Hi. I'm using a Badger Khrome Renegade. It is very clean. However, when I use it the air is on free flow. It does not spray, unless I pull back on the trigger. The only thing that I can think of is a problem, with the valve assembly. Should I buy a new one or is there another solution?

Replacing the valve is certainly an option that will work, but the valve can be disassembled and repaired also. There is likely a piece of debris embedded in or jammed between in the seal and its seat There could also be a cut. Troubleshooting the valve will take longer, but cost less to fix. Your time and wallet should be the judge of how you approach the repair.

You could also have paint dried in the area around where the valve pin enters the airbrush body. When you remove the valve, I recommend you clean that hole really well as it only takes a tiny bit of residue to stop things from working.
Cheers
Paul H