Used to work fine but performance deteriorated over time. Followed fault finding ideas at KEOGHS.AU and the fridge gets good and cold with the (in my older model the red) face plate removed, power to the+&- and a jumper across pins C & T. Seems to show a thermostat failure or, in this case a thermistor failing.
Stripped out cooling element and located the thermistor. First job is to test that device; it has an RJ12 “telephone” plug so I’ve order a screw in female plug
The unit has a separate control panel; this has a manual or auto selector switch and a potentiometer to control temperature when in manual mode. I think this, when in manual, adjusts resistance across the thermistor control channel circuit so that potentiometer is also a possible failure if it is in series.
A new thermistor from the manufacturer is around £130, the device itself is perhaps £2 but trying to get the specifications seems impossible. I think I can test the existing device and should it prove to be U/S I will get the scalpel out, carefully strip the cover and see if I am lucky and the specification is showing.
I believe I have found the fault after many false trials. It looks like the RJ45 cable ( popular interconnect) has failed. A visit to Gamma and a new cable for 6.99 and now ready to test and prove that out.
Some resistance values for the thermistor as the evaporator plate gets colder. Seems we have Negative Temperature Coefficient (NTC) thermistor. Ambient temperature at was around 25C prior to start of cooling. These numbers might help if you are trying to replace the thermistor but do not have a specification. 2.28 Kiloohms @ 25C, 3.7 @ 12, 4 @ 9, 5 @ 0.5 6 @ -2, 7 @ -16.
Since the cooling element of the fridge is running at full tilt the overall internal fridge temperature would not get down so low as -16 so I am guess the thermistor cut off value is around 4 KiloOhms. Enough, time to put it all back together.
RJ 9 or RJ 11? Grrrrr, seems the thermistor lead has a different connector ( I guess to stop you plugging the two leads incorrectly! I’ll try using the old plug and a bit of cable and see if that works.
