2001 s10 headlights will not come on all the time

Replace the switch. The low beam side of the switch isn't making a connection.

I would check for voltage at the headlight switch. Also look for a headlight relay in the box in the engine compartment.

Check to see if you have power to the "ILLUM" fuse in the instrument pane fuse block (drivers end of the dash). there should be power with the headlight switch in the park or headlight position. If there is no power than make sure the dimmer control is not turned off on the headlight sitch. If is is not off than sheck for power on the dark green wire on the connector for the headlight switch. If there is no power an there is power on the orange wire than unplug the connector and jump those tow wires. If the dash lights come on replace the headlamp switch.

Let me know if you have any questions and I'll be happy to help.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

THE HEADLIGHTS DO WORK ON A DIFFERENT WIRE AT THE SWITCH, ALSO THERE IS A RELAY FOR THE HEADLIGHTS USUALLY LOCATED IN THE MAIN FUSE BOX UNDER THE HOOD. CHECK THE RELAY FIRST, THEN YOU MAY WANT TO GET A WIRING DIAGRAM OR CHILTON MANUAL TO CHECK THE WIRES COMING OUT OF THE SWITCH.

I had a similar problem on my 2001 Caravan. Turned out to be a loose connection between the frame control module and the fuse box. I unscrewed the frame/front control module from the fuse box and bent the tabs slightly to make better contact. Then tighten down the module securley. Need star driver to loosen screws

The relay has nothing to do with the tail lights, but replacing the switch sounds like a good idea. There's a nut holding it in place, see http://www.skandix.de/en/spare-parts/electrics/switches/switch-headlight/1027524/ to get an idea of the construction. And the price. This is not worth fiddling about unreliable workarounds...
In addition, if fuses 15 and/or 16 burn frequently there might be a problem with the tail light cabling.

Good luck
Ingo

does the instrument panel lights come on when you turn on the park lights only (no headlights)? If not it could be the switch itself.

I had an S-70 with the same problem what happens is the headlight switch tabs that hol it together broke and the switch was slightly separated and connection was not there for the headlights and also check the high beam see if headlights come on i dont think it is a relay or fuse??? proballally the headlight switch and easy to replace you even can use one from an 850 model

the head light switch

I am not much of a mechanic any more ,but I do have some experince with electronics and for any circuit to operate battery has to flow to ground.Direct battery to ground will blow a fuse or melt your wiring if the fuse does not blow.If your parking lights stay on all the time then there is a complete path from battery to grd through the lights,and it sounds as though what ever is causing the problem on the parking lights is killing the path to your lamps relay.A wiring diagram may be available on the internt or library.Good luck.

tk46