If your refrigerator is not turning on, or seems to have no power at all, make sure it's plugged into a wall outlet. If it is a refrigeration unit that uses a disconnect, or an external powering unit, check the power in the unit. It is a good idea to see if all the wiring for the ground wires is correct as well. Improper wiring can cause short circuits. Next, check the cabling and wires to see if anything is loose, damaged, or missing. If the unit has a power switch, check to make sure this is set to the on position. If none of these troubleshooting steps work, use a voltmeter to check that the unit is getting power.
If your refrigerator unit is freezing up, with excess ice collecting on pipes or inside the unit, check that the evaporator fan is running. Its location is different for each refrigerator model, so check your owner's manual for the location. If there is ice on the evaporator, melt it by turning off the unit. In the evaporator, make sure all the coils are clean, and that the drain is free of debris. Clogs and excessively dirty coil lines will not allow the refrigerator to draw out excess liquid. If the evaporator pipe is freezing, check that there is a sufficient charge to the evaporator by using a voltmeter, and check your readings against the specifications of the unit, found in your owner's manual.
A compressor creates the cold air used to freeze or chill food. If it's not working, your unit has power but no chill. If you believe the compressor has malfunctioned, check to see if it's running; it should make a humming noise. If it is dead, check the compressor with a voltmeter for amperage. If it is making a start-up noise, then a loud clunk, the compressor engine is attempting to start, but is resetting before it can do so. This may indicate an engine issue. If it is running hot, the unit may be overloading. Check that the compressor fan is running and clear of debris. If it is, there may be a malfunction. Have a service technician check it out.