Brandt fridge freezer – fixed at last!

I thought I should contribute to this very helpful forum with the story of the repair to my Brandt Apollo CFA311WU fridge-freezer. A couple of years ago, it started to warm up and defrost the contents. Called out an engineer, he took the internal back wall and foam insulation out and found the evaporator solid with ice. Melted the ice with a hairdryer, including the ice in the drain pipe, and fitted a length of copper wire through the pipe, with the upper end wrapped around the defrost heater element to help keep it clear – a trick recommended by the engineer. All OK for a few months, then froze up again. I found it solid with ice again, defrosted it again and all OK, but this needed to be done every few weeks. I then checked the defrost heater element – it tested open-circuit so I fitted a new one (73 quid). When I looked a little closer at the old element, I found that the element itself was OK but the small black square unit in series with it was open-circuit, at any temperature. This is not available separately, it is part of the new element assembly. All OK again for a while. Six months later, iced up again – tested the defrost element, same as last time, the black box was open-circuit at any temperature. I wasn’t going to spend another 73 quid so looked around for a replacement for the failed part. It is a temperature switch which cuts the power to the defrost element if it gets too hot. It is marked “72 degrees” which must be Fahrenheit, equal to 22 degrees Centigrade. I found a 20 degree C temperature switch (opens above 20 C) on the net for 3 quid and soldered it in place of the failed part, insulated the joints with heatshrink and rubber self-amalgamating tape (as it’s 240V). This should be more reliable than the original solid-state item as it’s a conventional bimetal-operated switch with ample current-handling capacity.
Did this fix it? Not exactly – the element heated up when the defrost cycle started, and the temperature switch cut in and out as expected, but the defrost cycle went on for over 2 hours before it ended and the compressor re-started. By this time, the heat put in to the cabinet by the element had raised the temperature to around 0 degrees. Not good. The other thing I noticed was that when the defrost cycle started, the green lamp on the control panel blinked on and off about once a second, and the power to the defrost element was also pulsing on and off at the same rate. I had no idea if this was normal or not – there is no mention of a flashing green light in the operating manual and I could not find any helpful information.
I suspected that the circuit board might be faulty, as I had checked everything else I could think of (including both of the temperature sensors). Decision time – spend 80 quid on a new PCB or take it to the tip and buy a new one? Problem is, we need a unit with a large freezer and small fridge, with a maximum height of 1750mm and this is the only one we know of, so prefer to repair it if possible. Checking the forum, it seems that the PCB is known to be troublesome so I ordered and fitted one. Problem solved! It now defrosts regularly every 36 to 48 hours, the green light is always steadily on even while defrosting and no ice build-up. The defrost cycle timing seems a little odd – the element is powered for 15 minutes then switches off, and the compressor starts up about an hour later. Doesn’t seem to be a problem, the cabinet temperature rises to about -12 degrees from its normal -22 to -25 degrees although the temperature in the food drawers never rises above -20 degrees. I used an electronic thermometer with a sensor on the end of a long wire which lets me check the internal temperature without opening the door – about 12 quid from Maplin.
Small tip – when you refit the plastic back panel, use longer pins to secure the plastic rivets and leave the ends sticking out so you can pull them out next time with pliers. I used 1 inch lengths of plastic wire insulation. I read on the forum that someone had not refitted this panel as they didn’t think it did anything – look at the back, it’s got ducts to guide the chilled air into the drawers.
I hope this long saga is helpful.