How to test a Thermistor - Combi boiler faults - Multi Meter Fault finding

[@ericmcrae7758]

Hi Allen I am an electrical engineer (retired I feel better now). It is important to isolate the thermistor as you could be reading the circuit PCB if you try testing the resistance with it connected, this may sound obvious but you would be surprised how often this mistake is made.

[@AllenHart999]

I actually meant to say to take plug off and test from it. Thanks for the correction 👍

[@nightrider8918]

Hi Matey, So I have been reading that resistance goes up with temperature increase but in this video the chart shows the opposite. Higher the temperature the lower the ohms. Please advise.

[@shaunhw]

@@nightrider8918 There are two basic types of thermistor. NTC and PTC ( Negative and Positive Temperature Coefficient) and for NTC the resistance goes lower as the temperature increases. For PTC the resistance goes higher when the temperature increases. Note that different types of thermistor can have widely differing resistances at any particular temperature, so you have to get the correct specification of part when replacing these items.

[@yensabi]

Nice one Allen , I usually cut off the plug leads on the ntc's of replacement boilers I fit and keep them in my spares box as most are the same on all boiler makes and if you have a few different ones you'll find one that fits for testing purposes......👍

[@AllenHart999]

Thanks for watching.

[@smellslikethinice1107]

Thanks Allen, thank you for all your support !!!

[@smellslikethinice1107]

Great job as usual Allen. Thank you for all your support !!!

[@AllenHart999]

Thank You

[@cosmocandle]

Great video Allen, thanks for taking the time to do these.

[@AllenHart999]

Thank you for watching please give the video a like. 👍

[@rayeugene8139]

Sorry to be so offtopic but does anybody know a trick to get back into an instagram account?? I somehow forgot my password. I would love any tricks you can offer me

[@brucedenver2731]

@Ray Eugene instablaster :)

[@rayeugene8139]

@Bruce Denver thanks for your reply. I found the site on google and I'm trying it out now. I see it takes quite some time so I will get back to you later when my account password hopefully is recovered.

[@rayeugene8139]

@Bruce Denver it worked and I actually got access to my account again. I'm so happy:D Thanks so much, you really help me out :D

[@virgilpetrut618]

Great video. Very useful. Congratulation Allen.

[@liamh2467]

Numba on and farr 😂 quality 👌 great vid as per Alan.

[@scottwilliams1094]

Very interesting video Alan. keep up the good work 👍

[@arianxhebraj6107]

Fantastic video...THANK YOU ALLEN!!!!

[@AllenHart999]

My pleasure!

[@TheHicky46]

Great video. Just a question should the Thermistor have a washer on it. Im changing mine today. New one come through post but no washer?

[@jmqmin]

Best video you have done Allen 👍

[@AllenHart999]

jmqmin Thanks 🙏

[@stewartharrod8562]

Superb work really enjoy these videos

[@AllenHart999]

Glad you like them!

[@madshepsreef282]

Hi Alan I’m testing a thermistor on ohms and all I’m getting is the lead resistance. Is this correct if it’s broke

[@levimust4479]

Thank you thermister Hart.

[@AllenHart999]

Thank You

[@daleprosser350]

Hi Allen, I understand the relation between ohms and temperature now, but why would you need that information? Is it to test whether the water leaving the tap is the correct temperature that you’ve set on the boiler, for instance, if it’s testing at 50 degrees on the multimeter, would you have to check the actual water temperature at an outlet with a thermometer? And if they aren’t matching, would that mean a fault in the thermistor? Thank you!

[@AllenHart999]

They normally just stop working tbh. Thanks.

[@TheHicky46]

Also does new one need ptfe tape on it?

[@ratchriat1716]

thanks Allen for sharing this information with us enjoyed the video.

[@AllenHart999]

Big thank you to Roy Fugler from Baxi Boilers as he did my refresh training. Thanks.

[@cruztom4325]

Hi Allen you best teacher, could you tell me which baxi Breakdwn course is better, I’m trying to find but there are so many choices so which is better and if you have link with that could you write please?

[@taz1058]

Allen how can I get one of these manuals? I've been on the Baxi course too but they never gave us any manuals.

[@ek6868]

Tanx for the upload allen best video ntc on youtube👍

[@AllenHart999]

Big thank you to Roy Fugler from Baxi Boilers as he did my refresh training. Thanks.

