This is for a '99 Expedition, but I thought I'd post this here to tap into all you F150 gurus.

The brake lights are not functioning. Here's what I've done:

1. All known related fuses have been checked and appear to be intact.
2. Third brake light over the rear gate does not function, either.
3. Brake light bulb filaments appear to be intact.
4. Brake (BOO) switch was replaced, but problem was not corrected.
5. All other functions on multi-function switch (blinkers, wipers, high beams, windshield wipers) work properly.
6. Tilt steering wheel was raised and lowered, and multi-function switch functions were conducted WHILE brake pedal was depressed, but brake lights did NOT come on.

I'm guessing it could be a wire that has shorted out. It's also possible that I haven't checked the correct fuse or relay. For the latter, does anyone know the actual descriptor of the fuse that controls power flowing to the brake lights?

Other suggestions before I throw in the towel and take it to a garage?

Thanks!

 

Check Fuse F13 in the under-dash fuse box.

If good, check for power at the LG/RD wire at the brake pedal switch.

If good, check for power at the LG wire at the brake pedal switch.

The LG wire goes to the 3rd stop lamp, the trailer tow relay, and to the multi-function switch.

 

First, thanks goes out to those who responded with suggestions to my initial posting regarding the brake light failure.

After trying some of them, I learned someone from my church runs an automotive electric shop, and I later took it there. I told one of the technicians all the trouble shooting steps I had taken (some of which were suggested by FTE members), and he replied all of those steps were exactly what they would have done, too.

It turns out a wire leading to the Brake (BOO) switch had burned out. This wire provides power to the brake lights, and goes through the BOO switch and up to the switches on the steering column before going out to the brake lights themselves. (Someone suggested I use a voltmeter to test the power to the BOO switch, and this would have narrowed the search. But since I'm challenged by replacing the batteries in a flashlight, this step was beyond my skill. When one starts saying exotic words like "volts, amperes, ohms" and the like, you might as well be speaking Yiddish to me.)

I occasionally pull a U-Haul or boat trailer, and the added power demands placed a strain on this wire, leading it to fry. I had pulled a boat several days ago, and it may have led to the light failure. This is troubling to me, since I was under the impression that this vehicle was designed from the ground up to pull trailers. It even had the "Towing Package" as one of its options. The gentleman at the repair shop said this would have never happened 20 or 30 years ago, because things like this wiring were much more robust then. He also assured me it will happen again if I pull enough trailers. Great.

At least there's some consolation that it took 12 years for the wire to burn through. If it takes that long to occur again, well, the vehicle would be an antique and would receive my compassion due to its senior citizen status.

At any rate, the brake lights are working once again, and I'm looking forward to getting back to the lake and burning out that wire again.

Thanks again, everyone.

 

Nope.

There should be no extra load on that wire when using a trailer harness since all the power for the trailer goes through separate relays. The current draw through the brake switch and its wires is the same regardless of whether there is a trailer attached or not, assuming a standard setup (not a hack job)

That wire does get flexed which is what leads to its not so very uncommon failure.

 

Hate to drag up such an old post... but this has been the closest to my own situation.

What wire caused the issue? Where is it located? colors?

2001 F150 SC. Intermittent brake lights.
If the truck sits over night & is cold the lights work. By the time we get into town 15min there is no lights. Im thinking now with winter here & the heater on blowing hot air under dash there is a fuseable wire getting hot & not working.

Any other suggestions on what to test or look for would be great.

 

No problem bring up old posts with good qualifications and purpose. Unfortunately, the original poster hasn't visted the site in a year and ahalf, so there's no way of knowing what happened with his truck....

The circuit isn't very complicated, but we do need to narrow it down, a task my questions are intended to do. Need to focus a bit first.

First off, are all three brake lamps affected or is in only the corners.

Are the turn signals (Key on - cold) or the hazards (Key off -cold) affected at all? How about after full warm-up?

Check the female contacts for fuse f13 for excessive looseness. Wire colors in post # 2 are applicable to your '01.

Quite possibly, it's thermal expansion and contraction that is causing an otherwise broken connection to make or break. Might be other things, too early to tell without more information

Make the requested observations and we'll get you squared away.

 

Thanks project...

Went back outside this morning after posting. Turns out it is in the Steering colum.

I went out & stepped on the brake pedal, door open & one foot in the truck on pedal. Brake lights come on.
Reached in & moved the tilt down 1 notch, brake lights go out. Moved back up lights on. Tried all tilt postions & turning wheel no lights.

Which wires am I looking for LG/RD from the BOO switch up the steering colum? Or another combination?
Its -20 out today & no heated shop so this might be a spring fix & just have to drive with the steering wheel in full up postion.

 

In that case, you probably still have the high-mount stop lamp that's working, even when the corner stop lamps aren't. Please verify.

If the HMSL is still working, then most likely you have the common problem where the wiring harness up the column is too tight and you've got a wire that's pulling on the pin and making it intermittent.

The most common point of failure will be either where the brake lamp signal goes into the multi-function switch (LG wire, connector C258) or lower down the column where there's a connector that comes from under the dash and goes up the column (also LG wire, connector C253). I know there are threads with photos of this problem somewhere on the forum, but I don't have a specific thread to point you towards.

 

Project.... yes the HMSL is working. Wasnt at first but gave it a tap with the snowbush & it came on. So loose or corroded connection there.
Once the HMSL was working no other brake lights on. Daughter had foot on brake & tilted the steering wheel through all postions. Brake ligths work with tilt in full up postion, no other.

So for now that is how she will have to drive it. Will look into pull plastic panels if I can get it over to a firends shop with heat for ahile.

 

Let us know what you find. If you can snap a photo of the culprit, please do so.

Nasty temps up there! We're unseasonably warm here in St Louis. Would you believe shorts and t-shirts weather (mid 70s) on the first weekend of December?

 

Good thing I enjoy the winters. But after 20yrs up here I guess I better.
I thought the east was getting cooler temps aswell but enjoy it while you can.

How much of a pain is it to get to the multi function wire harness?

 

You have to take the column shrouds off.

Set e-brake and place shifter in neutral
Disconnect battery
Remove ignition cylinder (most models)
Lower column all the way, then remove tilt lever
Remove screws from bottom and remove lower half of shroud
Move shift lever to manual 1st, then remove upper shroud

 

thanks for the write up. not to much but not going to try it in this weather.