i just trtied replacing my arm i found out why the arm doesnt wipe. Part of the key is using VOLVO OEM arms, you can get refils anywhere but if you look at the volvo spring setup its totally differnt from even the bosch excel at pepboys. There is an additional spring piece on the volvo one. Also if your arms are volvo oem make sure those little clips that hold the refil are far enough apart to allow the refil to move a bit, if its tight the tension cannot evenly distributie itself over the whole window as the arm sweeps across and you end up with peaks and valleys in the refil leaving a unclean sweep.

Additionally the driver side arm has a wing which helps the arm deflect air and allow it to work better at highway speeds, this also adds weight which helps keep the blade down as well.