Fix My Fridge

Specialists in the repair and service of 12v & 24v truck, campervan & boat fridges

Fault finding - My fridge is too warm

If your fridge is too warm there are several possible reasons – the thermostat is not set correctly, the fridge box or freezer plate is iced up, the fridge or freezer compressor is only working intermittently, the door seals are poor or the door is not closing properly or the thermostat is faulty.

First check the amount of frost build up around the evaporator plate. Excessive icing acts as insulation and stops the plate from achieving the correct temperature, usually around -4?C to -8?C for a fridge and -20?C and below for a freezer. If there is significant ice build up defrost the fridge and freezer completely and then this should cure the problem.

If there is no sign of excessive icing, check the thermostat setting. Normally the higher the number the colder the fridge or freezer. Turn the thermostat to the highest number and check to see what effect this has on the temperature in the fridge. 

If there is excessive icing, or lots of water/condensation in the fridge it is likely the door seal is faulty or the door is not shutting correctly. Check the seal to make sure there are no tears or damage. If there is replace it. A good way to check the door is closing properly is to run some chalk around the fridge frame door frame, then close the door and open it again. If the seal is good the chalk will have transferred evenly from the door frame to the seal and be clearly visible right around it. If it is not, check the hinges alignment and adjust to get the door closing evenly once more. 

Having eliminated the potential causes above, you are left with two possibilities: 1. The fridge compressor is working intermittently or 2. The thermostat is faulty. In our experience it more likely to be the former than the latter. Intermittent faults are always the hardest to identify, but simply if intermittent it is likely to be a loose wire or low voltage. 

First check the wiring of your thermostat to the controller on the compressor.  The two thermostat wires connect to the C and T terminals on the control box.

Does the problem occur mainly when running the fridge just from the battery (with no hook up or battery charging) or after the battery has not been charged for several hours. If the answer is yes, then the problem is almost certainly low voltage. To start the compressor requires a considerable jump in amps for a milli second (start load). This is usually well in excess of 8 amps and any resistance in the wiring due to a loose or poor connection will cause the voltage at the compressor to drop. If the voltage drop is sufficient to fall below the 10.5v (23v on a 24v system) a built in cut-off within the compressor’s controller will stop the compressor from starting.  Check your wiring thoroughly, before changing any other parts. If the problem is not related to the power in the batteries check the thermostat connections. 

Only once you have thoroughly checked your electrical wiring should you consider changing the thermostat.

This article was writen by Zeb Elliott of www.fixmyfridge.co.uk a division of Penguin Refrigeration Ltd