I just bought an 01 civic used, and the A/C works perfect for around 30 minutes but then gets warm. It blows air fine, it's just not cold air. Any ideas what the problem could be?

 

Usually this is the compressor clutch gap, which can be adjusted by taking shim washers out to compensate for wear. I'm not sure if you can work on the clutch with the system charged on a 2001 though since it has that metal line to the compressor instead of two rubber hoses.

When it is not cooling you should check if the condenser fans are still running (engine running and A/C button engaged). If so the car is trying to pull in the clutch, but it can't because the magnetic coil gets weaker when it is hot, and now it can't work across the large gap.

 

That would be great! Because I don't think taking it back to the dealer that sold it to me would do any good... as soon as I signed the papers he threw all customer service out the window and became unhelpful and unhappy.

I'm stupid when it comes to this stuff... what do the condenser fans look like, and where are they located? Why would the A/C work again after continuing driving for 20 minutes and then re-turning it on?

 

Condenser fans are the fans under the hood behind the radiator. The cool both the condenser (located just behind the grille, in front of the radiator) and the radiator.

Also note the metal pipe going over the top of the engine on the drivers side and down to the compressor. This pipe should get cold while the A/C is on. Drive until the air goes warm then check whether or not the pipe is still cold, the condenser fans are running, and the compressor is engaged (drive plate on the compressor next to the pulley is spinning.) To tell the difference between compressor engaged or not, turn the A/C button on and off while it is still working.

 

I *hope* I found the issue. My A/C was working just fine yesterday... no 30 min shutoff and then on my way home at night all of a sudden all my gauges drop to 0 and my gauge lights go off, brake light gos on (brake is off), and driver side power locks don't work. The lights by the radio that are supposed to go bright or on when the lights are on went out or dim. Did some research and it looks like this is the multiplex control unit located in the dashboard fuse box. If spending 300 for a shop to do it or like 100 for me to do it will fix all of these problems that wouldn't be too bad.