Electric window problem

[Uruk Hai]

My car has electric windows (VW kit but not factory fitted) and lately the passenger side one has started working when it feels like it, I've tested the lives on the switch and its fine, both up and down. Then I took the door panel off and tested the wires at a connection plug about 4 inches from the motor and again both up and down were fine and now the window is working O.K. ? I know this is a bit of an open question but does anyone have any suggestions as to what could be the cause of this, the other thing is when I wind the window up the motor seems to labour a bit, can anyone tell me which bits to lubricate and what with ? Any help appreciated as my door is still in bits 

[clipperjay]

Mine completely stopped working once when I jacked up the car the plug located at the bottom came lose so I just got some sand paper and tried to scrap the oxidisation or blue stuff of the dirty connectors and hey presto!. Water can affect the plugs if water gets into the plugs. Or it could just be your solenoid is on its way out?

[Uruk Hai]

Its working fine at the moment and when I pulled the switch out to have a look at it I made sure all the spade end connections were pushed all the way onto the back of the switch before testing so I'm wondering if it was as simple as a spade end comeing loose over time ?

[monkeyalan]

I spray silicone down the runners every couple of months just to ease friction.