Author Topic: Replacing NTC thermistor in old coffee maker  (Read 601 times)

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Offline Philly_Dee

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Replacing NTC thermistor in old coffee maker
« on: August 19, 2018, 03:16:31 pm »
Hello all,

I am trying to get my old coffeemaker to work after it stopped heating. This is a common issue I think after a few years.  We've already bought a new one, so this is strictly for "fun" and to learn a few things. It's a KRUPS KM720 that I always liked.  I've already bought two thermal fuses to replace the old ones : Microtemp G4's rated at Tf = 184 C. I'm pretty sure they were identical, placed on either side of the heating element. 

My problem now is replacing the small NTC thermistor (glass-encased bead type), which is placed against the element (with some white stuff in between, for thermal conductance ?) and looked very much like these :

Unfortunately I've lost the old one, but before that I was able to measure its resistance at between 10k and 20k Ohms (at room temperature).  However at the electronics store, one guy measured it at 100 kOhms on his multimeter. But we were wrongly assuming at that time that it was a zener diode (which can look quite similar except for the black band at one end, not present in my case), so his measurement may have been at the wrong setting.

My question is: does anyone know what specs would make sense to replace the NEC thermistor in this coffee maker?  From what I understand, the two parameters are resistance at room temp (25 C) and the B / beta which characterizes the rate of change versus temperature change.  From what I see on e.g. Amazon, the most common specs are 10 kOhms and beta = 3950.  But of course the original design could have called for different specs.

Thanks for any advice.

Offline joseph nicholas

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Re: Replacing NTC thermistor in old coffee maker
« Reply #1 on: August 19, 2018, 04:07:04 pm »
Hi, first welcome to the form.

Since the old one is not available, may be you could get a schematic somewhere and find the old part number.

Just off the top of my head I would think you would need to know the temperature vs the resistance of the part in order to find some like part.

I'm sure others here have the same coffee maker so they could be of help.

Good luck.

Offline ogden

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Re: Replacing NTC thermistor in old coffee maker
« Reply #2 on: August 19, 2018, 04:17:30 pm »
I just googled for few minutes and appears that 1) service manual is available online, 2) you can buy spare parts from krupsusa. Part you are looking for is "44718  NTC­temperature sensor complete.". Disclaimer: it's not my typo.

Offline Philly_Dee

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Re: Replacing NTC thermistor in old coffee maker
« Reply #3 on: August 20, 2018, 02:16:05 am »
Thanks for the replies.  Unfortunately the service manual is for another coffee machine (they don't have it for model KM720), but perhaps it's the same sensor.  I'm not sure how to order that part from Krups but I will contact Krups Canada to start (the USA corporate divisions don't always deliver to Canada).

I'll let the forum know how it goes...

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