My headlights are acting weird..... new switch on floor and dash... new bulbs ..... when I pull switch all the way only the head lights come on, no running lights...... if i push it ţo the running light nothing...... if i play with it in between both come on.... and all this with only the high beams.... low beams turn off all the lights.. help

 

Thinking the switches are good being new, they still could be bad, I would look at grounds and fuses and bulbs.

Pull the fuses to check maybe just replace them.
At the floor switch pull the plug and with a test light and jumper wire put the head lights on. You should have power on 1 of the 3 wires, ! wire is low beam the other high beam.
Take the jumper and go from the power to 1 of the wires and you should have head lights.
Then jump to the other wire and should have head lights again.

Before you jumper the wires did you have running lights?
Did they go out when jumping the wires?
If yes I would say grounds a re bad or missing.

Grounds: you have a cable from battery to motor, motor to frame either a heavy gauge wire from the motor OR frame to the body.
My truck 81 F100 has a heavy wire from the motor to the fire wall to ground the body.

There is also a bunch of wires from the harness to a screw on the fire wall and at each fender at the side marker lights there are grounds.
On some trucks there are grounds at each rear light. My parts truck 81 F100 style side had at each rear light.
Don't know on my flare side as it was a mess of wires out back, stock the lights get ground thru the light brackets to the bed.
If the bed is not grounded to the frame and frame to battery you will have issues with the lights.
Dave - - -

 

This is a very common problem on these trucks. You have several different power feeds to the headlight switch. You have lost the power feed for the running lights. By putting the headlight switch inbetween positions, you are crossing the contacts in the switch and using the headlight power to feed the running lights.

First thing to do is check the fuse. The running lights have a fuse in the fuse box.

If the fuse is good, you most likely have the very common problem of a wire burnt off on the headlight switch plug. The wire would be the tan/white wire that comes from the running light fuse and feeds the switch. If the fuse is good I would pull the headlight switch back out, and look for this wire. It may simply be burnt up and still there, or it may be gone all together it sometimes burns completely off and is hanging around in the wiring. You used to be able to get a new headlight switch connector pigtail from the stores and online.

 

Do you have a wiring diagram for the headlight switch

 

Here is a diagram for a 1986. You can see the T/W (tan/white wire) coming in the top, going through it's own section and then out to the marker lights. You can also see inside the switch where it taps off this circuit and goes to the dimmer and then feeds the cluster lights. The headlight section of the switch is to the left and is not shown in this diagram.