I recently install a pioneer head unit and now the aerial doesnt go up or down could the relay for the aerial require more power the the radio puts out that is 300ma at 12v thanks in advance

 

Relays are usually in the 80-100ohm range so resulting current is in the 150mA range. I changed to a generic Alpine unit a while ago and it worked OK with no mods.

You measuring 12V at the relay and no operation? other possibility is a blown fuse to the relay but you would have lost cabin and rear door lighting also if that was gone.

 

Are you sure the connection (radio to antenna motor ) is secure.... The radio triggers the motor action.

 

check which wire from the new radio is the power antenna wire, it may be a Blue wire The instructions for the new radio installation should tell you.

It connects to the White wire at the car's radio power harness.