No brake lights! Very frustrating.
We have a 2007 Ford E450 chassis motorhome. For some dang reason the brake lights are not working. The fuse (#11) is good AND the hazards are working properly. The running lights are working...
Forum Discussion
Okay - here's what we found.
I FINALLY found a wiring diagram that told me what the wire color is from the tail-light harness to the firewall connector. It is heavy-gauge wire, Light Green/Orange in color. The wire from the brake fuse circuit, 511 / fuse #39 is a thin-gauge light green wire.
I had originally thought the tail-light wire ran down the footwell and then down the rail to the harness connectors over the axle - because so many fuse-panel wires are routed this way. My inability to identify that wire really made this job difficult, if not utterly impossible. Well, MANY fuse-panel wires run down the footwell, MANY do not. I know that now.
It turns out the wire runs all the way along the frame from the harness over the axle, moving forward past almost to the firewall where it terminates in a giant harness connector that is actually bolted together!! Then, the whole shebang continues up the engine firewall behind the coolant reservoir.
I visually traced the heavy wire all the way from the chassis connector, moving forward. It was very, very well-wrapped and loomed pretty much the whole way. Once the bundle gets near the engine, the wrapping becomes even more significant - protecting the wires from engine and exhaust heat.
I couldn't assume that the run along the frame was good but my hunch was that it was okay simply because I didn't see any place where potential damage could happen.
That left the bundle from the frame connector to the firewall.
I have no way of knowing whether or not this bundle had ever been wrapped but I can say that this was, in it's current state, largely unwrapped. It seems like a pretty important bundle of wires in a vulnerable place to be left uncovered like that.
I moved the coolant reservoir out of the way to give me a better look at the exposed mass of wires (when did cars get so **** complicated???). The bundle was dirty but tight. Except for two wires which seem to have been torn, as if something had snagged them. The wires were sticking out of the bundle awkwardly.
One is yellow and blue. One of them is light green. LIGHT GREEN.
I put a test light on the upper stump of wire and shorted the brake switch.
Bingo. It lit.
At this point I couldn't be totally sure that the wire was accidentally cut or intentionally cut (for some reason) so I connected the broken wires together with a 7.5 amp fused connector I made from some wire bits. Just to be safe. Then I jumped the brake light. I heard the relay close.
Brake lights. BRAKE LIGHTS. !!!!BRAKE LIGHTS!!!
At this point I can only assume that somehow I've NEVER EVER had brake lights. Maybe.
My wife followed me in traffic a few months ago and she said she could "barely" see my brake lights. Maybe she was just seeing things. Now they're super-bright.
I can't say for sure what my situation was before I repaired the broken wire since I have never checked by brake lights before. I can't say for sure that the wire I repaired was, previously, the sole provider of current to my brake lights. I have no way of knowing. The diagram shows several wires coming off F39/circuit 511 and I did find three of those wires when it was all said and done.
In the diagram I posted earlier you can see what is basically a ground coming right off #39. It is throttled by a 180-ohm 6.5-watt resistor. I think this might be here to keep the circuit active even if all bulbs burn out (or are removed) so that some of the PCM/Brake functions will still work. The brake signal might change the engine functions - it most likely tells the transmission to downshift when you are in tow/haul mode.
I'm only guessing.
The main thing I've learned from this fiasco is that I really, really need access to better documentation. I also need to educate myself a LOT more about reading circuits. The good thing is I still value persistence. I spent three whole days on this and I even had the help of some fellow campers and even my camp-host who has a small fix-it service here in Lusk, Wyoming.
And of course I've gotten some very excellent help here on this forum (and others).
Anywhoozle, I can't be sure I've totally, utterly fixed this. Mostly because I am **** surprised that it was something as simple, prosaic and elemental as a broke wire. A. Broken. Wire.
Thanks to everyone on this thread and everyone in Lusk, WY.
(stay tuned. I hope this is my fix. maybe not. old wiring is fickle)
I FINALLY found a wiring diagram that told me what the wire color is from the tail-light harness to the firewall connector. It is heavy-gauge wire, Light Green/Orange in color. The wire from the brake fuse circuit, 511 / fuse #39 is a thin-gauge light green wire.
I had originally thought the tail-light wire ran down the footwell and then down the rail to the harness connectors over the axle - because so many fuse-panel wires are routed this way. My inability to identify that wire really made this job difficult, if not utterly impossible. Well, MANY fuse-panel wires run down the footwell, MANY do not. I know that now.
It turns out the wire runs all the way along the frame from the harness over the axle, moving forward past almost to the firewall where it terminates in a giant harness connector that is actually bolted together!! Then, the whole shebang continues up the engine firewall behind the coolant reservoir.
I visually traced the heavy wire all the way from the chassis connector, moving forward. It was very, very well-wrapped and loomed pretty much the whole way. Once the bundle gets near the engine, the wrapping becomes even more significant - protecting the wires from engine and exhaust heat.
I couldn't assume that the run along the frame was good but my hunch was that it was okay simply because I didn't see any place where potential damage could happen.
That left the bundle from the frame connector to the firewall.
I have no way of knowing whether or not this bundle had ever been wrapped but I can say that this was, in it's current state, largely unwrapped. It seems like a pretty important bundle of wires in a vulnerable place to be left uncovered like that.
I moved the coolant reservoir out of the way to give me a better look at the exposed mass of wires (when did cars get so **** complicated???). The bundle was dirty but tight. Except for two wires which seem to have been torn, as if something had snagged them. The wires were sticking out of the bundle awkwardly.
One is yellow and blue. One of them is light green. LIGHT GREEN.
I put a test light on the upper stump of wire and shorted the brake switch.
Bingo. It lit.
At this point I couldn't be totally sure that the wire was accidentally cut or intentionally cut (for some reason) so I connected the broken wires together with a 7.5 amp fused connector I made from some wire bits. Just to be safe. Then I jumped the brake light. I heard the relay close.
Brake lights. BRAKE LIGHTS. !!!!BRAKE LIGHTS!!!
At this point I can only assume that somehow I've NEVER EVER had brake lights. Maybe.
My wife followed me in traffic a few months ago and she said she could "barely" see my brake lights. Maybe she was just seeing things. Now they're super-bright.
I can't say for sure what my situation was before I repaired the broken wire since I have never checked by brake lights before. I can't say for sure that the wire I repaired was, previously, the sole provider of current to my brake lights. I have no way of knowing. The diagram shows several wires coming off F39/circuit 511 and I did find three of those wires when it was all said and done.
In the diagram I posted earlier you can see what is basically a ground coming right off #39. It is throttled by a 180-ohm 6.5-watt resistor. I think this might be here to keep the circuit active even if all bulbs burn out (or are removed) so that some of the PCM/Brake functions will still work. The brake signal might change the engine functions - it most likely tells the transmission to downshift when you are in tow/haul mode.
I'm only guessing.
The main thing I've learned from this fiasco is that I really, really need access to better documentation. I also need to educate myself a LOT more about reading circuits. The good thing is I still value persistence. I spent three whole days on this and I even had the help of some fellow campers and even my camp-host who has a small fix-it service here in Lusk, Wyoming.
And of course I've gotten some very excellent help here on this forum (and others).
Anywhoozle, I can't be sure I've totally, utterly fixed this. Mostly because I am **** surprised that it was something as simple, prosaic and elemental as a broke wire. A. Broken. Wire.
Thanks to everyone on this thread and everyone in Lusk, WY.
(stay tuned. I hope this is my fix. maybe not. old wiring is fickle)
