back-up lamp switch

Hello all.
Can anyone tell me the location of the back-up lamp switch on a '67 Chevy Sportvan? Reverse lights are out and the bulbs are fine.
How can i proof that the switch is fine?
Thanks

Here is a link to some 2nd Gen Wiring diagrams https://vintage-vans.forumotion.com/t25631-second-gen-wiring-diagram

If you would like to see some other info, you can use the search tab at the top of the page and search on backup... Hope this helps.

Is the fuse good,,,,,,,,,is it a manual transmission with this switch connected to the trans linkage?

Thank you very much to vanny!

@donivan65, the fuse is ok. It's a power glide transmission. There is a switch with four wires. I don't know, how I can test it.
Other question, is the wire for the back-up light connected with the steering column?

That 4 wire switch is the safety neutral and back up light switch on our primitive vans,,,,,unless some has,,,,,,,,,improvised,,,,,,over the past 50 years, purple wires are for the starter,,,,one gets its juice from the ignition switch when you turn key to START,  if the switch sees that the trans is in Park or Neutral, it sends juice to the starter solenoid to crank the engine,,,,,,then the Light Green wires work the same way,,,,one has juice from the fuse and if the switch sees that the trans is in Reverse it sends that juice to the back up lights,,,,but it probably has to go through the connector behind the left rear tail light to get to the back up light wires,,,,,,so get a 12 volt test light or volt meter,,,,see if you get voltage with the key on at one of those light green wires at the switch connector,,,,if you do, jump the 2 light green wires together, that should turn on the back up lights,,,,,see what you find, then we can talk more,,,,,,also,,,is that switch hooked up with a little rod connected to the shift rod? does that van start in Drive or Low?

Don you need too put the knowledge you have on our vans on video or paperback so we will always have it with pictures of course