[@eddiestafford3313]

Great video...very well explained...thank you!!

[@AllenHart999]

Thank You

[@markstewart1807]

Do these drift much over time? Or go from working to complete failure,open circuit or short circuit?

[@abualam4418]

Great video Allen👍👍

[@nightrider8918]

Hi Matey, So I have been reading that resistance goes up with temperature increase but in this video the chart shows the opposite. Higher the temperature the lower the ohms. Please advise.

[@rosstaylor4924]

Another great video Alan👍

[@AllenHart999]

Thank you.👍

[@stevem856]

If your hot water is running cold then hot , could it be a thermistor fault...

[@gwnaylor]

Such a clear and helpful video! Thanks ;-)

[@TheMarwind]

Allen would you say that thermistor resistance reading document is service manual?

[@TheMarwind]

Oh sorry I miss it u said engineers book Allen thank u.

[@AllenHart999]

👍👍👍👍👍

[@suheilhanna873]

Hi, do you mean boiler temperature or room temperature please?thanks Training

[@nayzhoss8744]

Great teacher as usual , do you need to complete baxi course to get the engineer manual or you can buy from .

[@AllenHart999]

Yes.

[@nayzhoss8744]

Thanks for your reply mate stay safe

[@rickysheldon4355]

Top work Allen NTC aka Negative Temperature Coefficient sensor use them in washing machines. Saved 100 quid call out and put a new NTC for a couple of quid in a friends washing machine.

[@raquelsapalaran2907]

great video thank you for sharing your knowledge...

[@shilks8773]

You could have explained that OL on your Multimneter means "Open Line" - (No Circuit).

[@AllenHart999]

Thank you.

[@plautisantgrindu916]

Hello, my boiler Beretta, would not keep water temperature the same if I shower or even wash hands. Boiler seems to turn off after some time when it "reaches the right temp." so after this water temperature drops few degrees, sometimes drastically. Could this fault be the problem of mine? Thank you

[@AllenHart999]

Thanks very much for your comment, please consider subscribing to support the channel 🙂

[@bobdigi500]

How much should a thermistor replacement cost?

[@saiello2061]

Hi, is it necessary to remove the thermistor to test it? Will it affect the resistance readings if you leave it in place?

[@AllenHart999]

No, You can test it in place. Thanks.

[@saiello2061]

@@AllenHart999 That's great, saves me a bit of bother. Thanks! 😁

[@arts82]

very helpful, appreciate it man!

[@AllenHart999]

Glad it helped!

[@jasonmurphy435]

nice one.im not a plumber but very interesting and could come in useful👍

[@davebayliss3142]

Alan you are a god to me 👏

[@AllenHart999]

Thank You

[@ΑΛΕΞΑΝΔΡΟΣΛΑΠΠΑΣ-ν7ζ]

Thank you for your videos can you upload the manual?

[@AllenHart999]

I will try and add it to a video. Thanks.

[@TheKingTywinLannister]

Hey. Thanks for info!

[@chikemadekwe4342]

What's going on ere then guv ? I distinctly remember you stating NO ADS in your videos Allen, I've just had three during this one. Thank you for posting though.

[@AllenHart999]

No ads on the videos that have been sent in. Some of the videos I do have ads. I spend 2 or 3 days a week doing videos and still have to live, thanks

[@chikemadekwe4342]

Allen Hart That’s the trouble with txt you can’t tell the emotional intent of the message sometimes. It was only said in jest, my apologies if it offended you.

[@davidtaylor3538]

brilliant thanks for showing 👍

[@maxnavsa4470]

Brilliant video Allen. Finally had my baxi 836 installed last week on your recommendation. Im sure i wont be needing to do this test in a long time.😉. I cant believe how quite it is compared to my ideal isar. Thanks Allen for all your video reviews for helping me decide which boiler to go for. Buy the way how's the loft conversion going?

[@AllenHart999]

Loft is going well, It’s all been plastered, Just needs paint. Thanks.

[@garylawton7254]

@@AllenHart999 would faulty ntcs cause the boiler fuse spur to blow please Allen? Or is the pcb itself likely to be at fault thanks its a F64 fault code on a vaillant ecotech plus? Your clips are great BTW cheers

[@yensabi]

Gary Lawton .....Hi , F 61 to F67 fault codes usually indicate a fault with the PCB board and you will more than likely need to change the board...👍

[@garylawton7254]

@@yensabi can you test the board somehow?

