NTC Thermistors

That would sound like an inrush current limiting thermistor. Its failure may be caused by repeated power cycling or something going wrong downstream (e.g. short circuit).

The rating is not very indicative - 3.15A could just be the expected maximum holding current, in which case something that's rated 3.0-3.2A might be okay.

But we know nothing about its steady-state on resistance, energy rating or size which is quite important. Perhaps if you can see if there are any markings left, or even a good macro photo might be helpful.

Rarely is a failed component not without a particular cause, so it's good to know what is the cause before just replacing things ad-hoc. Choosing one without the right energy rating or steady state resistance could cause the replacement to burn out too and cause a safety issue.

- Gough

Hi Gough, thanks for your input. Have a look at the photo 

Ah. That's a switchmode power supply using the NTC as an inrush current limiter.

The 3.15A rating is actually for the fuse underneath, not the NTC.

As a result, we still have no idea what the exact type should be. You could take a measurement of the distance across the legs to give a vague clue about the disc size of the NTC. But as to its actual value - perhaps you need to find a similar unit to check, or else make some guesses. Unfortunately, if you guess too low - it may not be effective and you may blow the 3.15A fuse randomly on plugging in/powering up. If you guess too high for resistance, then it could end up staying warm/hot and impeding the efficiency of the supply, eventually cooking itself to death.

If you know more details, you could perhaps calculate the right value using something like this: https://www.ametherm.com/blog/inrush-current/calculate-inrush-current-three-steps

- Gough

Ah. That's a switchmode power supply using the NTC as an inrush current limiter.

The 3.15A rating is actually for the fuse underneath, not the NTC.

As a result, we still have no idea what the exact type should be. You could take a measurement of the distance across the legs to give a vague clue about the disc size of the NTC. But as to its actual value - perhaps you need to find a similar unit to check, or else make some guesses. Unfortunately, if you guess too low - it may not be effective and you may blow the 3.15A fuse randomly on plugging in/powering up. If you guess too high for resistance, then it could end up staying warm/hot and impeding the efficiency of the supply, eventually cooking itself to death.

If you know more details, you could perhaps calculate the right value using something like this: https://www.ametherm.com/blog/inrush-current/calculate-inrush-current-three-steps

- Gough