How do you replace this part?

A quick learner says:

date: 05-27-09

what is involved in replacing this part?

date: 06-04-09

The 15-086 is just the housing for the S180 sash support system. You will probably need to replace the spring that sits in this housing (see S180 coil springs). First, remove the window sash from the window frame (see instructions on this step). Take a look at the diagram of the Series 180 coil sash support balance system. You will need to unhook the top of the spring by unscrewing mounting bracket (there is a chance your window manufactured placed a shield or cover infront of this mounting bracket). After you unhook the spring you can take the housing apart to replace the spring and or housing.