I have asked the same question in the electrical forum with no reasonable solution. I have also checked back and others are having the same problem but no solution. Already changed headlight switch and relay under the hood with the no change to my problem. The problem; when I pull out the HD switch to the third and last position the headlights come on but no running lights. When I pull the switch to the second position no running lights. But if I pull it a hair more the running lights come on but no headlights and I do hear a relay clicking once which I have replace. It cost more than the HD switch from Ford. If I pull the switch all the way out and then push it in a hair the headlights and running lights work. Like I said I changed the switch already and I can get them to work but it's a pain in the *** getting out of my truck to see if both are working.
Any ideas and it seems others are having this same problem with 80's model Ford Trucks? Thanks for any help! Rich

 

What does the wiring harness look like that attaches to the switch? Maybe you're putting pressure in a certain direction on the wires when you push/pull? I just found some wires in my truck that had gotten really hot at the ends where they attach to the switch because of corrosion...

 

All my wires look fine at the pigtail and are not getting hot. I have followed them through the firewall and again no missing insulation or bare wire. I can usually figure electrical out but this one has me baffled.
Rich

 

For the harness to light switch plug, what happens if you jumper the power wire (heavier) to the wire going out to the parking lights and/or head lights? If that works consistently, it must be a bad new switch, but odd that it would do the exact same thing...

I don't know what color wires to cross, but could look them up if you like. The Haynes manual has a very good schematic diagram.

 

If you could scan that page and upload it here, would be great! I have heard from another post in Misc. Electrical that one of the guys had the same problem with his switch. Here's his solution

OK I have made progress on this problem.

The tan and white wire that was melted in the wiring harness was the culprit. This wire connects to pin B2 on the headlight switch and supplies power to all the park lamps and interior dash lights from fuse #4.(15 Amp) I bypassed this wire by connecting directly from the fuse box to the back of the headlight switch(B2). The lights now work properly. I have not pulled the old wire out to see the problem but it must be a very high resistance connection or broken all together. Very odd that the lights worked with the switch halfway. This must have allowed power to flow from the headlight circuit.
The B2 pin is labeled inside the headlight switch. Just look for the tan and white wire. I'm not sure if this wire has a fusible link powering other circuits but base on what I see in the Haynes schematic it does not.

Hope this solves your problem also EvoDawg.

Going to look into it this week.
Thanks

 

I found the problem it was the tan and white wire (hot) from fuse box into the switch causing the problem. It was frayed and wasnt making good contact. Once isolated and fixed the problem has gone away. Now the switch is working right and all lights are working.
Rich