For your motorhome roller shades with a 3/4" diameter tube that have lost their locking function, replacing the spring inside the roller tube is the most effective and cost-efficient solution. We recommend the Replacement Spring for 3/4" Valu-Line RV Roller Shades, designed specifically to restore the locking mechanism and ensure smooth operation. This part is available at Elkhart RV Parts. Installing this replacement spring should resolve the issue without needing a full shade replacement. If you have any further questions or require assistance with installation, please feel free to contact us.