A 12V camping fridge runs on one of two systems: a compressor that actively pumps refrigerant, or an absorption cycle driven by heat from gas, 12V, or mains power.
A compressor fridge holds its temperature off-grid; an absorption fridge holds it only while you keep feeding it heat. That single difference decides which unit survives a weekend on battery and which one flattens your truck battery before lunch. This piece covers how each system moves heat, the exact current draw on a real ARB compressor unit, and the wiring mistake that voids the point of buying one.
How Does a Compressor Fridge Cool on 12V DC?
A compressor fridge uses a DC motor to push refrigerant through a sealed loop, and the evaporator pulls heat out of the cabinet. It behaves like the fridge in your kitchen, just running on vehicle voltage instead of a wall outlet.
Power flows in cycles. Once the cabinet hits its set temperature, the compressor stops, and the draw drops to near zero until the thermostat calls for cold again. ARB’s service manual lists models 10800010, 10800020, 10800030, and 10800040, with one ARB manual giving a rated current of 7.0 A at 12 VDC and 3.0 A at 24 VDC for a 47-litre (49.7-quart) unit — figures measured while the compressor is actually running, not averaged over an hour.
Two practical consequences follow. First, compressor fridges work off-level, so a sloped campsite is a non-issue. Second, a compressor fridge can run on mains power too:
How Does an Absorption Fridge Differ?
An absorption fridge has no compressor at all. A heat source — a gas flame, a 12V element, or a 230V element — drives a chemical cooling cycle built on ammonia, hydrogen, and water. Dometic’s RMD line is a three-way design offering 12V, 230V, or gas operation, with automatic energy selection (AES) on some versions.
The flexibility is genuine.
If you are choosing between the two formats for a vehicle build and want a shortlist sorted by size and power source, this tested roundup of camping fridge models covers the practical options.
| Feature | Compressor Fridge | Absorption (3-Way) Fridge |
|---|---|---|
| Cooling method | DC compressor circulates refrigerant | Heat drives ammonia/hydrogen/water cycle |
| Power sources | 12/24V DC, plus AC via inverter | 12V, 230V, or gas |
| Power behavior | Cycles on and off with thermostat | Draws continuously while running |
| 12V while parked | Fine on a charged battery | Not recommended — drains battery |
| Level ground needed | No | Yes |
| Example spec | ARB 47L: 7.0 A at 12 VDC | Dometic RMD: 170 W at 12V |
| Best for | Battery-only off-grid trips | Gas or shore power available |
Which Wiring and Use Mistakes Cost You?
Most failures trace back to treating two different refrigeration systems as one product category. The name on the box says “12V fridge” either way, but the behavior underneath is not comparable.
- Assuming every 12V fridge is a compressor unit. A three-way absorption model running on 12V and a compressor unit running on 12V have almost nothing in common electrically.
- Running an absorption fridge on 12V while parked.
- Ignoring leveling on an absorption model. Compressor fridges do not care about angle; absorption units do.
- Wiring a compressor fridge straight to the control unit. ARB’s service manual states supply voltage should be applied through the DC power socket in the back of the fridge, not directly to the compressor control unit.
ARB’s connection guidance is specific: plug the 12/24V power lead into the DC power socket on the back panel, then connect the free end to a 12V or 24V DC supply.
Which One Should You Run?
Choose a compressor fridge when battery power is your main source and you want cooling that holds temperature without a flame, a gas bottle, or a level pitch. Choose an absorption fridge when you will usually have LPG or shore power and you value running on whichever source is available, with automatic energy selection doing the switching on supported Dometic RMD versions.
Absorption still earns its place in rigs where gas is the default and 12V is only a travel-mode backup.
FAQs
Can I leave a 12V compressor fridge running overnight?
Yes, provided your battery bank has the capacity. A compressor fridge cycles on and off, so its average draw is far lower than its peak rating. ARB’s 47-litre unit is rated at 7.0 A at 12 VDC while running, but it only pulls that figure during cooling cycles, not continuously through the night.
Why is my absorption fridge not cooling on 12V?
Switch to gas or 230V, or run the engine, to restore it.
Do compressor fridges need to be level?
No. A compressor fridge circulates refrigerant with a pump, so it works off-level without issue. Absorption fridges are the ones sensitive to leveling, because they rely on gravity-driven circulation of ammonia, hydrogen, and water inside the cooling unit.
References & Sources
- Thetford. “Absorption vs 12V Compressor RV Fridges.” Explains the operating difference between compressor and absorption cooling and the 12V caveat for absorption units.
- ARB. “ARB Classic Fridge Service Manual.” Lists fridge models, capacity, rated current at 12/24 VDC, and the power-socket connection requirement.
- ARB. “ARB Fridge Freezer User Manual.” Documents 12/24V DC and 100–240V AC operation and the DC power lead connection steps.