Just re-gassed a/c in my 04 civic.
A/C works fine but loud hammering noise is comming out from somwhere. would that be a compressor ? does anyone have any ideas ?

 

It could be overcharged. What are the operating pressures (low and high side)? How much did you add? The total capacity (starting from vacuum) is probably less than 20 oz, look for a sticker under the hood.

 

No clue. done it in a citroen garage. but noticed while driving that noise is adequate to the revs. higher revs more bangs.
System was empty and not used for at least a year. does it matter ?

 

does it stop if you turn the a/c off? Your fan might be bad and hitting the compressor.

 

it does stop when a/c is off. it stopped few times when on as well but just for few sec.

 

I don't know if this is the case with yours, but my blower motor has gone to hell and the symptoms sound identical to yours. I'm rockin a 91 though so obviously we have some differences, might be worth checking out though especially considering it was empty for a year. Good luck.