I have an issue with my driverside power window. when i try to open the driver side window with the switch, the motor clicks and hums but does not open the window. I have ruled out the switch by trying another switch. At times, the window works perfectly and then does not function for long periods of time. All the other windows function as does the master switch which will do all the windows. Any thoughts on this would be appreciated. I am thinking it may be the relay but do not know where it is.