Replaced battery Dash gaughes instrument panel not powering or working help please.

I have 2003 a4 b6 1.8t fwd recently battery died and i replaced upon replacing it my instrument panel stop working. some of my idiot lights come on like the ESP and ABS and Air bag. my center screen still works and my mileage and clock still work but are not lit up and can barely see them. the speedo tech temp and gas gauge dont even budge and the instrument panel wont light up at all. ive check every fuse in the car is fine. new battery so its good, checked all the connectors and even wiggled the ones near the ecu where the wires from the instrument panel run too and it still wont power up the gauges light etc. im stumped i took it to my mechanic who is very helpful and knows alot about audis and he did a vag-com test and said that the instrument panel wasnt getting power so he couldnt do the test because it wasnt communicating with him. i can still operate the car no emob so far thank good and i dont wnat to trip that. my signals still work but not on the instrument pannel. upon disconnecting my instrument panel i notice that the blue connector on the left was doing anything when connected or disconnected so i assume this is the problem or part of the instrument panel internally is not working. so my mechanic is printing my a wiring diagram which i will get from him tomorrow. but my question is should i test the blue connector for power ? and if so then it means my instrument panel? my mechanic says there is a small transitor thing in the instrument panel that might have burn up and might need to be sent for repair or he has a micro sauter tool and may be able to fix if that is indeed the problem. another to note is when i disconnect my instrument panel fuse or unplug the blue cable from the instrument panel my heating/ac lights come on by themselves?? weird. any help would be appreciated because i dont know really where to go from here. thank you.