Taillights Out

[rpm427]

I've got a 94 F-350 that when you put the headlite switch on I have NO taillights or brake lights etc. and sometimes the ABS light stays lite.Is this a switch problem or headlight switch problem?I also forgot to mention that sometimes the windows don't go up or down until you use a turn signal or something to that effect.Also when you use the cruise and use the turn signal the cruise goes off by itself so what's going on?

 

[franklin2]

If the turnsignals and brakelights work with the headlights off, but don't work with the headlights on, then it's a grounding problem at the lights in the rear. It could be a bad connection from the brass part of the bulb to the little tang in the socket, I have had the sockets go bad internally on this connection also, or the black ground wire leaving the taillight sockets is not properly grounded.

You can test this theory by getting a scrap piece of wire and jamming in down beside the bulb so it touches the brass part of the bulb, and then ground the other end of this wire. If your problem is solved, then you know the ground is the problem.

 

[HuskerCoalRoll]

From the symptoms you are describing it sounds to me like your multifunction switch (The turn signal, high/low beam and wiper switch) is going out. These are fairly easy to replace and ford has been using these switches from the late 80's to now in the super duty's!

 

[flareside_thun]

From the symptoms you are describing it sounds to me like your multifunction switch (The turn signal, high/low beam and wiper switch) is going out. These are fairly easy to replace and ford has been using these switches from the late 80's to now in the super duty's!

x2

 

[rpm427]

I just replaced that switch not too long ago as my emergency fashers didn't work.I've got brake lights and taillights that aren't very bright with headlight switch off and with the switch pulled on NOTHING?I'm thinking the headlight switch is bad as a couple of times I pulled the headlights on and they didn't come on until playing with the switch off/on a couple of times.How do you get the switch out etc. anybody know?Give me some detail instructions?...Tanks

 

[franklin2]

I've got brake lights and taillights that aren't very bright with headlight switch off and with the switch pulled on NOTHING?

The lights are dim because they are using the taillight wiring as a ground, going backwards through the taillight filament and the brown wire. When you turn on the headlights, the voltage coming down from the headlight switch is blocking what little ground they found through the taillight circuit, and they go completely out. Classic case of a bad ground to the rear bulbs.

 

[rpm427]

Pulled the headlight switch out and the connector in the middle had a slight burn place on it from the top row of wiring.The color of the wire is tan with white strip so either the switch is junk which I seen where Ford had recall on a switch this year or it's something else as I checked ground on rear frame and it looks fine as I cleaned it and greased?

 

[Shadetreemechanic]

The lights are dim because they are using the taillight wiring as a ground, going backwards through the taillight filament and the brown wire. When you turn on the headlights, the voltage coming down from the headlight switch is blocking what little ground they found through the taillight circuit, and they go completely out. Classic case of a bad ground to the rear bulbs.

Yep, what he said.

 

[TWeatherford]

Agnem told me that the ABS memory keep alive is connected into the running light circuit on these trucks. I still haven't found it to unplug it to eliminate it from my circuit, to see if its the reason fuse number 4 blows as soon as I turn the lights on. Sounds like you have a little more problems than me, but I've been trying to track it down for months and am very close to just running my own running light circuit off a switch.

 

[franklin2]

Pulled the headlight switch out and the connector in the middle had a slight burn place on it from the top row of wiring.The color of the wire is tan with white strip so either the switch is junk which I seen where Ford had recall on a switch this year or it's something else as I checked ground on rear frame and it looks fine as I cleaned it and greased?

Read my first post in this thread, and do the scrap piece of wire test down beside the bulb. If that fixes the problem, you have a bad ground. If it doesn't you can move on to something else.

 

[rpm427]

Where is this ground that you are talking about as I seen one on rear of frame above hitch and cleaned and greased it and still same problem.I also replaced brake light switch and light switch as the fender lights also quite working and headlight switch fixed that problem but no taillight or brake light with the switch on?Also while working on truck I disconnect battery cable on selnoid and went to replace the cable and starter engaged.Put key in ignition switch and turned off/on and reconnected the cable and it didn't do it again so what is going on?

 

[Shadetreemechanic]

Run a new ground from the bed to the frame. It will take about 10 minutes and either fix the problem or eliminate it from your troubleshooting.

 

[franklin2]

The ground starts at the brass part of the bulb. Your problem could be in the bulb socket, inside the bulb socket plastic housing, the connection of the black wire to the bulb plastic socket, a problem with the black wire somewhere along it's length. It could also be a problem with the bed grounding like was said in the previous post. In the end, the brass part of the bulb needs to be hooked to the battery negative. Lots of areas along the way that could prevent this.

 

[wmoguy]

My 93 did this and it turned out it was the fuse. If you haven't checked there I would do so. Only difference is mine wasn't giving me issues with the windows.

 

[rpm427]

Which fuse was it that gave you problems?..Also I did the wire test deal and on one side of bulb I grounded it and light came on.The ground on back of frame on drivers side has two wires tied in together with a bolt and when I disconnected it the marker lights on fenders went out and redid it they came back on but no talights or brake lights.Are all the tailights etc.tied to that ground or is there another as I asked earlier and where is it?Also why do the brake lights etc.work with switch off and not when you pull headlights on?