Service requests use Assignment manager to establish the owner assignment and all is good for newly created service requests, the 'Reassign owner' checkbox is set for each new record.

However when an SR is changed the assignment manager will not run, unless the user manually sets the 'Reassign owner' checkbox.  This requires the user to remember to do this which is not always the case.  Ideally this should set automatically if critical information about the SR is changed.

The obvious answer is to create a workflow that triggers when critical fields on the SR are changed eg priority, area, by using the 'before modified record saved' event, create an 'Update value' action to set the 'Reassign Owner' field to 'Y'.

Ordinarily this would work, except the 'Reassign owner' field is NOT available to the 'Update Value' action!

The answer is to clear the owner field and the 'Reassign Owner' checkbox will automatically be set.  But you cant 'Update value' to the Owner field to be null either!  So the trick is to 'Update Value' to the field 'Owned by ID' to '', thats two single quotes, see Image.

Simple but frustrating if you dont know how.