Bad tune-up...

A blow drier may work - never tried one. I use a cigarette lighter and wave it under the shrink tube until it shrinks completely. Be careful not to get it too hot or it will melt. A quick bit of practice and you'll figure out the right speed and distance to do the job perfectly. If you've never used shrink tubing, you're gonna have a ball. It's one of those simple minds, simple pleasure things - it's just neat to watch it shrink down and conform to the item inside it.

blow dryer if it's warm enough, heat gun much better. Lighters and torches work if you are **very** carefull. I'd try a high intensity lamp before a flame. The quartz lamps put out quite a bit of rdiant heat. A reflector like a piece of foil will block heat from other plastic while the tube shrinks.