The AC was working last night but this morning no air comes out when I turn the AC on. I've read most of the posts regarding this issue but am still a bit confused on where to begin the diagnostics. Any help is appreciated!

 

Fan runs?

Compressor clutch engages?

Any heater control panel trouble codes?

Any multiplex control unit trouble codes?

 

Nothing inside the car comes on. I can hear the clutch engaging from inside the car.

 

The vent blower and A/C light don't work, but the compressor clutch engages??

What about the condenser fan?

 

2001 - 05 Interior fan won't run troubleshooting:

Locate the blower motor under the dash on the far right side. No need to take anything apart. There is a two wire plug on the bottom. Turn the key on and set the fan switch to high. Measure the voltage from each wire to ground, with the motor still plugged in.

Zero volts on both wires: Blown fuse, or bad relay (both in fuse box under the hood)
Battery volts on one wire, zero on the other: Bad blower motor.
Battery volts on both wires: Almost certainly it's a bad power transistor. Unlikely but possible: bad control panel or ground.

 

The light on the AC button does come on. I just went out and checked the condensor fan and it does not come on. I also cannot confirm that the compressor is coming on either. I thought it had before but nothing happened when I turned the AC on now. The engine doesn't idle up and I didn't hear the clutch engage.

 

Get the fan inside working first. The light in the button is a good sign that the control panel is not entirely dead. If the compressor does run without the interior fan, the evaporator will get cold really fast and that will cycle the compressor and condenser fans off.

 

Does the cabin vent blower work? I wasn't sure whether you meant no air blows or no cold air blows from the vents.

 

No air comes out at all.

 

Do the control panel test that Ron posted. If you get a code 12, get a voltmeter and do the test that I posted.