Hi Silva,
To execute In house Repair process, you have to initiate through service notification
In the service Notification, enter the Material + serial number which will automatically determine Equipment ( provided if you have already created Equipment with material and serial number)
now create Repair order using Action box and repair order can be maintained with serial number in VA02
---> click on line item-->Extras--Technical objects and assign serial number, in this way you are linking Equipment to Repair order
thanks
santosh