Stumped During cold weather the past three winters, I have experienced the # 2 fuse blowing it was intermittent until now. The truck currently blows a fuse every time i hit the brake. I have taken truck in twice to local dealer to no avail. I have replaced the brake relay switch (ford unit), all the bulbs, adjusted the steering column to different positions, adjusted pedals to different positions, cleaned and inspected all trailer wiring and wiring harness along frame. I need help on whether i have skipped something. Any advise would be welcomed. Everything works fine until you hit brake pedal
03 Expy Blowing taillight and brake fuse
- Thread starter Scott2003
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stamp11127
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You most likely have a short to ground. Fuse pops when you hit the brake since there isn't any resistance on the circuit. Standard electrical troubleshooting applies here. I normally start by isolating the different parts of the circuit then probing each segment for a hot wire that is grounded. Or if is going to be a hassle, I segment a section then probe it, segment another and probe until I've located the shorted section.
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Thermo
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Scott, I will tell you to KISS (Keep it simple). Start off by removing both tail lights and unplugging them. Now, remove the 3rd brake light. With all of these disconnected, do a really good look at the plugs to make sure the pins look silver in color and the plastic is not melted.
Next, under the driver's side rear corner, follow the trailer plug harness back to the plug there. Disconnect that plug.
For this next check, you can use any size fuse as long as it is less than the factory one current wise. Install a new fuse and step on the brakes. Did the fuse blow? If yes, then your problem lies in the wiring harness of the truck and this is going to take some hand over hand inspection. I would first start with the steering column, especially if you like to raise and lower it as you get in and out of the truck. This is also a common fault location as the wiring will rub and get the insulation rubbed off, leading to what you are seeing.
If the fuse did not blow, you have a problem with one of your components in the rear. Remove the fuse and put the factory sized fuse in. Connect up the 3rd brake light. Step on the brake and see if the fuse blows. If yes, you have a problem with the 3rd brake light (disconnect the 3rd brake light and find a replacement).
Now, connect the driver's side tail light. Step on the brake. Did the fuse blow? If yes, your problem lies in the driver's side tail light. Do some looking, could be something simple, could be you need a new tail light. It is possible that a bulb is not seated fully and is causing you problems.
Next connect up the passenger side tail light. Step on the brake. Did the fuse blow? If yes, same situation as the driver's side.
If you have reconnected everything and the fuse still has not blown, then odds are your problem lies in the pigtail for your trailer harness. Get a new harness.
Hope this helps.
Next, under the driver's side rear corner, follow the trailer plug harness back to the plug there. Disconnect that plug.
For this next check, you can use any size fuse as long as it is less than the factory one current wise. Install a new fuse and step on the brakes. Did the fuse blow? If yes, then your problem lies in the wiring harness of the truck and this is going to take some hand over hand inspection. I would first start with the steering column, especially if you like to raise and lower it as you get in and out of the truck. This is also a common fault location as the wiring will rub and get the insulation rubbed off, leading to what you are seeing.
If the fuse did not blow, you have a problem with one of your components in the rear. Remove the fuse and put the factory sized fuse in. Connect up the 3rd brake light. Step on the brake and see if the fuse blows. If yes, you have a problem with the 3rd brake light (disconnect the 3rd brake light and find a replacement).
Now, connect the driver's side tail light. Step on the brake. Did the fuse blow? If yes, your problem lies in the driver's side tail light. Do some looking, could be something simple, could be you need a new tail light. It is possible that a bulb is not seated fully and is causing you problems.
Next connect up the passenger side tail light. Step on the brake. Did the fuse blow? If yes, same situation as the driver's side.
If you have reconnected everything and the fuse still has not blown, then odds are your problem lies in the pigtail for your trailer harness. Get a new harness.
Hope this helps.
Fuse Blew
Thanks everyone for the advice, I disconnected all of the harnesses under the drivers seat. I put in a new fuse and it blew. What would be my next steps I truly believe it is in the front now either in the steering column , adjustable pedals or the brake switch relay wiring This is new territory for me
Thanks everyone for the advice, I disconnected all of the harnesses under the drivers seat. I put in a new fuse and it blew. What would be my next steps I truly believe it is in the front now either in the steering column , adjustable pedals or the brake switch relay wiring This is new territory for me
stamp11127
Full Access Members
They have the brake circuit tied into other circuits, so it isn't an isolated easy to troubleshoot one. Two ways to go about it. The most logical way is to get the wiring manual from Ford and trace the wires. You can usually grab one on ebay. The other is to start following the wires from the brake switch and disconnecting the connectors as you go while testing for a short.
In tracing shorts I use a type 1 circuit breaker so that I avoid spending a small fortune on fuses.
The wiring on my 99 branches into at least three other circuits. One of which feeds the multi function switch. If your lucky the problem will be there. Most shorts occur in bends, pinched areas, wires that contact metal due to worn insulation or sharp edges.
Let us know how it goes....
In tracing shorts I use a type 1 circuit breaker so that I avoid spending a small fortune on fuses.
The wiring on my 99 branches into at least three other circuits. One of which feeds the multi function switch. If your lucky the problem will be there. Most shorts occur in bends, pinched areas, wires that contact metal due to worn insulation or sharp edges.
Let us know how it goes....
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