waeco 40lt thermister not working again

possumyvonne · Senior Member

waeco 40lt thermister not working again

DeBe · Guru

This is where they are originaly.

DeBe · Guru

This is the recommended way of fitting, but be careful. 1. 100mm in & 25mm down, heat a 24-30mm metal tube & burn a hole in through to the evaporator. Clean it all the way in to the alum evap (do not drill). 2. Stick the thermistor to the ally evap with araldite. 3. Fill the hole with foam. 4. After dry cover with silicone. Borrowed the pics from another forum im on & they were posted in Waeco disassembly which I started, & pics were posted by bob& bev. THERMISTOR WAECO.1.jpg THERMISTOR WAECO.2.jpg THERMISTOR WAECO.3.jpg THERMISTOR WAECO.4.jpg THERMISTOR WAECO.5.jpg

03_troopy · Guru

Another very well illustrated post Darryl
Cheers

possumyvonne · Senior Member

hi daryl, nice talking to you tonight,
where the 100mm in and 25mm down, is the hole in the centre of the meet or does the hole start at the edge of 25mm and go towards 90mm
hope you understand what I mean
Regards Peter

DeBe · Guru

To me it looks like the center of where the measurements meet.

possumyvonne · Senior Member

yeah that's what I thought. Is the butter section on the edge of that 25mm, don't want to burn a hole in that section. I thought I would tackle the 35lt first, and not the new one, lol
Regards Peter

possumyvonne · Senior Member

Could you also explain to me how to check to see if the Thermistor is ok please and setting on the metre, I forgot
Regards Peter

DeBe · Guru

Unplug the thermistor lead from the board & check the resistance. Should read 10K ohms @ 25degC. Picture of a 10K NTC @ 20degC reads 11.49K. 10K NTC @ 20DEG C.JPG

possumyvonne · Senior Member

Thanks Daryl, if its not, buy a new one
Will put up my findings
Regards Peter

possumyvonne · Senior Member

Hi Daryl, just checked it and temp here inside the lounge room is 20c and the thermistor reading is 8.63
So what do you think
Regards Peter

possumyvonne · Senior Member

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Here is a pic of the new Thermistor Lead i bort from ALLVOLTS POWER SOLUTIONS IN BROOM WA, it measures 9.31 ohms
the end of it looks like it would slide into the white plastic piece on the above photo you put up
Can this lead be used in the way we were talking about
Regards Peter

-- Edited by possumyvonne on Monday 14th of April 2014 10:22:30 AM

-- Edited by possumyvonne on Monday 14th of April 2014 10:25:20 AM

DeBe · Guru

I would fit the new one you bought from Broom.

possumyvonne · Senior Member

Are You right for a chat if i ring
Regards Peter

DeBe · Guru

Yes having a rest from wood cutting.

possumyvonne · Senior Member

s1177.photobucket.com/user/peterfol/media/20140414_1151171_zpsbbd0e505.jpg.html">i1177.photobucket.com/albums/x343/peterfol/20140414_1151171_zpsbbd0e505.jpg">
Just cut the hole with a hot knife 4cm x 4cm in between the A &E on waeco
But i dont see the wire or the pipe
The hole was cut on the left hand side of the fridge with me standing at the compressor
Any ideas Daryl
Regards Peter

-- Edited by possumyvonne on Monday 14th of April 2014 12:07:56 PM

possumyvonne · Senior Member

-- Edited by possumyvonne on Monday 14th of April 2014 12:19:22 PM

possumyvonne · Senior Member

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possumyvonne · Senior Member

cleaned up

-- Edited by possumyvonne on Monday 14th of April 2014 12:53:55 PM

possumyvonne · Senior Member

there looks to be a bracket there so havent found the wire or the compressor pipe yet
Regards Peter

DeBe · Guru

I wouldn't go looking any further as they obviously don't put them all in the same place. just clean up the Evap & glue the thermistor to it. WAECO Thermistor placement.jpg

possumyvonne · Senior Member

Ive made the hole longer now 70 x 40mm and still no sign of any thing, glad this is my old fridge and not the new one
Regards Peter

possumyvonne · Senior Member

Yeah no worries Daryl, its a good experiment but will do, i was thinking that myself, at least now it will be an easy thing to get to
Am thinking of putting a hole into the grey face piece by the compressor and running the wire though there in a piece of hose, that way if it needs changing again, its only a matter of pulling out the old wire and pushing the new one throw, better than undoing the compressor
Regards Peter

possumyvonne · Senior Member

Cleaned up and glued the thermistor to the cabinet with araldite

-- Edited by possumyvonne on Monday 14th of April 2014 03:54:52 PM

possumyvonne · Senior Member

Just waiting now for 30 mins for the foam to go off, so i can cut it level
Regards Peter

-- Edited by possumyvonne on Monday 14th of April 2014 04:09:48 PM

possumyvonne · Senior Member

all cut and glued in, there is 3 pieces but was trying to find the wire. the fridge bag will cover the joins
I put a small hole on the out side of the compressor so now there is no need to take the compressor off at all
Quick easy fix, pull pieces out, did out foam, glue new thermistor in and plug in thermister to the board, stick piece bag on, ALL FINISHED
I would also like to thank DEBE ,Daryl, for his help on this
Regards Peter
bloody hell, hope it all works after all this

-- Edited by possumyvonne on Monday 14th of April 2014 05:52:31 PM

dorian · Guru

I've been reading this thread with interest and my first question is, why do these thermistors fail? It's not as if they're carrying a great deal of current. I have lots of negative experiences with corrosive yellow/brown glue in electronics, so is this what is causing the damage? I've seen a corroded thermistor in a spa pump, but that was due to water ingress.

My second question is, how can you be sure that the replacement thermistor follows the same temperature/resistance curve as the original one? AIUI, there are dozens of different curves, all of which could have the same resistance value at 25C, but they would have different resistances at 20C.

For example, see the following Epcos datasheets / application notes:

www.nikhef.nl/pub/experiments/bfys/lhcb/outerTracker/Electronics/CTRL-Box/NTC-100k/PDF_Standardized.pdf
www.epcos.com/blob/531152/download/2/pdf-standardizedrt.pdf
www.epcos.com/blob/531128/download/2/pdf-standardizedrt.pdf

The R20/R25 ratio for curve 1308 is 1.185. This means that, if the resistance at 25C is 10K, then the resistance at 20C will be 11.85K.

For curve 2006, the R20/R25 ratio is 1.3074, so the resistance at 20C would be 13.07K.

possumyvonne · Senior Member

Hi Dorian, i dont know why they pack up as this is my 3rd one in this fridge and my 40lt also has stuffed the thermistor as well, which really sucks as the fridge is only 5 years old and up to its 3rd one also
to answer the second part of the question is, the new thermistor is a genuin waeco lead made for the fridge and thats about all i know about them
Im very disapointed in these 2 waeco,s as they seem unleliable as far as the thermistor,s go
Thats the one reason i did the mod i did to make it easy to repair
Regards Peter
PS, Maybe DEBE, Daryl could asnswer those qs for you

DeBe · Guru

One of the problems with a Waeco fridge/freezer is poor insulation. If its used as a freezer for long periods & it humid, the foam insulation becomes waterlogged. I suspect this is what wrecks the Thermistor, as they are usualy open circuit. The 10K @ 25degC thermistor from Jaycar works in this application.

-- Edited by DeBe on Monday 14th of April 2014 09:29:31 PM

DeBe · Guru

This is how I mounted the thermistor to the Waeco Evaporator when I fitted it to the Evakool Esky. EVAKOOL THERMISTOR.JPG