Thermistor

[btkatzman]

I have a general question about Thermistors, Thank you in advance for your thoughts.

Are thermistors at all Interchangeable?

Say Fridge Thermistors (with similar open/closed ratings) Just like you can replace a similarly rated thermostat (as long as connection is same).

Also W/M and Dryer thermistor, i.e. are all the thermostat that fit into the heat element Interchangeable (if they are the same size, and similar open/close rating).

It seems to me that the open and close temps are not so often listed with thermistors as they are with regular thermostats. I hate the new technology lol

Thanks again,
Ben

[kwatt]

Re: Thermistor

In short, no.

Most have different ranges dependant on the application. Some info on fridge and freezer thermistors here:

http://www.ukwhitegoods.co.uk/help/fix- … stors.html

HTH

K.

[iadom]

Thermistor

Thermistors do not have an ‘open or closed rating’ they vary in resistance with temperature changes, this change is measured and acted upon by the pcb. They are never ‘open’ unless they have failed totally.

Not so much new technology either, in use for well over 30 years and more.

Sent from my iPad using Tapatalk HD

[btkatzman]

Re: Thermistor

Thanks Kwatt and iadom,

I guess I was hoping this would be more like a defrost timer, which I finally worked how to different ones even with the numbers in a different order.

Does the same apply for the NTC’s that go inside the heater element on dryers? Will they not work at all if I interchange them or just not at the same temperatures?

I am relatively new to the business, and always trying to learn new tricks. It always seemed to me that the older machines usually had the old style thermostats, and new ones often NTC.

Got this from Wiki “The thermistor was invented by Samuel Ruben in 1930.”

Thanks again 🙂

[kwatt]

Re: Thermistor

If you think about it, probably not.

There would be different casings etc depending on the position of the thermistor and so on. You’ll see them in metal and plastic cases, both materials have completely different thermal properties.

So, even if the resistance being read is the same, which you probably won’t know if it is or isn’t, there could well be different amounts of heat or cold applied to get to it. If that makes sense.

K.

[btkatzman]

Re: Thermistor

Fair enough, oh well I always love to find new tricks…

Thanks again 🙂

[leavemetogetonwithit]

Re: Thermistor

On the other hand, you may find that some manufacturers of washing machines do use the same thermistor on different models. It’s not much use from the point of view of swapping them around but it is quite useful to have an idea of the room temperature resistance of some common manufacturers’ ntcs so you know when they’re mis-behaving.
Could be worth having a sticky somewhere giving known values of these things as it’s not easy to find out for most.
Mike.

[Martin]

Re: Thermistor

leavemetogetonwithit wrote:Could be worth having a sticky somewhere giving known values of these things as it’s not easy to find out for most.

It did cross my mind to do just that Mike years ago but when I discovered the enormous variation from make to make, model to model I chose not to go there.

For example (at 25C):

Some Bosch, not all by any means, average = 11,000?
Zanussi, again not all but average = 5,000?
Hoover, vary wildly at best but a mean average of = 21,000?

Most obvious conclusion from that is that there ain’t no standard ohmic value. Each machine is different, each adopt a slightly different electronic control system. The best way to realise that is that all machines have different control PCB’s, all set with different parameters. 😐

[leavemetogetonwithit]

Re: Thermistor

I think most Merloni are about 25 – 30,000 at room temp. That’s just my personal experience, I’ve never read any technical specs on them. Nor have I taken temp readings when checking them. But a ball park figure is all you need really, because if they’re out and causing errors then they’re probably way out.
Mike.

[Martin]

Thermistor

Talking of Zanussi, I did have an ‘unfortunate incident’ with an AEG washer/dryer about 4 years back where the Heater was duff. It was the usual short length combined element/thermistor unit. I found, what I assumed was a suitable ‘pattern’ replacement on my van, and fitted it OK, job done. A day or three later the customer phoned to say that the machine had boiled the clothing within and had distorted the dispenser drawer due to the intense heat. Ooooops!

I returned and sorted the problem by exchanging the NTC with the one from the old duff element. A new Dispenser drawer front and a £40 M&S voucher to replace the damaged clothing. A combined loss to me in the region of 50 quid but a valuable lesson learned about the variance of NTC’s.

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