How do I know if I should buy a new window motor, window regulator, or window switch ?

My 350Z was one of the first built, #254, and I have 97K miles on it. The driver side window has had some occasional problems where it would not go up, but a second try and it would always go up. A couple of months ago it started not going down. It would not go down for a day or two and then start working again. Finally it got really bad. I took the motor apart, emptied a whole lot of black dust, cleaned the motor and it worked again every time. That was for about a month. Now it's not working again, it won't go down many days, mostly mornings.

I was going to buy a new motor, but I see there is a regulator and a switch. How can I tell if maybe the switch is going bad or the motor ?


BTW, my passenger side window had the go up and come down problem and I've reset that motor twice to get it to keep working.

 

"Bang" on the inside door trim with your fist. Early stages of fail will allow temp fix. Just like any rotating elect (starter ect) a sharp thump sometimes works. You need a motor.