[@yensabi]

Gary Lawton ....Not really mate other than a visual inspection to see if there is any obvious damage , best bet is to take it out and get a reconditioned one for about £70 and that way if it's not the board you haven't wasted £ 150 , there are a few company's that do the re con boards , just send in your old one as part ex........👍

[@redachauffagiste5041]

you are the big boss

[@AllenHart999]

Thank you.

[@7odaeto295]

please if you can share the engineering book

[@AllenHart999]

Thank You

[@SK-fv6sf]

Old baxi is gold

[@AllenHart999]

Thank you for taking the time to watch my video.

[@charliesebbage9401]

I changed a thermistor once in the first boiler you showed & snapped the heating pressure sensor off from the block 🤭 it was plastic & very brittle & I was dumb

[@AllenHart999]

Merry Christmas

[@anthonybennett3616]

Great video thanks👍 So obviously if the k Holmes are low when the boilers cold, and vice versa, the thermistor in knackered?

[@TheIcebon]

Hi Allen, have you thought about setting up a training academy in your boiler room?

[@AllenHart999]

😂😂😂😂

[@cjhatescomputers]

That’s what he is doing

[@dangas6422]

What book are you use???

[@AllenHart999]

👍👍👍

[@dangas6422]

@@AllenHart999 can you show step by step.how draim boiler

[@macker6464]

Great video. Very informative fella. Cheers

[@crazygeorgelincoln]

Always a pleasure. My multimeter cost under a fiver.

[@garylawton7254]

Are the cheaper multi meters OK for the odd repair I only need one for a single job of checking the ntcs on my vaillant ecotech plus as there's aa F64 code showing off and on

[@AllenHart999]

Thank you for taking the time to watch my video.

[@peterstencell804]

Should subtract LEED resistance

[@Robert-ts2ef]

It’s actually terminal 1 and 4 on the diagram. Just a comment

[@parko1965]

Any sparks watching this?

[@AUranus_urmom]

Thank you

[@hectorheath9742]

Hi Allen my new boiler instructions says 5 inches for the flu hole in the wall. The existing hole from the old boiler is 4.5 in, but a local supplier says the new flu is 4 in (100 mm) dia. Do I still need to re-do the hole so that it's 5 inches for my new Ideal 30+ logic?

[@TheIcebon]

Get a gas engineer to do the work 👍

[@AllenHart999]

+Hector Heath Make sure you use a gas engineer/plumber it’s not worth it, they will be able to sort the warranty and building regulations, Thanks.

[@simb3867]

what 'book'??? what if it was a ptc??? ooer

[@AllenHart999]

Not sure what you mean? Thanks.

[@markcarruthers7768]

Think he means the thermistor type you said yours was a NTC and sim b mentioned a PTC ,Your type of thermistor is a negative temperature coefficient one (NTC) but you can also get positive temperature coefficient ones (PTC). Basically they are the same devices but work in a reverse manner. Namely the resistance of the positive one goes up with an increase in temperature and the resistance of the negative one goes down with an increase in temperature.

[@Falco45able]

Would that be terminal 1 and terminal 4 ? 😉

[@AllenHart999]

I cannot remember now 😂😂😂😂Thanks.

[@jaycrossland30]

Someone’s just had a training class from Roy @baxiboilers 😂

[@jaycrossland30]

That’s not one of his tester choc blocks is it ?

[@AllenHart999]

Yes I went on training yesterday to recap, also did the training about 2 years ago. That is Roy’s tester 😂😂😂

[@MrHukd]

Baxi make it so easy for engineers to diagnose. Including giving you extra references if you do the training course. Why dont Worcester offer this instead of having to mess around on the phone to them everytime😡

[@AllenHart999]

Baxi have got rid of some of the trainers now.

[@MrHukd]

@@AllenHart999 oh no really! Well that's a shame. But I'm glad you post what you do Alan. I'm just starting out on faultfinding and your vids are truly so helpful🙏

[@AllenHart999]

@@MrHukd Thank You.

[@rezuk1208]

💝💝💝

[@peterstencell804]

Test in ice water for accuracy

[@ryanmonk4451]

You cam explain your videos in much less time