Changed radio no power steering

[Theo12848]

Change the radio on my audi a3 2.0 fsi 2004 and got the ignition feed from the park assit and garage door opener fuse as it was not being used and after the power steering wudlbt work. The diagnostics says "gateway - no communication with electrohydraulic control modual (j500) " 
The next day I took all of the sub frame of and gave the steeing rack connections a clean and did the same with the box under the steering wheel. Then turned the steering from one lock to the other and the powwe steering worked, tured the engine of left it for 5 mins and no power steering. The next day I reversd in full lock restarted the car and had powersteering drove for about 30 mins turned the engine off and back on again it stI'll had power steeing left it off for an hour no power steering.
Any one have any ideas

Did I blow something when I used that fuse
Do I new to calibrate or program the steering
When doing the radio change the battery went very low

Any help is really apreciated

[Trevor]

It would be worth checking the battery condition before proceeding further as this could cause the symptoms you're describing...and if there is any doubt then worth changing the battery especially this time of year when there is more demand on the electrical systems.

I think also that if it isn't the battery at fault, it may be worthwhile removing the radio connection just to see if that makes a difference.

Let us know how you get on with it.

Cheers   Trevor