was a little different on mine, it still powered up from mains but could not talk to the remote thermostat. I traced the fault to a short across one of the output side capacitors, but by which point I'd already submitted an RMA form and got a replacement sent out, but they insisted I return the faulty unit to the Czech Repuplic to then be more likely chucked in a bin 😞. Things worthy of note:- Different brand of relays, Mine were black, and the two output caps on mine where the same type and brand of electrolytic caps, but obviously different uF values. I wish I'd taken pics!!

[@ronniepirtlejr2606]

I had a surface mount diode burn up on my buck power supply about 10 days after I bought it. I thought maybe I had exceeded the maximum voltage input. No I was about 10 volts under. I ordered some new SR5100 they came as through hole components. I soldered one to the board & it's been going strong for 4+ years now. I believe the through-hole equivalent diodes are much more robust than their surface mount counterparts. Good job big Clive. I enjoy watching your investigative work on electronics!👍🇺🇸

[@drkastenbrot]

through hole has a higher rate of failure due to being more susceptible to vibration. it really depends on the application and environment.

[@reacey]

@@drkastenbrot yeh I always thought that the smaller you go with components, the more reliable they generally get

[@bigclivedotcom]

The through hole components are more resilient to thermal stresses due to expansion and contraction due to the slight give in their leads.

[@ronniepirtlejr2606]

I agree with you all for most of the SMD parts. I'm just saying that the diodes seem to burn in half alot with SMD. even when the device is still new.

[@Broken_Yugo]

@@ronniepirtlejr2606 I wonder if that's because they're SMD, or because shit has gotten that much more "value engineered" since SMD took over.

[@neilmcclean9314]

Brilliant video again big guy, I've been installing these for a few years now and of late had quite a few customers contact me with a "dead" Heatlink.. ironically they all appear to be within their warranty period...Nest have been very proactive in replacing these rapidly.... interesting to see it opened up with the circuit broken down and an explanation... excellent watch as always 👍

[@ooglek]

Well done! I love to watch you diagnose and repair common electronics. Keep it up!

[@highpath4776]

You need some T Shirt merchendise - "There's More Screws' , 'Did Some Preliminary Probing' , ' Just Squirt Some Flux Over It' , 'It Sticks Up A Bit'

[@mattfleming86]

I love repair/diagnostic videos!! Thanks Clive

[@jacobsandell9677]

Amazing - my nest display failed after 11 months and was changed under guarantee. Th Heat link failed after 14 months but following this video I fixed it having bought the diodes (UF4003-E3) from RS for about 10 pounds including delivery. I used a soldering iron and stanley knife to flick off the defective diode which came off in pieces. Thank you Clive!

[@tinytonymaloney7832]

How lovely to see a good old fashioned wholesome BC repair video. 👍👍👍

[@Leonvolt28]

Your hands are pure magic to me. Holding the tin and the component in one hand while soldering it on with the other.

[@azz2693]

So glad I subscribed to BigClive a while ago, watched this video when it was released and had an interest as I also have one of these nest system. A few days ago mine failed after a power cut and came straight back to this video to test mine. Same fault. Lots of looking online and found that the PDS3100-13 (RS 751-4654) is the same as the one on the boards. Got them delivered today and now have my heating back again. Thank you so much Clive, keep up the great work 👍👍

[@brendanlee2255]

Spot on! PDS3100-13 is perfect fit. Just replaced mine to fix this issue. All working again. Thanks for the tip.

[@beardedlion]

Thank you so much! I woke up to a cold home, my heat link had failed. Then I remembered that I had watched this video when it came out. So I got my multimeter out, the failure and shorts matched the video! I've replaced the diode and it is working perfectly! Thanks again, keep up the good work!

[@bigclivedotcom]

Thanks. Glad you got it sorted.

[@BobMuir100]

Clive mate that was 100% brilliant for me and whilst I doubt I will ever use it, it was so good to watch mate.....thanks Kindest Bob England

[@BobMuir100]

Thanks Clive, hope u r keeping OK?

[@fromfin90]

Ah internet of things, future landfill when apps stop working

[@zh84]

The business of killing the applications - and the equipment - by turning off the servers is outrageous.

[@stepheneyles2198]

@@zh84 Had to buy a new WiFi SD Card for my camera as the company released a new version and ended support for the old one... Forced redundancy. Didn't buy from them again, so I felt a bit better!

