How do i adjust the tension of my up and over Henderson garage door with overhead spring?

Question

How do i adjust the tension of my up and over Henderson garage door with overhead spring?

Answer 1

At the end of the spring there is a cap that has two allen screws that lock onto a shaft to keep the tension in  the spring.There is also a hole in the cap. I insert a screwdriver into the hole to support the tension then undo the allen screws and wind in some more tension and re-tighten the screws