How to operate the Truma Frost Control system

Applies to: Comfort Standard, Active Bunk, Active Pop-Top, Active Standard, California Grand

Symptoms: Water draining under the vehicle, no hot water in the taps or shower

What's happening

Your camper has an anti-frost system that automatically drains the boiler's water tank when the outside temperature drops below 5°C, to stop the water inside from freezing. When it activates, water drains out through a valve under the vehicle. This is normal, protective behavior, not a fault.

How to close the valve and refill the boiler

1. Check that the blue rotary switch is set to "Operation" and properly engaged.
2. Press the blue push button into the "Closed" position. Make sure it clicks into place.

Temperature matters: You can only close the valve manually and refill the boiler if the temperature at the valve is above roughly 7°C. Below that, close the valve, but first switch on the vehicle heater to warm the interior before refilling.

Valve positions, for reference:

Rotary switch position “Operation” → System is active and monitoring Pushbutton position “Closed” → Valve is sealed, boiler can refill Pushbutton position “Drain” → Valve is open, boiler is draining Drainage socket (routed outside through floor of vehicle) → Routes water outside through the floor

Where to find the valve

Active Bunk, Active Pop-Top, Active Standard, California Grand Located under the rear seat
Comfort Standard Located outside, in the water tank compartment

Preventing it from triggering unnecessarily

• Keep it warm: Maintain enough heat inside the camper to keep the valve from activating in mild cold.
• Check it periodically: Inspect the valve during your trip to make sure it's functioning correctly.