Electrical issues

The Wife has a 2007 Caliber, Recently the rear wiper quit working. My Dad pulled it into the garage, and before turning the car off he tried the wiper, no go. When I got there I started the car, wanting to see myself, the car ran like shit, idle was varying 700rpm, (surging) Turned car off, re-started, it started good, tried the wiper and the car started surging again???? I took the rear wiper apart, motor looked good, clean, didn't see nothing that stood out. there is power getting to the motor, as I did get a zap testing it. Put everything back together. Then when we were leaving my parents I could hear her car surging, when she shut the heater fan off it idled good, turn fan back on it surges at idle. My Wife then told me its always done that. That doesn't seem right to me? got to be an electrical fault some wheres.



Anyone got any ideas????