weird audi issues all from one thing on my tt!

[audia4cardad]

So my TT's radiator conduct unit went.

I had it repaired at £370.00

Got the car back and the air conditioning works warms up but now air only comes out of the left and right vent not middle vent.

The mechanic says he only touched the radiator unit not a/c nothing to do with him.

Anyone know what causes this with a/c and cost of repair?

I've now further to this just turned the car on and randomly got  a 'car battery low it will charge when you drive' it has disappeared but the only way i think the battery can be low is from the above issue..any help?