I got my Forester used a little bit ago and the AC didn't work. We've been fixing up little things one at a time, but I can't figure this one out. When I turn on the AC or defroster, it makes a loud buzzing, kind of like if you sped up a ratchet sound a lot and made it louder. It blows warm air from the AC when it is on regardless of the setting.
Your first post? Welcome aboard.
I'm guessing you have two distinct problems. For the buzzing sound, you probably have some debris in the fan duct, rubbing against the fan blades. Start by removing your cabin air filter. On a Forester, it's a PITA, but do-able (search this forum for how-to threads). Basically, you remove your glove box completely and the RH dash segment (after removing screws, it pulls straight out off of a snap-post). The filter is behind a small black plastic door behind all of this mess.
If this is the original 2004 filter, you might wear a bio-hazard suit. You're in for a surprise (maybe not of the pleasant kind). Don't be surprised to find a tree growing in the duct complete with alien life forms living in the branches. Regardless, while the filter is out, reach around in the duct work and try to extract whatever is making the noise. I like TYC cabin air filters off eBay. Or buy these pricey little items at your friendly auto-parts store.
As for the 'no cold air' problem, you're probably low on freon or else your A/C clutch is shot. A shop can check your freon level (easy). If the compressor clutch is not engaging or holding, my vote is to replace the whole compressor with a rebuilt unit. You can try to repair the clutch but... replace the whole unit. While you're at it, check you A/C idler pulley (Gates makes a better-than-OEM- and-cheaper! replacement). Also, look at your A/C and accessory belts - they may need changing as well.
