No running lights?
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Junior User
Joined: Jan 2006
Posts: 96
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From: West Haven, CT
No running lights?
84' F150, 351W, 4x4. I just replaced the dimmer and headlight switches but now I have no running lights. Headlights work fine but I have no instrument illumination or running lights. My fuse diagram says I am missing a fuse in position 4 but a replacement 15amp fuse does nothing. Any ideas? Maybe my diagram is wrong? I am also missing fuses 2/3 but a normal fuse doesn't fit there. Help! Thanks fellas!
Old School Hot Rodder
Joined: Feb 2006
Posts: 6,472
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From: Exmore, VA
The diagram is correct, fuse #4, 15 amp is the correct fuse for running lights. 2 & 3 are not used. What I can't find is where fuse #4 gets it's power from. I would check to see if you are getting power to the fuse and then see if you have power at the tan with white stripe wire to the headlight switch. From there it comes out as a brown wire to running lamps. Dash lights are fed from the headlight switch through a light blue with red stripe wire and fuse #17.
Headlight switch terminal A is running light power in, R is out, I is dash lights, B is headlamp power in, H is headlamp power out, D1 and D2 are dome light on control. The Ford switches have these molded in if I remember correctly. Unfortunately I don't have a good way to post a picture of the switch plug from where I am right now.
Headlight switch terminal A is running light power in, R is out, I is dash lights, B is headlamp power in, H is headlamp power out, D1 and D2 are dome light on control. The Ford switches have these molded in if I remember correctly. Unfortunately I don't have a good way to post a picture of the switch plug from where I am right now.
Moderator
Joined: Jan 2001
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From: Virginia
Fuse #4 is hot all the time. There are two buss "bars" in the fuse box. One hot all the time that is fed by the yellow wire from the battery, and the other is hot in run buss, which is fed by the ignition switch.
Old School Hot Rodder
Joined: Feb 2006
Posts: 6,472
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From: Exmore, VA
Dave, I'm aware of that, the fact that he has headlights would lead me to believe he should have power at fuse #4. My suspicion is either a connector at the switch is pushed out or he got a bad switch (probably Chinese made).
Moderator
Joined: Jan 2001
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From: Virginia
No, the headlights have their own power supply that comes directly from a fusible link over near the starter solenoid. It's fed by a black/orange wire. The headlight wiring skips the fuse box entirely, and they have their own circuit breaker inside the headlight switch.
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From: Denver Metro Area, CO
The running lamps and dash backlighting are two different circuits.
If they all worked prior to replacing the switches and the only change was replacing the switches and now they don't work, change the switches back and see if they work again.
That would tell you the problem almost necessarily lies in the switches or their connections to them.
IIRC power comes into the headlight switch via the big fusible-linked wire connected to the starter solenoid. The switch has a circuit breaker for the headlamps.
Wires for the other circuits lead from the switch, to the fuse panel, and then to the running & dash lamps (and all the others).
If they all worked prior to replacing the switches and the only change was replacing the switches and now they don't work, change the switches back and see if they work again.
That would tell you the problem almost necessarily lies in the switches or their connections to them.
IIRC power comes into the headlight switch via the big fusible-linked wire connected to the starter solenoid. The switch has a circuit breaker for the headlamps.
Wires for the other circuits lead from the switch, to the fuse panel, and then to the running & dash lamps (and all the others).
Moderator
Joined: Jan 2001
Posts: 57,014
Likes: 2,751
From: Virginia
The running lamps and dash backlighting are two different circuits.
If they all worked prior to replacing the switches and the only change was replacing the switches and now they don't work, change the switches back and see if they work again.
That would tell you the problem almost necessarily lies in the switches or their connections to them.
IIRC power comes into the headlight switch via the big fusible-linked wire connected to the starter solenoid. The switch has a circuit breaker for the headlamps.
Wires for the other circuits lead from the switch, to the fuse panel, and then to the running & dash lamps (and all the others).
