what type of freon do you need for a 2005 mercury montego and where do put it

If you don't know where to put it you should not be doing it. It simply isn't safe. The car came with R134a refrigerant. Typically you need a certification to purchase and replace refrigerant.

NO.you DO NOT need a certification to buy R134a or to put it in yourself!most of the cans come with a gauge and hose on them,and the quick connect fitting on the hose will only fit on the LOW side fitting only.you have a HI side and LOW side only,and the quick connect fitting will not fit on the hi side.been a long time,hope you got it working in 3 and half years!