Testing a Boiler Thermistor

[Neil Carroll]

I have a combi boiler Thermistor that may be faulty , it is screwed into a copper pipe to test temp of passing water , the water needs draining to take it out to replace , so it's a small inconvenience that I would like to avoid if necessary .,Im just wondering if I could test if this is the issue by unplugging the 2 pin socket that goes into it and bridging the gap with a small wire ( just for a minute ) to see if this corrects issue , or in fact just unplug it and test with wire unplugged ( again just for a minute ) . I'm not sure if the Thermister actually completes a connection or separates it when activated . As I say this will just be for a minute I appreciate this could be dangerous long term .

 

[davelx]

It's not like thermostat. A thermistor changes resistance with temperature, it doesn't have contacts.

If you can find the nominal resistance from documentation, you can check it with a suitable meter.

 

[Neil Carroll]

Oh ok thanks , I've actually ordered another one that is due on monday , I was just being impatient , I do have a meter , I'll find out what I can , thanks again

 

[Stuckinarut]

I do have a meter

Ok, unplug the connection and test the 2 prongs on resistance

 

[Neil Carroll]

Hi all , hope you are well , I've got an update on this that is confusing the hell out of me . The original Thermistor was working to a degree , I had a few old ones also from previous . The new one arrived , I installed it and attached the lead , nothing , doesn't do a thing to the water , stone cold , I took the lead out and put it back on the old thermistor that was detached , it clicked on obviously realising that the sensor was " cold " , I took the new one out and put the old one back in , I did the same with the new one , ( tried it whilst not attached ) and not a thing . I complained to the company and they said me another one , again it does nothing whilst attached or detached , it's not the leads , it's literally the 2 new thermistors , I ordered the new ones re the original part list , Id attach an image of both , however it's pointless, they are identical , can anyone offer any advice re this please , I've now put the old one back in and have 2 brand new ones !

 

[endecotp]

Have you measured the resistance?