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

my name's on hat and today I'm going to show you how to test a famine sir if you need to test a thermistor in a combi boiler if you've got problems with with the ball not work and I'm not working correctly and going to show you how to test the thermistor I've got a few different boilers here we've got buck c800 I've got an old buck see duratec we've also got these men so can I put some different different for misters in the boilers we can test them cold and also a bit on this boiler here because this one's working but to test it hot as well just to show you the different different readings in the boiler so let's have a look now before we remove the case we'd make sure that we've tested it doubles electrical checks make sure the boilers turned off so this foil is not connected so I know this I know it's not connected so I'm just going to do these two screws here when we look in the boiler here this is the for mister here boxy coal they said domestic hot water NTC sensor and that is that's what for mister is and what we need to do we need to test this so we need to test there's two prongs in there and we need to test this on this video what we wouldn't do is I'm just going to do this out this is the on this particular one it's a 13 mil connection so what would do is we just don't clip that off that's got a little clip on there so normally we'd just clip that down and then which gets 13 mil cause bummer so we get the 13 mil spanner and then we'd obviously we just done do this here now just to bear in mind with this particular boiler this is a wet pocket so if you disconnect that out of there then you're gonna get men's what I pressure it's growing out of there so you need to make sure that you turn your water off and opened you hot tap and Mitch I know what I want flowing through before you did it just another way just before we do undo that there you can also you could do it on the board if you want it to so you could remove this cover there and then if you have a look in the manufacturer instructions you can see where these green wires go to and then you could test it on pard and on this particular one I think it's X 400 but I'll just we'll just other just check it out so I've been on the buck see trilling cars and I've got the engineer service manual for this boiler and in the engineer's service manual you can see there the electrical information and you've got your domestic hot water NTC sensor so that's your temperature sensor your for mister and if you follow our wires down they go to the plug X 400 there and if we have a lock its terminals one and terminals free so we could if we wanted to we could chest it in there and we could put as multimeter into there and test it but I'm gonna remove I'm gonna check this finish turnout on this so we'll have a look at it first of all what I'll do is I'll show you the I'll show you the multimeter and I'll show you how we test it a little bit hard to see but to show you this now I said it was terminal I said it was number number one and I said it with number three he's not telling number one and it's number far so if you're gonna check it at the bar you would check it at number one and number far I'll just get the multimeter now and I'll show you the multimeter so this is the combi boiler combi boiler for mr. or bylaw thermistor or combi boiler combi boiler a sensor or bucks a temperature sensor our bucks if a mister and this is what we're gonna test there if you can have a lock on there it's a little bit hard to get in and get onto their Myers so what I'm gonna do is I'm just gonna cut the lead off the boiler just to make it easier for us for this test now and but first of all I'm gonna show you I'm gonna show you the multimeter so if we look on the multimeter I've got a fluke one one far multimeter and what we want to do we change it to arms on there so ohms and then what we'll do is if we have a lot come you see on there that's sure sure mm ohms and one we'll look at what Emma M arms means so that's a mega and a mega arm is 1 million arms I've got a lot of tester block here so I can show you the different the different readings of my so that one's M ohms and then if we go to the next one this one now if you see there is care arms and if we have a look in the book what care rooms is there so it's care arms so that's one thousand arms and then if we have a look again if we gone to this one and we have a look on there that one that's just arms so you just need to be careful when you're doing your readings that yeah you see in the right reading so let's have a look at the semester now so I've got is for mister now and I've just cut the lead off out of the boiler and I've just bared the wires back obviously you wouldn't normally do that but if we connected this if I put it right around and connect that onto there and then what we can do now so this for mister now is going to give us a reading or it should do if it's if it's working up here that should give us a reading at whatever the room temperature is now so what we'll do we'll test that now with multimeter so again put this butter arms how could you say I'll just zoom in with that I'm gonna calm this for mr. he cook if you can get more to me to them you could test it on them chill pins there as well oh you could take the wire off as I already said and you could test it on the pins in there or you could test it out the circuit board depending on the make up boiler so when we test this now we test this with multimeter so for test one side and then just come aside so what we've got there we've got ten point eight three care homes remember what care means it's all care homes right if ever look in the book or you could if you don't up the book so so that would be ten thousand ohms so it's roughly about twenty five degrees so let's just have a look at that again so it's roughly about 25 degrees maybe a bit less so it may be about probably about 23 degrees actually so this is the engineer's book if you don't have this book with these different readings in these different resistance re readings then you could form the manufacturers and the manufacturers will will give you I'll tell you what the what the different readings should be when we look at this chair we can see as the temperature goes up the resistance goes down if you say so if it refers to degrees resistance would be about eight thousand ohms if it was hundred degrees it would be about seven hundred ohms and one thing to point out with this if it's not working well or if it's not working then then you Mir geht you may get Lorrell and that if you do get or al then you know the thermistors not working i've put the hot water for mr. or temperature sensor back in the boiler and on this boiler so I also got for mr. on the central heating side here so you could test that one as well so I've had this pile of running this reason this is a reason and combi boiler and this this is hot now so what we'll do I'll just show you the difference and we'll test this this for mr. here I've turned the power off to the boiler and I've done the electrical checks so we'll get this multimeter now and I'll show you the readings on this so again we turn the multimeter to arms that getting free six K ohms I'll just zoom in I'll just show you so I've just zoomed in now I'll just do that again so again 3 point 6 K ohms so that's three thousand six hundred ohms r3 point 6 K ohms so if you're ever looking as Bock well I've locked in the box of Bach now that was an indication if it was in a box a obviously this isn't a Vizsla so I know these men you would check with the manufacturers so if we have a look in the box a Bach three point six or three point five eight five is around 50 degrees temperature so we can see that the higher the higher the temperature the lower the resistance on there so that's that's just a shop video on testing for misters what I would advise if you're not sure go on all right even if you are sure really go on a training course we'll find the manufacturer and Boxey do box into a very good training coughs and if you found this video useful please please please please give it a like and click on subscribe button if you can if you click up here subscribe button should be up here somewhere and up here and down here and also add some of her videos as well thanks very much for watching

Channel: Allen Hart

Views: 68,999

Keywords: boiler repair, thermistor testing, thermistor temperature sensor, thermistor, combi boiler thermistor, troubleshoot thermistor, combi boiler sensor, combi boiler fault finding, combi boiler fault, temperature sensor problems, fault finding, combi boiler, boiler fault finding, thermistor sensor, combi boiler no hot water, fault finding with a multimeter, gas boiler fault finding, how to fix boilers, boiler repair training, multi meter

Id: 1mDoh9V9IEA

Length: 13min 23sec (803 seconds)

Published: Thu Oct 03 2019