I have an 84 F150 4sp O/d 4x4 that was having some lighting issues. I replaced the headlight switch and stomp switch and now I only have head lights and brake lights but no running lights at all. Any thoughts on what I did? The running lights worked before but the head lights did not. I have wiring diagrams, but I'm not really sure where to start. Fuses are all good in the box. Thanks!

 

My guess is that your original problem wasn't the switch, but the wiring at the switch. I say that because these trucks are well known for overheating the headlight wire right at the switch, causing the insulation on that wire and adjacent wires to fail. So I'm guessing that replacing the switch caused one or more wires to fail.

I would remove the switch from the dash, leaving the wiring attached, and inspect the wires closely.

 

I think the Pico 5730 8 lead pigtail is correct for this application.

It is shown as fitting 1980-1994, but I know that trucks started using 5311 in 1987.

 

So how do I get the dash apart to get to the switch and wires? I snaked my hand up there last time, wasn't fun. Is there an easier way? I think at this point I will just replace the pigtail. The pico is actually a 9 terminal, I already picked it up. Thanks!

 

Oh, the 9 terminal is the Pico 5311 connector.
I thought that was '86-'97 only.

You can push the button on the back of the switch and pull the **** and shaft out.
Then undo the retaining nut.

 

Taking the dash pad off makes things LOTS easier to get at. Might remove the gauge cluster, too.

 

Take the battery cable off.

Pull the headlight switch **** all the way out.

Reach up behind the dash and feel around on the switch on the side that doesn't have any wires. You will feel a little button sticking down. Push in on the button, and pull the **** and the shaft out of the switch.

Then find something to get the nut loose on the front of the switch. Snap ring pliers, little screwdrivers, whatever. They make a special tool but I have never owned one.

The tan/white wire going to the switch is the one that feeds the running lights, and is usually burnt off at the switch.

 

Sooo.. Took me a while to get things ripped apart, etc.. The tan/white wire has power to the switch, fuse is good. Wiring behind the fuse block looks pathetic but it is still supplying power. The switch wiring is all working correctly, pull in/out the correct wires light up however I still have no running lights… Not sure where to look next. The brown wire is getting power to the switch and coming out, my diagram says that wire supplies power to my front running lights. Wrong diagram? Very confused at this point. Thanks!!

 

The brown wire feeds ALL the running lights, front to rear. See if you can find the brown wire under the hood, and see if it has power there.

 

I tracked the brown wire to the first parking light, discovered it has power but is only getting around 8volts. After fiddling, I found that I now have front running lights but they are very dim, and no rear running lights. At the switch, I have normal voltage coming out of all wires except my instruments and running light wires, why would that be? I also popped the fuse a few times during my testing, it was a 10A, I bumped it up to a 15A. Should be ok, right? Why would my voltage be low, or no existent? Thanks again!

 

Anybody? Thanks guys, I do appreciate it!

 

Is the plug at the switch all oxidized on the contacts?
You say the brown wire is getting power, is it getting a full 12.5V?
You may have corrosion at the grounds of the light sockets or the switch contacts can't pass enough power to make the lights work. (even though they work the meter)

Try R&Ring the bulbs looking for corrosion and trace the socket grounds to make sure they are clean and tight where they attach to the body.

 

If I am reading correctly, you now have dim lights, and the low voltage goes all the way back to the switch correct? Do you get low voltage on the tan/white wire? The tan/white is that circuit coming into the headlight switch, and the brown wire is that circuit leaving the switch.

Make sure during all your voltage tests, you poke the wires or probe the plug WITH THE PLUG STILL CONNECTED and the switch in the on position. You need the complete load of all the lights on the brown wire on this circuit when you are testing with your meter. Unplug the plug and test it, and you will probably get 12v. Plug it in and when you get 8v, you need to work your way up the line till you find the problem while the circuit is live and in failure mode.

 

So I found that the tan/white wire was fried at the fuse box, I rewired it from the box to the switch with a heavier wire. I put a 15a fuse in, popped the fuse instantly. I put a 20a in and the lights worked at 9.5v for about 15seconds then the fuse blew. The voltage was correct everywhere until the fuse blew, except for the 9.5v after i turned the lights on for running lights only. What would cause this? Thanks!!

 

It has a short elsewhere.