[@jameszeng4869]

Great video, today my Nest got the exact same problem after two years of usage. I followed your instructions replaced the diode, it works like a charm. The only thing I did differently is, I used FR107, instead of uf4003. I hope it won't bring any problem in the future. But at least for today, until now, it is still working fine!

[@Gledster]

A comment from the future. James, is your Nest still working after your repair?

[@hadireg]

nice peek into this Nest... also very satisfying when the culprit is a usual suspect not the tricky rabbit to track down endlessly :) Thanks for sharing mate!

[@hullinstruments]

Heck yeah. Been waiting on some big Clive general troubleshooting content!👍👍👍👍👍👍👍👍 more please😁🤘

[@andrewchesney]

I'd wish I had seen this last year - it possibly coulf have saved me circa £120 - GREAT VIDEO

[@serenity1378]

The Nest thermostat I have was actually a drop in replacement, I did buy the model specifically listed as user friendly/installable. It had a "for dummies" guide on identifying how your boiler received the on/off signal based on the existing wires, and where to wire those up to the Nest to make it work. If you have a compatible boiler - mine I think just has "power on this wire means turn on, no power means turn off" - and you don't mind taking your time, it's not that hard to install. Of course all the other downsides you mentioned - failure rate, security, etc - still exist. I run an entirely separate wifi for my "smart" devices so they can't see any of my actual private stuff. It's important when we're having the conversations about the downsides that we recognize the benefits too. Not just for laziness or, nerdiness, it's a sad fact that disabled people like myself can find a great help with smart devices - sad because we have to trade our privacy and security for it in the world we live in right now.

[@lordjamestaylor2268]

Can't thank you enough for this video, I've had one of these on my desk for a while now and now I get to fix it.

[@patomahony9747]

Nice to see you back at your regular bench. Loved you initial comment that’s now added to some of your others “Hackers Paradise”

[@OrbiterElectronics]

Great job Clive 👍

[@SodaAnt7]

Here in the US I’ve never seen a thermostat powered by mains voltage. In every house I’ve owned or lived in the thermostat either wasn’t powered at all (it used a bi-metallic strip), was powered by batteries (usually 2 AA or a 9V), or used the 24V AC provided by the heating/cooling system.

[@Anthony-ym6iz]

Love your channel Big C - have a great new year big man!

[@Caluma122]

Great video Clive! Really enjoyed this. Such skill on the repair whilst also doing a video.

[@stanislavmarszalek8721]

Hi Clive, great fix! The same happened to me after 2,5 years of usage and guess what, your fix with diode repairs thermostat and it is working like a charm now. I own you a beer at least 🙂

[@philmerrifield1163]

Glad to see you're back at the usual bench Clive, I actually made a point to a friend whom had an iot washing machine and hacked it using my phone in less than a minute

[@Chris.Wiley.]

Good to have you back at your regular bench.

[@brianwharf4916]

Love your fix videos. Thanks Big Clive!

[@krisdevoecht]

My second nest thermostate repaired by your video! Thanks for the info.

[@johnfrancismartin8989]

Clive I found your troubleshooting very helpful it convinced me that this fix wasn't for me. I'm off to Screwfix in the morning THANKS !!

[@bigclivedotcom]

You may find that it is replaced under warranty even if past the warranty period.

[@user-zy2kt6wc6g]

Thank you verry much. The UF4003 did the job. Great tutorial. My nest heatlink v3 was 2 years and 3 months old when quit working.

[@colingamble2959]

Hi just watched video and repaired my nest relay in exactly the same way, excellent result.

[@jdpti]

This controller has a power connection for the room stat which has a screen and rechargeable batteries inside. So a fault further down the line from the controller could be the reason this diode having failed.

[@dandymon]

Agree. That diode would have heated up a lot more when powering a nest thermostat and charging the internal battery up. It’s likely a blackout could have caused the batteries in the unit to drain, just putting a little too much strain on the diode when the power came back on.

[@dandymon]

Add a dash of thermal runaway..!

[@jasonkuehl639]

All is right with the world, Clive is back at his workbench! 😃😃

[@klaust.2769]

Nice work! I hate these kinds of SMD components. Recently I tried to repair a laptop mainboard. One of these modern "smart MOSFETS" in a SOT-873 package had failed. I couldn't desolder it with my hot air soldering station. It was impossible to get enough heat into the component to desolder it without destroying other things. Finally I destroyed the mainboard with this attempt.

