I have a 3 way dometic fridge, 12 years old, it seems to be struggling in spring and summer. How can i check it ?

If your Older Dometic 3-way fridge is underperforming during warmer spring and summer months, it’s a common issue — but one that can often be diagnosed and improved with a careful approach. These fridges can be sensitive to both ambient temperatures and internal issues, so here's a checklist of what to inspect first before replacing any components like the thermostat.

✅ What to Check First When a Dometic 3-Way Fridge Struggles in Warm Weather

🔧 1. Airflow Behind the Fridge

Poor airflow is one of the most frequent causes of struggling absorption fridges.

• Remove the exterior vent covers (upper and lower) and inspect the cooling unit and chimney.
• Check for dust, spider webs, or insect nests that could block vents or the flue.
• Ensure nothing is obstructing air circulation around the condenser fins or chimney.

Tip: Warm air must efficiently rise and escape through the top vent, it effectively a chimney, cold air comes in the bottom heats up and actually rises via convection and out the top vent — if not, heat lingers and reduces fridge efficiency.

Remember: A fridge doesn’t put cold into the interior cabinet it actually sucks so much heat out that the fridge becomes cold. So, if the fridge can’t throw the heat away at the back the fridge interior won’t become cold.

Adding fans to the back of your fridge won’t automatically help, (we have seen too many fans actually prevent proper cooling). Extra ventilation from fans and shade covers on the fridge can help overcome poor or incorrect installation. What we are wanting to check is that the heat in the back of the fridge is actually escaping via the vents, the cabinetry on the side of the fridge should not be getting warm, if it is then you need to improve the ventilation. Consider adding a fridge vent fan kit to boost airflow — we stock several 12V versions specifically for Dometic fridges that can improve cooling performance (they must operate on a thermal switch otherwise in cooler weather that will stop the fridge cooling correctly).

🔍 2. Is the Fridge Level?

Absorption fridges rely on gravity and convection through to the heat exchange fins on the top rear of the fridge to function properly. If your caravan is not level, refrigerant can't circulate properly.

Use a spirit level and check:

• The spirit level should be placed on the freezer floor.
• Side-to-side, use your jockey wheel to raise and lower the level, get this really accurate
• Front-to-back, this is harder you need to use levelling ramps - luckily the fridge is not as sensitive front to back.

Below 30 degrees ambient if your van is level enough for you to sleep then it’s level enough for your fridge to work. Over 30 degrees you need to make sure the fridge is completely level.

Here is a great tool to help you level your fridge.

🔥 3. Thermal Efficiency Testing

Place a thermometer inside the fridge. For testing we want the fridge completely level, not close to level, but spirit level in the freezer level.

Let it run for at least 12 hours on 240V mains (we use mains power as we know it is very consistent, gas performance can vary or need adjusting).

You're aiming for:

• Fridge compartment: 3 to 5°C 
• Freezer (if fitted):  -10°C or better, Deep Freezing is -18 or better (some fridges are not actually designed to Deep Freeze).
• If temps are much higher, go through the remaining checks.

🧯 4. Gas Burner & Flue Condition

If you're using gas:

• Remove the lower vent to access and inspect the gas burner area.
• You might see soot, rusty residue, or cobwebs.
• Clean the burner jet and flue tube using a soft brush and compressed air.

Also check that:

• The flame is blue and steady, not yellow or flickering.
• There's no carbon build-up in the chimney (which acts like a heat-shield and ruins the absorption process).

This is starting to get technical here and it maybe better to book your van in with a professional - our team are very familiar with this work (after all we used to be “Caravan Refrigeration Services”). The Gas Regulator Pressure may also need checking to ensure the flame is operating correctly, you can not tell from just looking at it.

💡 5. Fuel Source Performance Comparison

Test all three modes (one at a time):

• 12V (DC), Maintains temperature while driving, Mostly doesn’t get great supply from the tow vehicle, so its purpose is not to cool the fridge, but to maintain the temperature you left home with. Doesn’t use thermostat.
• 240V AC, Best mode for effective cooling and testing, works most like your household fridge.
• Gas, Slower but consistent cooling, Needs clean burner + good airflow.

If it performs poorly on all supplies, it’s likely a cooling unit issue. If only 240V is bad, inspect heating element & thermostat. If only performing poorly on Gas, then it can be the Gas Regulator, Thermostat or Dirty Jet.

🔍 6. Heating Element Function (Electric Modes)

For 240V and 12V modes:

Access the rear panel:

• Check that the heating elements (there are two: one for 240V, one for 12V) get warm when fridge is powered on.
• Use a multimeter to test element resistance:

• Typical: around 70–100 Ohms for 240V
• Open circuit = burnt-out element

If the 240V element doesn’t heat up, replace it — we can help source the exact element depending on your model.

📦 Recommended Checks

• Thermostat test:  a failing thermostat can cause temperature inconsistencies (especially on 240V or gas).
• Foam insulation sagging (rare but possible with age) — if warm spots form inside fridge, insulation might be separating.
• Ammonia smell or yellow powder: Signs that the sealed cooling unit is leaking — fridge needs replacing (some models we can actually replace the cooling unit saving about 1/2 the cost of a new fridge.

🧰 Recommended Fixes for Hot Weather Use

If your fridge checks out but still struggles in heat, consider:

• Fridge vent fan kit, dramatically improves cooling with extra airflow
• Internal circulating fan, helps distribute cold air inside the fridge
• Shade the side of the van, where the fridge is located
• Only place pre-cooled food in the fridge and avoid over-packing, allow airflow between items

If you need to book your van in with us to get your fridge working, give us a call on 03 9574 1900 or email us at info@everythingcaravans.com.au.

See our blog on cooling your fridge before travelling here.