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no rear tun signals/brake lights 78 f100

  #1  
Old 10-14-2018, 01:08 AM
travo
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Question no rear tun signals/brake lights 78 f100

1978 F100 custom 4x4 400M Granny Low
bulbs-check
sockets-check
fuses-check

front signals work like they should as well as all the running lights front and back. no brake lights or turn signals in the back. took the wires off the brake light switch at the pedal. no power. any helpful, but not too technical, information would be greatly appreciated.
 
  #2  
Old 10-14-2018, 06:26 AM
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The brake light power simply runs from the fuse box to the pedal switch, and then up the steering column to the turnsignal switch. I would work on the brake lights first.

Here is a link with a diagram of the fuse box in your truck. It says "f8" is the fuse for your stoplamps and emergency flashers. I would check for power at this fuse.
http://www.fordification.net/tech/im...ster_2of10.png

Here's another diagram link, it's a 1979 but looks the same as yours. In this diagram look at the top and follow line "383 R_W" across from left to right, this is the red/white wire that comes from the fuse box. If you keep following it, it drops down in the diagram and hits the emergency flasher. I do not know where this is located on your truck, maybe you do but it would be a good spot to check for voltage if your fuse box checks out ok. From the emergency flasher it keeps going back up and to the left as a solid red wire. It then goes to the left and there are two ways it can be wired, the lower one is if you have or had cruise control, and it would have a extra switch. If you do not or never had cruise, you follow the top line over, you have just one switch. If you had cruise, there is a plug in shown in the wiring near the switches, make sure it's plugged in.

diagram link of the switch wiring
http://www.fordification.net/tech/im...aster_5of9.jpg
 
  #3  
Old 10-21-2018, 02:39 AM
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Originally Posted by Franklin2 View Post
The brake light power simply runs from the fuse box to the pedal switch, and then up the steering column to the turnsignal switch. I would work on the brake lights first.

Here is a link with a diagram of the fuse box in your truck. It says "f8" is the fuse for your stoplamps and emergency flashers. I would check for power at this fuse.
http://www.fordification.net/tech/im...ster_2of10.png

Here's another diagram link, it's a 1979 but looks the same as yours. In this diagram look at the top and follow line "383 R_W" across from left to right, this is the red/white wire that comes from the fuse box. If you keep following it, it drops down in the diagram and hits the emergency flasher. I do not know where this is located on your truck, maybe you do but it would be a good spot to check for voltage if your fuse box checks out ok. From the emergency flasher it keeps going back up and to the left as a solid red wire. It then goes to the left and there are two ways it can be wired, the lower one is if you have or had cruise control, and it would have a extra switch. If you do not or never had cruise, you follow the top line over, you have just one switch. If you had cruise, there is a plug in shown in the wiring near the switches, make sure it's plugged in.

diagram link of the switch wiring
http://www.fordification.net/tech/im...aster_5of9.jpg
Thank you. I still have a problem somewhere. If the power goes from fuse panel. I am not getting any power at the brake light switch, yet the front signals work. Is it for the rear signals only? Could it be the flasher relay?
 
  #4  
Old 10-21-2018, 02:05 PM
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Forget the signals for now, they are a separate circuit on a separate fuse. Concentrate on the brake light circuit.
 


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