Once the engine is turned on I am getting air blown in through the rear vent to the drivers side.

This has started happening in the last week and just after I had someone attempt to replace the original Japanese stereo. Does anyone know why this is happening or to switch it off 

Well they have rear climate control, which can be controlled from the front climate panel, or from the one in the rear.

 

Changing the stereo shouldn't affect its operation as it's not tied into the sound system at all.

I have red recently that it's wired behind the centre console . I had someone in there there playing with the wires just last week and now I have constant air blowing in the back ...I have switched off the controls on the centre console yet I still have this air blowing through the rear vent .