Auto repair manual for your car with electrical diagrams in it available at most auto parts outlets.
Haynes
where can i find a schematic for a 700 polaris atv
You can go to your local dealer, they will print out the schematic for you.
eBay and Craigslist
You can find a 3-way switch wiring schematic by searching online or referring to electrical wiring books or guides. These resources provide detailed diagrams and instructions to help you with your electrical project.
probably the dalership....or at sears or lowes
Where can I find diagram of electrical system on 1992 cutllas supreme
Your best bet would be to buy a Chilton's repair Manual.
You can find a 4-way switch wiring schematic by searching online or consulting an electrical wiring guide. This will help you understand the proper connections and installation steps for adding a 4-way switch to your electrical circuit.
i think the catalog is called "HAYNES"
When they get their web site fixed, you can see one at AUTOZONE.COM
In a motor manual.