Headlight switch on 79 chevy c10 - 1984 Chevrolet C1500

See if the diagrams in the link help

https://www.gmsquarebody.com/threads/85-c10-vacuum-hose-diagram-pics.29486/

https://www.google.com/search?q=1984+Chevy+C10+vacuum+hose+diagram

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Remove the blower motor. Use jumper wires from battery for voltage and ground, it will only run on high speed with the jumpers. Doing it this way, your bypassing some of that other stuff. You could use inline fuse on one of the jumpers or if the wire starts getting hot in your hand, remove it.
Just a thought. Maybe you've already tried it?

Make sure the dimmer portion is not turned to the low/off position on the headlight switch. This will turn off/fade the dash lights

sounds like a multiplug is loose ?but where it is ¿ follow the loom from the back lights backwards

You cannot do this or fit the LED as this will contravening the certificate of homoglonation which will leave you at the mercy of every vigilant police officer whos looking for a contribution to the christmas turkey fund ,thats without the vehicle failing its strict europeon annual vehicle mechanical inspection ,6 months on a commercial vehicle or a taxi

Did you check the starter and starter relay. If the starter is failing it will require more voltage than usual to turn over and start the truck. Heat soaking can also be a problem. Check the wiring to the starter and any wiring you reconnected when you replaced the alternator.

Either this brake has been dragging, or if it's like my 79 c10, It is the only brake working! First, find a good drum new or used to replace the bad one. Next replace all four wheel cylinders, the brake fluid and any pads or parts that are rusted or wore. Make sure the brakes are bled and then be careful not to hit the steering wheel when you stomp the brakes!!!

fuse maybe.....or headlight switch

sounds like a head light switch,,,

There is no fuse for the headlights. There is a circuit breaker in the headlight switch and a fusible link down at the starter. If everything works then I would replace the headlight switch because the fusible link controls all power to the truck except the starter. Hope this helps.