In general, window switches switch polarity to power the motor in cw or ccw rotation. Unless you're able to disassemble switches to examine them for wear, you're left with making a temporary bypass to wiring to see if up works in each window or replacing the switches. Disassembly can be tricky as springs and parts can fall out without some idea of how they work. Used switches from junk yards may provide either a working switch or a part to disassemble to explore what fails. If you're lucky, dielectric grease used to reduce arc wear of contacts may have hardened, preventing electrical connections. Scraping off dried grease may restore a well worn switch back to full function. Applying new grease helps lube moving parts.