Fridge: basics

Know which fridge it is

ABSORPTION (Norcold, Dometic 2-way and 3-way): no compressor. Heat from an LP flame or an electric element boils ammonia in a sealed cooling unit. Must be level. Slow to cool (8 to 24 hours).

12V COMPRESSOR (Dometic, Norcold, Furrion and others): a small compressor and a controller. Needs strong 12V or 120V. Cools fast. See FRIDGE: COMPRESSOR.

Residential: plugs into 120V, often runs from an inverter. Treat it like a home fridge, but check the inverter and voltage.

Absorption: 5 checks first

Check the maker's recall lookup with the model and serial number

Level: about 3 degrees side to side and about 6 front to back (confirm for the model)

Back vents and roof vent clear, vent fans running if fitted

12V good at the board (control power)

Door seals good, door closes, door switch works

Which heat source works?

Run it on LP, then on 120V. COOLS on one only: the cooling unit is likely fine, the other heat source has the problem. NO COOLING on either: the cooling unit is likely failed, OR the board, thermistor or airflow is bad. Prove the heat first (burner lit and stable, element hot and drawing amps) before you blame the cooling unit.

LP side

Burner lights and stays lit. Dirty burner tube, rust flakes in the flue, a weak electrode or a poor flame sensor are very common. Clean with a soft brush and compressed air. Check LP pressure with a manometer while the fridge burns (about 11 in W.C.).

120V side

Measure the element resistance with power off. Compare to the label: ohms is about 120 x 120 divided by watts. A 300 W element should read about 48 ohms. Open or far off: replace. Check amps with the clamp. Check the thermal fuse in the heater wiring.

Controls

A thermistor (temperature sensor) in the fridge tells the board when to heat. A failed thermistor can leave the fridge off, or running nonstop, or showing a code. Check it with a meter: ohms should change smoothly with temperature.

A bad 12V supply makes boards act dead or throw odd codes. Check voltage and ground at the board first. Norcold wants above about 10.5 V.

Full-run performance test (proves the cooling unit)

Put a thermometer in a glass of water in the middle of the fridge. Run the cooling unit full time with the thermostat at max (or the thermistor disconnected to force it) for 6 to 8 hours.

Standard target: a 3 to 6 cu ft fridge in 90 F air should reach 43 F or colder. An 8 cu ft fridge in 110 F air should reach 43 F or colder. The freezer should reach 12 F or colder.

If it fails this test with good heat, good airflow and level, the cooling unit is weak or failed.

Signs of a failed cooling unit

Yellow or green powder near the boiler, an ammonia smell, a rattling or gurgling that stops, no cooling in either mode with proven heat, a hot boiler but a warm fridge. Replace the cooling unit or the fridge.

Ammonia smell, soot or burn marks near the burner: stop and ventilate. A leaking cooling unit is a safety issue.

Hot weather, frost, other

Hot weather: vents and fans, shade, a fridge fan kit. Frost on the fins: weak seal, door left open, or humid air. Freezer cold but fridge warm: low flow of cold air, a stuck baffle, or overpacked.

Do not tip the fridge past what the maker allows. Never lay a cooling unit flat unless the maker says so.