[nivard]

This is the common refrigerator with a freezer compartment on top.
The freezer stopped freezing while the fridge worked properly.
I tested the various switches without finding a fault.
Finally I disconnected the heater and that seems to have solved the problem.
Now what I need to find out is what part do I need to replace?
The defrost timer?
Thanks

[nivard]

I found that the 'Defrost Timer" is faulty and will replace that. If you have a similar problem then this is what I did. I unplugged the fridge. I removed the back of the freezer. Five 1/4" screws I think. I removed the two screws holding the fan in place and manipulated the fan through the hole so that the back panel would lie down. This gives good access to the heater which is a thick wire (?) draped around the fins. It is connected on either side , to the electrical supply, by push fittings. I disconnected both sides , though one would do. I replaced the back panel, using one screw to hold it in place. I replaced the fan. I plugged the fridge in and waited for a number of hours until I saw that a bottle of water had frozen.
Deduced that the heater was the problem and found out that the ' defrost timer' controls the heater. Tested that with the help of DIY Home Repair Guide: Learn How to Make Repairs Around Your Home at ACME HOW TO.com refrigerator repair guide. Found that it was bad. Perhaps I took the long way round? I'm happy anyway.