I have just replaced the wiper motor on my 68. When I push the knob so as to use the washer it works fine. But it will not work on low or high. This is the second motor ive put in. I sent the first one back thinking it was faulty. They told me that the wiper motor would either work or it would not, meaning that it is in the switch. If I hold the switch on in low or high pushing in on it the motor works so does this mean my switch is bad ? Thanks for any help on this.