[@simondhancock7780]

Thanks Clive - spurred me on to fixing mine - had a 1N4007 to hand, worked nicely!

[@bigclivedotcom]

A 1N4007 is maybe a bit too slow recovery for a switching power supply. The faster diodes are preferred.

[@gustavgnoettgen]

Nest is, I must admit, a great name for comfortable stuff. 1:0 for industries in general, nice one.

[@robinacjohnston]

Just fixed my Nest which had exactly the same issue. Only suitable diode I had to hand was far to big so used a couple of pieces of wire to relocate it to other side of circuit board. Luckily did not cause any noise issues. Many thanks

[@gatekeeper65]

Happy new year to you sir. I hope you have a wonderful year filled with good friends and good health.

[@kolabuzlu]

Hi. I’ve repaired mine using SR2100 diode and with your help. Thank you so much! Regards…

[@fazergazer]

Always amazing to see Big Clive handle the component and solder with one hand! Like chopsticks but even more tricky;)

[@drpipe]

Happy New year Clive.. nice little fix there. Seems the later versions of these ( after Google bought nest) have had issues. Bit fed up with being a kwick fit plumber these days. All manufacturers seem to have sold out. Have to be honest I wished I knew the level of electronics you do.. 💪💪 I’m sure many would love to do a course with you mate to understand more. All the best 🙏 Fab video as usual.

[@dotms5195]

Technically this isn't the thermostat (it's the Heat Link). Basically it's the relay unit that goes near the boiler. It wirelessly communicates over 868MHz with the actual thermostat on the wall, talks to the thermostat input on the boiler using either the relays or the OpenTherm interface. Also it provides power to the thermostat on the wall at the same time, using the wires running through the wall to (usually) the living room. Quite a lot of functions for such a small device actually.

[@MarcinLuszczyszyn]

You are my king. Thank you for helping me fixing my Nest

[@Tokaisho1]

Nice video, I have one of these and they are easy to set up/pair, you hold the big button on the front and it's in pairing mode.

[@AsymptoteInverse]

Security and support issues aside, I've never personally seen the appeal of the extra features that come with smart appliances like these. My regular thermostat is a new, bare-bones electronic Honeywell. I think it cost me $15 or $30 US, and it already does more than I need. Also, seeing this video, I almost wish I'd saved the old mercury tilt-switch thermostat from my dad's grungy workshop to send you. But in my excitement, I harvested the mercury switches and binned the rest of the corroded mess.

[@rpavlik1]

The number one advantage in these days of being at home all the time, is adjusting the thermostat from bed with the phone. Geo-fencing is much easier to set up than a programmable thermostat and can save a bundle of energy/money, if folks actually leave home.

[@dublinreliefdriver807]

Had this exact issue with one of my Nest HeatLink, fixed for the price of a Diode and bit of careful soldering. Thank you so much for making this video. Studied Electronics for 5 years over 20 years ago but ended up working in software, 5 years but couldn’t have fixed it without your help. Remember why I liked Electronics so much.

[@theoracleful]

Got one of these on my wall connected to my super old vulcan boiler, 5+ years now and the Nest still going strong.

[@Petertronic]

Excellent repair.

[@Huggs65]

Thanks for this. I had a weird issue with my dead base unit. I traced through the circuit and couldn't find any issues. I then found this video and evan though my diode appeared to be ok, I replaced it and all now seems ok. The old diode weirdly tests fine off the board.

[@alwayshardstyle1623]

Wow, thank you so much. Fixed my problem and works better dan ever 😊

[@JustinSable]

Nice vid. You've such a calm and reassuring voice btw

[@kevinquinn4764]

This happen to me 2days back and goggle nest replaced the unit even tho it was out off warrenty.was just about to try this fix with aid of this video.Worth asking them they were really helpful and even if not covered would provide replacement for 40 quid.Gr8 vid by the way.

[@Shaun.Stephens]

Nice fix Clive, well done.

