There are several reasons an A/C clutch will not engage.
There is a pressure switch located in the system that monitors coolant pressure. This switch may be malfunctioning. You can test this by jumping the connection at the pressure switch. If the compressor starts, you either have low pressure in the system or the switch is bad. WARNING: DO NOT USE THE A/C WITH THIS PRESSURE SWITCH BYPASSED. IF THE PRESSURE IN THE SYSTEM DROPS, THE A/C COMPRESSOR WON'T GET LUBRICANT AND WILL FAIL.
There may be a leak in the system. You may have added coolant to the system, but it may have leaked out again. If you simply add coolant to the system without repairing any leaks, to coolant will leak out again.
You may have used the incorrect coolant in the system. This is unlikely as the old style coolant has not been available foe several years.
The system may have been incorrectly serviced. If the system was completely empty, there could be air in the system. If any of the fittings in the A/C system were taken apart, there will be air in the system. This air must be removed by vacuum before the coolant can be installed. This is usually done by a certified A/C professional as this requires specialized equipment.
The coolant used in the A/C system also contains lubricant. If the A/C compressor was used without lubricant, the compressor may have failed.
This is a 9 year old car. The A/C compressor may simply be worn out.
