If it doesn't work for your rar file, then you may look at topics where experienced users can help you and give a solution or last method is suitable only when your .rar archive is fully crashed
RAR Open File Tool
The process of doing this is as follows:
1. Right click on the RAR files and from the list, click on the extract files option.
2. A window will appear showing where a folder can be selected and where it may be saved.
3. Choose the check box which gives the option ‘Open Broken file’.
4. Click OK at the bottom of the window.
5. A warning will pop up but it should be disregarded at this point.