Engine mod 9 - car radio doesnt work

I just downloaded enginemod 9 today from svn and I made a car with a battery and a engine and i tried to hook up a car radio to it but when i got inside the car and started it up there was no sound coming from the radio. I also press R alot and nothing happened ether.

Can you guys help me?

[editline]03:23AM[/editline]

i think i got it, i had to press alt. Am i right?