Today, I tried to turn the A/C on; but no luck in my Impreza OBS. It just blew the normal warm air...

What went wrong?

I turned on the fan (to 4), pressed the A/C (green lighted on), and the compressor was not moving. I saw some red/rusty powder around the clutch section of the compressor.

Last year, I remembered that I need to charge the system as recommended by the mechanic in August 06 and the weather started to drop and no need AC that much; but I ended up forgot to do so. And since Sept 06, I did not turn on AC until today.

Please let me know what I should do to check the system? I looked in the relays under the hood, the black relay seemed to be fine. Also, when I turned on the A/C button, there is no voltage drop (that is from the lighter plug which I have a voltage reader plugged into it to just test it).

Please help.

If theres no refrigerant the compressor wont engage. Try putting this in the right forum and I bet youll get more answers.

If it needed a charge in August it still needs one now. There is probably a leak in the system and once the pressure gets below a predetermined point the compressor will no longer engage.
If the system has been empty and open to atmosphere for any significant period of time it will need more than just a recharge for good long-term results.

I recently had to have a couple O-rings replaced in my system to fix leaking refrigerant. Same situation as yourself, one day the AC just didn't work. My car is getting old.:p

I recently had to have a couple O-rings replaced in my system to fix leaking refrigerant. Same situation as yourself, one day the AC just didn't work. My car is getting old.:p

Same here, but I didn't check if my ebay TMIC rubbed a hole.

Probably got a leak someplace. Pepboyz or Autozone can pump colored fluid through your system to find the leak. Plus, they will only rip you off a small bit.

A/C is for fairy men. God invented windows for a reason. The cheapest way it increase both speed and gas mileage in a already heavy small car is to take out weight. Said weight being your A/C system. I did this once in a Mark II Golf and it was a much funner car as a result.

The mechanic pump the dye into the system. It seemed that the leak is so so so small. From the mechanic's point of view, it consider as nothing. There goes my 30 bucks. and now the AC is cold. but also the weather is dropping back to 30 degree F....