If they all worked prior to replacing the switches and the only change was replacing the switches and now they don't work, change the switches back and see if they work again.
That would tell you the problem almost necessarily lies in the switches or their connections to them.
IIRC power comes into the headlight switch via the big fusible-linked wire connected to the starter solenoid. The switch has a circuit breaker for the headlamps.
Wires for the other circuits lead from the switch, to the fuse panel, and then to the running & dash lamps (and all the others).
The fusible link wire feeds the headlights only. Goes into the switch, and then back out to the dimmer/hi-lo switch in the floor. Nothing to do with the running lights or dash lights.
The running lights are fed from the fuse in the fuse box. From the fuse it goes to the headlight switch, to it's own set of contacts in the switch,, and then back out to all the running lights.
The dash lights are fed from the running lights. There is a "splice" or branch inside the headlight switch, and when the running light circuit is activated, power is tapped off the running lights, and is fed through the variable resistor in the front of the switch. It comes out of the resistor and goes back down to the fuse box to the instrument lighting fuse. Then it goes to the cluster lights. That's why if the running lights fuse blows, you lose the instrument/cluster lights also.
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Moderator
Joined: Nov 2007
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From: Denver Metro Area, CO
If I am reading your post above correctly, that's not right either, except for the 1980 models.
The fusible link wire feeds the headlights only. Goes into the switch, and then back out to the dimmer/hi-lo switch in the floor. Nothing to do with the running lights or dash lights.
The running lights are fed from the fuse in the fuse box. From the fuse it goes to the headlight switch, to it's own set of contacts in the switch,, and then back out to all the running lights.
The dash lights are fed from the running lights. There is a "splice" or branch inside the headlight switch, and when the running light circuit is activated, power is tapped off the running lights, and is fed through the variable resistor in the front of the switch. It comes out of the resistor and goes back down to the fuse box to the instrument lighting fuse. Then it goes to the cluster lights. That's why if the running lights fuse blows, you lose the instrument/cluster lights also.
The fusible link wire feeds the headlights only. Goes into the switch, and then back out to the dimmer/hi-lo switch in the floor. Nothing to do with the running lights or dash lights.
The running lights are fed from the fuse in the fuse box. From the fuse it goes to the headlight switch, to it's own set of contacts in the switch,, and then back out to all the running lights.
The dash lights are fed from the running lights. There is a "splice" or branch inside the headlight switch, and when the running light circuit is activated, power is tapped off the running lights, and is fed through the variable resistor in the front of the switch. It comes out of the resistor and goes back down to the fuse box to the instrument lighting fuse. Then it goes to the cluster lights. That's why if the running lights fuse blows, you lose the instrument/cluster lights also.
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Post Fiend
Joined: Jul 2004
Posts: 8,786
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From: Northern California
The late 70's models when it comes to headlamp wiring, and the 1980, are identicle.
The wiring and switch changed in 1981 due to the addition of Halogen headlamps, and those required more power. The 1980 and older wiring couldn't handle the increased power demand of halogens.
From the symptoms I'm seeing.. He either dislodged one of the terminals in the headlamp connector, Got a switch for the wrong year by mistake (1980 or older), got a defective switch, or there is a problem with the wiring or fuse panel.
If it stopped working when the switch was changed, I would do what CTUBUTIS (chris) suggests and swap the old one in momentarily and see if they come back. If so, then it was the switch.
Process of Illumination (elimination) etc...
The wiring and switch changed in 1981 due to the addition of Halogen headlamps, and those required more power. The 1980 and older wiring couldn't handle the increased power demand of halogens.
From the symptoms I'm seeing.. He either dislodged one of the terminals in the headlamp connector, Got a switch for the wrong year by mistake (1980 or older), got a defective switch, or there is a problem with the wiring or fuse panel.
If it stopped working when the switch was changed, I would do what CTUBUTIS (chris) suggests and swap the old one in momentarily and see if they come back. If so, then it was the switch.
Process of Illumination (elimination) etc...
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