I would check the wiper motor first. Maybe try replacing that and see if it gets better. If that doesn't help, I would just replace the wire instead of trying to find the short. Grease, dirt, ...

This week, on The Best of Car Talk, fuses keep blowing in Allison's car. Can it be fixed or would investing in her local auto parts store be a better choice? Meanwhile, Nat's Saab keeps running away ...