Fridge: compressor
How they work
A small DC compressor with an electronic controller, a condenser fan, and a thermostat sensor. It runs on 12V (some also 120V). It is fast to cool but fussy about voltage.
Voltage is the #1 cause
Measure at the controller, while the compressor tries to run
Compare to the battery. More than about 0.5 V lost means wire or connection trouble
Check fuse, ring terminals and ground
Wire gauge fits the run (thin wire to the fridge is common)
The controller has a low-voltage cutout to protect the battery. A thin wire can make the controller cut out even when the battery is fine.
Blink codes on the controller (Danfoss and Secop style)
1 blink|Battery protection cutout|Voltage too low. Charge the battery and fix voltage drop.
2 blinks|Fan overload|Check the condenser fan for jams or a short.
3 blinks|Compressor failed to start|Low voltage, locked compressor, or a pressure not equalized. Wait 5 minutes and retry. Check wiring.
4 blinks|Minimum motor speed fault|Often a restricted or failing compressor, or low voltage.
5 blinks|Controller overtemperature|Poor ventilation around the controller or compressor. Clear the airflow.
Blink code meanings can differ by controller and model. Confirm against the controller label or the fridge manual.
Other checks
Compressor starts then stops: voltage drop or low voltage cutout. Fan runs, no cooling: low refrigerant or a failed compressor (needs a certified tech). Constant running: bad door seal, dirty condenser, hot ambient, or a failed thermostat sensor.
Refrigerant handling needs EPA certification. Do not open the sealed system.
Keep going on refrigerators
Learn it
- Absorption fridges (gas/electric)
- 12V compressor and residential fridges
- Absorption fridge won't run on gas
- Absorption fridge won't run on electric
- Is it the cooling unit?
Prove it
- Fridge won't run on gas
- Fridge is warm after unplugging
- Fridge works on gas, not electric
- Fridge won't cool on anything
- Freezer's fine, fridge is warm