Primary Value of Smart Dimension dimmed out

[jester11]

Hello,

Newbe to SolidWorks 2010. I am designing a part with a slot in it. The slot is supposed to be 30mm wide and I erroneously made it 40mm wide. Using the Smart Dimension tool I want to change the dimension. However the Dimension panel shows the Primary Value dimmed out and I cannot change it. How do I change the dimensioned value of a part.

 

[CorBlimeyLimey]

Is the dimension in the 3D models feature sketch or a 2D drawing view?

 

[rbpmc]

It may have turned into a driven dimension via a coincident relationship. Right click and show all relationships and delete the coincident relations that are locking it if this the case. Once the slot turns blue then you may able to change the width via a dimension.