[@cmbours]

Big thank you!! Same issue here, replaced the diode and were back online 😊

[@jacekmatusiak6184]

Impresive knowledge and skill Clive. Nice clip

[@richbouchard8603]

Amazing video. Can't believe such a small, cheap component can plunge us into a mid-winter heatingless deep-freeze. (For a couple of hours while I worked out how to bypass the heat link and just power the boiler via its on/off switch). I've owned four of these, in three different properties. Two have been solid ─ absolutely bulletproof running for four years or more without an issue. The other two (both in the same property) have both failed. One after 10 months. The other managed 15 months. Google, to their credit, have replaced both very quickly and painlessly, for free. There are two differences between the installation where the units failed, and the installations where the units have run without issue for years: 1) The failed units were installed with the 12V out feed connected back to the Nest Thermostat itself (the good units didn't use the 12V out as those Nest Thermostats are powered by USB and just talk to the heat link wirelessly). 2) The failed units were installed in an older, oil-fired boiler cupboard, with no pipe lagging, and it gets pretty warm in there. I'm guessing 45C or more. And, inevitably, that means it gets used as a drying cupboard for wet coats etc. So hot _and_ humid. Always good for electronic components! I've got a fifth unit on its way from Google as I type (to attempt a 'third-time-lucky' lucky installation at the property where two have failed). I've also got some pipe insulation/lagging on its way from Amazon to attempt to keep the boiler cupboard a bit cooler and will be keeping everything crossed that that does the trick this time. Anybody got an educated guess as to which of the factors above is most likely to be behind the repeated failures? (Assuming it's not just random bad luck!) Btw, the failed units had similar symptoms to the one in this video. No lights on the front. Manual override button not functioning. But I was still measuring 240V across the power in, the CH power out and the HW power out. Nothing on the 12V out (that's how I spotted the problem when the Nest Thermostat complained it had lost power) and nothing on either of the CH or HW demand lines. Also, also... for all the annoyance of the failures and the rigmarole of getting Google to send out new ones, the units are pretty straightforward to change out. You just wire in the new one in place of the old, sync it up to the Nest Thermostat and you're back in business. (For 10-to-15 months, apparently.)

[@bigclivedotcom]

The fact the two that had external 12V wiring failed is interesting.

[@richbouchard8603]

@@bigclivedotcom Thanks Clive ─ reading the other comments below I was coming to the same conclusion. I guess everything works that bit harder when the 12V is in use. Think I might leave that out on the new one when it arrives and just plug the Nest Thermostat in with its USB. Shame because the 12V output and re-purposing of the old thermostat wires is a neat re-use of existing wiring to allow installation of the Nest Thermostat in place of a traditional thermostat with minimal disruption.

[@jamesbronson8713]

Nice fix; We're fortunate to have you big guy...

[@BradTech.]

Those circuit board diagnostic skills 👌👌👍

[@KekTekDe]

Great vid as always! Just a lil suggestion; you could add the model number of these devices anywhere in the description so other people could find these videos by searching for "xx device fix" or so

[@holderbee7811]

Solder developes a layer of oxidation that acts as insulation; flux is for removing that layer of oxidation so the heat flows unencumbered

[@krisdevoecht]

Thanks for the good info, I have repaired mine and it works again!

[@neilmaycock3430]

Thanks for the video - repair worked a treat!

[@Alpejohn]

This is the kind of repair i wish i knew how to do.. I feel often that things that fail most likely is this "easy" to fix.. And it would be awsome to be able to do it my self. You wouldnt have a video that goes through what to look for to identify the path of power on a board by any means? My problem is that i dont know what all the parts do or what they are, but diodes i know, atleast the one you put on here cause i changed one in a parking heater i fried once and it worked great afterwards again :D But it was easy to find the problem as it had blown up.. hehe

[@ElectroDFW]

It justs seems so odd to me, seeing these repairs done without a Panavise (or other) PCB holder, and done by a right-hander! 😄 I guess I'm just so used to the way I do things. Lol Great job as always, Clive!

[@BrianthatiscalledBrian]

I do enjoy the "fix it" videos. Thans, Clive. 👍🙂

[@custardtart1312]

You know I don’t give a monkeys about what Clive is fixing, I just find these videos just so damn relaxing lay in bed at night. Sometimes I finish them and I can’t really recall what I’ve watched. No matter. Happy dreams 😂

[@jackpijjin4088]

I work in a place that deals in HVAC part distribution. The amount of 'smart' equipment we get back for warranty is obscene. Good source of relays for making magnetic pickups though.