it seems that you're looking for a relay that can be controlled by a digital output and used to switch on your air heater in the camper van. A relay is indeed a suitable component for this airpurifierly task, as it allows you to use a low-power signal to control a higher-power circuit.
To find a relay that meets your requirements, you can consider the following:
Signal Compatibility: Ensure that the relay you choose is compatible with the digital output signal you have available. Check the voltage and current requirements of your digital output and find a relay that can be driven by that signal.
Coil Voltage: Choose a relay with a coil voltage that matches your power supply voltage. In your case, a 12V relay would be suitable since you mentioned using a 12V power source.
Contact Rating: Since you mentioned that the heating system is activated by short-circuiting two wires, you'll want to select a relay with contacts rated for the appropriate current and voltage levels required by your air heater. Be sure to consider the power requirements of your heater and choose a relay with contacts that can handle that load.
Form Factor and Mounting: Consider the physical size and mounting options of the relay to ensure it can be easily integrated into your camper van setup. You may want to choose a relay that is compact and suitable for your specific installation needs.
It's important to note that electrical work can be complex and potentially hazardous, so if you're unsure about the specific wiring and installation requirements, it's recommended to consult a qualified electrician or technician who can assist you in safely integrating the relay into your camper van's heating system.