The compatibility of the Pioneer DMH-A240DAB car radio with a 2007 Audi A3 depends on a number of factors, including mounting space and electrical connections.

- Mounting space: The radio is a 2-DIN model, which means that it requires a standard 2 DIN mounting space. You should check whether your 2007 Audi A3 has a compatible mounting space.
- Electrical connections: You will probably need a specific wiring adaptor to connect the car radio to your car's electrical systems. An Audi A3 adapter kit may be required.

It is recommended to consult a professional or check the specifications of the car radio and your car for a correct and trouble-free installation.