It's important not to confuse two different things: the cabin air conditioning (the dashboard unit, which runs off the engine, just like in a car) and the living area air conditioning (the roof unit, which cools the habitable space when you're parked up). Here we're talking about the cabin unit, which also needs maintenance to cool properly on hot summer drives. Here's a clear explanation.
How it works and why it stops cooling
Cabin air conditioning cools using a refrigerant gas that circulates in a closed circuit. Over the years, that circuit gradually loses gas (this is normal), and eventually it stops cooling well, or at all. That's why the classic symptom is "the air conditioning doesn't cool like it used to": it's almost always down to low refrigerant gas, which needs recharging.
The key maintenance points
- Gas recharge: when it loses effectiveness, a garage checks and recharges the refrigerant gas (and checks for any significant leak). This is the most common fix.
- The cabin (pollen) filter: if it's dirty, airflow suffers and cooling gets worse, along with letting in dust and odours. Replace it at service intervals.
- Cleaning and disinfecting: the air circuit can build up bacteria and cause bad smells (the classic musty smell when you turn it on); there's a cleaning/disinfection service for the system.
- Run it occasionally in winter (for a few minutes): it keeps the circuit lubricated and in good condition.
The other air conditioning: the living area
Different again is the living area air conditioning (roof-mounted), which cools the habitable space while parked and uses a lot of electricity (usually needing a campsite hook-up or a large electrical system). To fight the heat while running on battery, ventilation and insulation are the foundation, and solar plus a good battery help too (see your camper during a heatwave and the calculator).
In short
Cabin air conditioning cools using refrigerant gas that's lost over the years, so when it stops cooling it usually needs a recharge; also look after the cabin filter and have it disinfected if it smells. The step you can take today: if your cabin air conditioning isn't cooling well, get the gas recharged and the cabin filter checked before summer, and run it for a few minutes in winter to keep it in shape. Pair it with the maintenance checklist.