Domestic fridge HELP

Hi all, my name is martin and i have signed up to this forum with the hope of gaining some technical information on the correct operation of my domestic fridge. I am a complete novice in the refrigeration trade, but i am a technician (aircraft) and one of my pleasures in life is gaining the self satisfaction in tampering and (sometimes) repairing faulty items. I have an upright Hotpoint RF64 combination fridge freezer on which about a year ago an annoying red LED decided to come (and stay) on. I found out that this LED indicates that the freezer compartment is not reaching the required temperature -18 C, so i started my investigation. I found that this combo has its only thermostat located in the fridge compartment, and that this thermostat governs the operation or length of time the freezer compartment is supplied with refrigerant (how strange). The freezer has 4 compartments,with the top compartment having a fast freeze facility, which has the ability to reach -22 degrees C, which i thought was ok (but only after a very long time on the very coldest setting on the thermostat). I then discovered that the temperature sensor is located in the bottom compartment, and that this compartment stuggles to get below -12 on any thermostat setting. The thermostat cycles on and off regularly at all settings, apart from the very coldest setting of which it seems to keep the compressor running almost continuosly. I monitored the temperature on the evaporator in the fridge (on which the thermostat sensor is located) and this also seems to stuggle to get below -12 C (have no idea what temperature it should reach on coldest setting), and wondered if there is connection with this temp and lower compartment temp. I feel that the thermostat is operating correctly (although i have no idea of the operating temperatures of the thermostat either) but never sees the temperature that it is meant to and never trips off on the coldest setting. I was wondering if there is a lack of refrigerant in the system, and if so would this be a prime example of these symptoms. The unit is only 5 years old and i was expecting it to last for at least double this. I would be extremely helpful for any advice offered before i have to reluctanly call in a professional (I have to fix it as it has become a challenge now).

many thanks, Martin

Hi Martin,

Domestic fridge freezers are common for having temp problems like this the way they usually work is this.

The fridge has the stat as this is the temp you have to control more. The system then works by feeding the evaps in turn starting with the coldest through to the warmest where the stat should be. the idea is that the colder evaps get the gas first and the cooling capacity aand work there way down to the fridge. In theory by the time the fridge being last in line get to temp the freezers should be at temp.

Now common problem, Fridge freezer in garage, cold ambient so stat never comes in therefore freezer will never cool as fridge stat doesn't call for it hence defrosted freezer.

Basic checks first, unlikely gas lost, domestics usually reliable unless someone taken i kniff to the freezer to defrost so assume not that. Check the condenser, Might be a plate on the back or a grille (Like a car Rad) down the bottom, check its clean and not full of dust and if its got a fan on it check it comes on with compressor.

Check freezer not too iced up and therefore cooling capacity being lost keeping ice in place.

I hope my description of how it works makes sense, it does in my mind but that doesn't always mean i am explaining it well, any questions please post and i am sure someone will come up with a more english explanation

Regards

Fatboy

Hi Martin,

Yes, only the top most compartment is supplied with refrigerant and the cold air is circulated within the system via a fan motor.

If the top compartment is iced up (due to a defrost timer/heater problem), the ice will jam the fan or bloct the air passage ways thus not sending the cold air downwards.

Unless yours is an electronics pcb card controlled system, the defrost timer can be found at the bottom back of the fridge. If this timer works, it will enter a stage where it shuts down the compressor and turns on the heater, thus mealting any ice. Defrost cycle can be as long as 1 hr.

Normally there's a small window where you can see the movement of the small plastic gears if the timer is working properly. If timer is ok, you need to check the heater which means you need to strip the freezer compartment.

Feel free to drop me a mail shld u require any further assistance.

good advice thanks.