Sounds like you have a couple of different issues going on. My understanding is the lights are not working on your cluster and clock. Have you checked the bulbs, not loose or corroded or even burned out? Do you leave the switch on only for 5 seconds? like others, do not turn it on,see what happens, take jumper cables with you, just in case.

I have a switch i have to turn on, then turn the key otherwise the car won't start. If i forget to turn the switch off, after hours it will drain the battery. I changed the toggle switch to an OEM volvo switch and placed it on console with the other switches.
Good luck, post back please.
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Sandy '83 244 dl daily driver

The alternator was acting up? Was it tested? New voltage stabaliser or brushes installed? Maybe your car had battery drain issue they couldn't find in which case I would check the wires to the central door function in the drivers door. Then check for a drain coming from the delayed off funtion of the overhead interior light.Also poorly grounded alternator. That's all I got, you need to wire it back to OE tehn go from there. Who did this fix?

What happens if you don't turn on the switch?
I would investigate the lighting first.
Do get the factory green manuals at k-jet.org. Download the entire set for your model and year. Their free.

This doesn't make any sense to me.

You'll have to investigate the wiring and see what exactly goes where. Grab a Bentley manual, or Volvo Greenbooks, or search here and on Google for wiring diagrams, and undo whatever was done, one wire at a time.