Zanussi fridge freezer problem (the usual)

[izzzcold]

Hi all,

I'm new on this site, which I found by pure luck.
It looks like the right place to find solutions to fridge/freezers problems.

I have the usual problem: freezer ok but fridge not cooling.

Here are the facts:

Make: Zanussi
Model: ZK87/46EF (bottom freeze, upper fridge)
purchased: at Courts,UK, July 2000.

History:
faultless until about 6 months ago, when I accidentally left the freezer door open all night. Since then the fan (at the bottom right hand side back) seemed a little louder. Then last month the fridge temp alarm went ON (red light)and the fridge stopped cooling. We were advised to switch the unit OFF for 24 hours and restart it. It helped.

This weekend we went out and upon returning home yesterday evening I noticed the fridge was at room temp...

I've pulled it out, took off the compressor cover plate at the back, hovered clean everything.
The fan duct was pretty dirty (fluff). After cleaning that, the noise was completely gone (that's good).
I hear the compressor work, very quite though (but I'm not sure how loud are they supposed to be)...

Should I be looking for some blocked air vents from the lower part of the freezer to the upper part of the fridge?
Should I be looking at the thermostat that switches the compressor ON, and if so where is that thermostat?
The back (inside) of the fridge is a white platic panel with some sort of venting holes at the top.
In the middle, there is a vertical sensor-like metal tube, about 2" long, inserted in the panel. Is this a temperature sensor?

I'm basically quite handy and do not mind working on it, good case to learn something.
Any advice will be very welcome, as it seems daft to me to spend lots of money on a new unit if this can be sorted.

Many thanks in advance.

[tonto33]

need to check defrost heater and defrost timer

[izzzcold]

Tks Tonto33 for quick response.

I have found the Conveyor Heater, but would you happen to know where is the Defrost heater located?

And what should I test, continuity?

Same questions about the defrost Timer: Location and again, how to test?

thanks in advance.

[Bobby Drake]

Hi.

You won't find a defrost timer as the elements are switched on & off by the electronics. There are 2 heaters. One on the evaporator & one for the drain hole. Around 200 Ohms is a good reading for either for continuity.

One thing that can cause a problem is when the sensors go out of calibration as this causes the electronics to suspend the defrost cycle which chokes up the evaporator & ducts with frost & thereby causing temperature increase. This is not something that you will really be able to test for. If you find that the elements are ok then this is the most likely cause.

Please unplug from the supply before you attempt to work on it please.

[Bobby Drake]

One other thing. when you defrosted it, did you leave both doors open & are you sure it was fully defrosted as if not, it may just be a case of doing this.

Please advise.