AC Making Noise

Whenever I turn on the AC, turn it to defrost or recirculate I get a loud sort of solenoid clicking sound under power. It still blows cold.

I bought more refrigerant after reading some posts here that mentioned the pressure might be low. However the guage it came with said the pressure was normal. It was at about 40 on the guage.

Anyone have any ideas?

Could it be the clutch on the compressor? How could I check that?

Thanks!

Is that clicking noise underdash? If so, likely a bad recirculation "door" motor, common on these vehicles. You can unplug its harness once it's in the position you want, if you don't need to to cycle.