Fridge repair in Githurai.

A fridge does not make cold. It moves heat. Inside the sealed pipework there is a refrigerant gas. The compressor squeezes the gas, which makes it hot, and the hot gas flows through the coil at the back or underneath, called the condenser, where it gives its heat to the room. The gas turns to a liquid, passes through a very thin tube that drops its pressure, and arrives in the cold coil inside the fridge, the evaporator, where it turns back to a gas and soaks up heat from the food. Then it returns to the compressor and the cycle repeats.

That is why the back of a fridge feels warm and why a fridge squeezed into a cabinet struggles. If the heat cannot leave, the cycle slows and the compressor runs for longer. It is also why gas does not get used up: it travels round in a closed loop. When a fridge is low on gas there is a leak, and the leak has to be found and sealed first.

In a no-frost fridge a fan blows air over the evaporator and into the compartments, and a small heater melts the frost off the coil a few times a day. Most cooling faults come from these supporting parts, the fan, the heater, the sensor and the board, long before the compressor itself fails.

Almost every fridge has a sticker or metal plate inside, usually on a side wall or at the back of the fridge compartment. It tells a technician almost everything: the brand, the model number, the voltage and frequency, the type of gas the fridge uses and how much of it, and often the manufacturing date.

Take a clear photo of that plate before you call. With the model number we can check which thermostat, seal, fan or board fits, which saves time on the visit. The gas type matters too. Modern fridges often use R600a, a flammable gas used in small amounts, while older ones commonly use R134a. The two are not interchangeable, and a fridge must always be charged with the gas printed on its own plate.

If you cannot find the plate, look for a sticker behind the vegetable drawers, on the inside of the door frame or on the back of the cabinet. Send us whatever you can find and the brand, and we will help you identify the model.

Power cuts and surges are hard on fridges. When the supply returns it can arrive with a spike that damages the control board or the parts that start the compressor. Inverter fridges are the most sensitive, because a board sits between the plug and the compressor.

A good voltage guard, also called a fridge guard, delays the power coming back for a few minutes and cuts it if the voltage is too high or too low. It costs far less than a board repair. Choose one rated for the fridge, plug the fridge into it directly and avoid sharing the socket with a heater or an iron.

After any outage, wait a few minutes before switching the fridge on if you do not have a guard. Keep the door closed during the cut. A full fridge holds its cold for several hours if it is not opened, and a full freezer holds it for longer. Do not keep switching the fridge off and on at the wall; it puts strain on the compressor.

Bacteria multiply quickly above about five degrees. If the fridge side is warm, move milk, meat, fish and cooked food to the freezer or a cool box with ice, and keep the door closed as much as you can. If the freezer is still frozen, do not open it more than you need to.

As a rule of thumb, fresh meat, fish, dairy and cooked leftovers should not stay in a warm fridge for more than a few hours. Food that has thawed and warmed should not be refrozen if it has been warm for long. When in doubt, throw it out: a repair is cheaper than being ill.

Medicines that need refrigeration should be moved to a cool box and kept as cold as the label asks. If you are not sure whether something is still safe, check the instructions on the packaging or ask a pharmacist.

Many people ask for a gas refill as soon as a fridge stops cooling. In practice, a fridge uses no gas. It circulates the same sealed charge for its whole life. If the charge is low, the fridge has a leak, and a refill without finding the leak means paying again in a few weeks.

Most cooling faults are something else: a blocked air channel, a stopped fan, a dirty condenser, a failed defrost heater, a worn door seal, a start relay, a thermostat or a board. These are found with a few tests, and they are usually cheaper to put right than a gas job.

When the tests point to a leak, we find it first, usually at a joint, a pipe that has rubbed or a corroded coil, repair it, pull a vacuum to remove air and moisture and then charge the exact gas the fridge was built for, by weight. That is the only way a gas job lasts.

A freezer with thick ice works harder and holds less. If your freezer is not no-frost, defrost it when the ice is a few millimetres thick. Switch it off at the wall, empty the contents into a cool box, and open the door. Put towels underneath to catch the water.

Never use a knife, a screwdriver or any sharp tool to chip the ice. The cooling pipes run very close to the surface, and a puncture lets out the gas and ruins the freezer. A bowl of warm water placed inside speeds things up, and a hairdryer on a low setting held at a distance can help, if you keep it away from water.

Wipe the inside dry before switching on again, and give the fridge a few hours to cool before refilling it. If ice builds up again within weeks, the door seal or the defrost system needs a technician.