i have a 97 a4 2.8Q. my rear defrost doesnt work and i also have crappy radio reception on the stock head unit. when i hit the rear defrost button, the light on the switch comes on but its yellow, when all my other switch lights are green when they are turned on. (dont know if that matters or not). well i took off the rear trim panel on the drivers side to check for voltage for the rear defrost and i found a little green colored, rectangular shapped box about the size of a cellular phone. it has one wire going into it and a coax cable going into it. i figured the cable going into it is for the radio antennae. well i got 12 volts on the input wire when i turned on the defrost button so i know its getting power. it has 2 wires coming out of it that attach to a strip on the window (heating element i'm assuming), 1 power and 1 ground wire. the power wire has constant voltage on it whether i hit the defrost button or not and the ground wire was broken. well i thought this was the problem, so i put on an electrical connector and attached it to a little lip type thing on the heating strip cause i assumed thats where it came from. well it still doesnt work. so i have a couple of questions. 1) is the cable going into the box the radio antennae? and if it is, then why would the antennae and the rear defrost power go into the same box? and 2) am i missing something for the rear defrost? i mean, i inspected the elements and they look perfect. i couldnt find a break in the element anywhere so i dont think thats the problem. so am i looking at the right thing? or can the heating elements itself go bad? or did i connect the ground wire to the wrong spot? should i have just grounded it to the chasis somewhere? any help with this would be great.

 

The box is your antenna signal booster. It is powered off 12V constant. Your antenna are the two vertical strips embedded in your rear windshield. It does not power your rear defrost.

Now that you have reconnected your antenna check if your radio reception is better.

As far as your rear defrost, first check the fuse. I don't have my book here so I can't currently tell you where to locate the defrost connectors.