i have an 86 240 with power windows and power locks. the previous owner installed an over-ride switch that, when engaged, allows me to operate the power windows with out the key in the ignition. since i have owned it, i have never been able to use the driver switch to put the rear windows up, but i can if i reach back and use those switches. today, i rolled all four windows down and was only able to get the front passenger up, by using its own switch. the driver switch doesn't work at all, and the rears don't work either. i was told it could be dirty switches, but i'm not sure. does anyone have any suggestions?