Horrible Clicking Sound
 

Whenever i turn my a/c or heat on i get this horrible clicking noise like the a/c clutch is getting engaged and then the rpms drop a bit (it sounds like you put it in drive but your in park) then you hear the click again and the rpms come back up and it sounds like a normal idle again. :td:

Most likely low refrigerant, causing the clutch to cycle. Does it do it on vent mode, A/C should not run on that setting.

oh i forgot to mention that it all started happening after i put new refrigerant in! and it does it even when i turn defrosters on...basically whenever the fans are spinning

That seems odd, A/C shouldn't run in vent mode. It does in all others though. What kind and how much was put in?

the whole can ( it was completly empty) and it makes the noise when i turn the heat on,i wont even touch the a/c. if i can ill post a video

One of those small 6oz cans? The system requires 2lbs, which is over 5 of those cans.

It sounds to me like you should take it to a shop with the correct equipment to correctly fill the system on your truck.

If it was actually completely empty to no pressure, you may need a new filter/dryer as well.

you say the system was empty, if you opened the closed system it will need to have a vacumn pulled on it before ya can add the refigerent

That happened on my truck in both underfill and OVERfill conditions. Time for professional vacdown.

whats your low side pressure at running the compressor and when not?