I have tips in good shape, but the valve isn't working too well. Even if there is gas in it I have to overfill it before each use to get it working again. It has also lost most of its temperature control. I either have to run it full blast or it just quits.
Try cleaning it first. They not usually mechanically complex, it's probably just buildup inside the valve body. Open the valve up as far as it goes and try using compressed air from a can of air to force a cleaning sollution through the valve body, alcohol or vinegar should work okay. If there's any way to completly disassemble the valve to clean it that would be ideal.