Heat guns wear out. If your an avid builder, and the heat gun has lots of hours on it, then you might need a new gun.

There was another guy recently--I think it was Q&A forum--had the same problem, and he bought a new heat gun. He was a lot happier after he purchased the new gun.

Can't hurt. They're cheap. I got one free from Tower a few months ago. They were offering a free heat gun to Saver members who made a purchase over $100. I snatched one up real quick. Tried to do it again a week later with another big order, but they only let you have one free. [&o]