Brake Lights out

johnwartjr

Registered User
95 SC

Both brake lights and the high mount brake light are out. The turn signals, backup lights, and rear lights light up just fine, they just don't get 'brighter' when I get on the brakes, and the high mount never works.

I am trying to determine where to troubleshoot.

The fuse is good, and other accessories such as the 4 way flashers use the same fuse, and they work.

Is there a mechanical switch the brake pedal actuates that could be bad? Or a relay somewhere?

Any ideas? It's cold outside, and I'm hoping someone has seen this before so I don't end up rolling around on the ground trying to find a fault and freezing my behind off!

Thanks!
 
check the brake light switch on the brake pedal it has a yellow button that contacts the pedal make sure when pedal is pressed the button is release that turns the brake light on. Its a start.
 
Obvious first test is the BOO (Brake On/Off) switch. One quick test without laying on the ground - get it up to speed, set the cruise, and then tap the brake pedal. If it drops cruise, the switch is good. If it doesn't, the switch is bad, or the wiring to it. (Same switch, does both lights and "OMG He's braking DUMP THE CRUISE CONTROL!!")

Don't go down very far - there's a vacuum dump up above in case the BOO DOES fail to operate *grins*

Now, if the cruise doesn't drop, I'd do the BOO first.

If it DOES drop, your next most likely failure would be the multi function switch (MFS), that gadget that has the hi/lo beams, the turn signals, and the hazard switching in it in the steering column.

But I'd bet BOO because, at least in the 1991, the high mount brake light doesn't go through the MFS.

RwP
 
Well, an update

Cruise doesn't work at all.

So, I tried to do this test, and it won't work, because cruise won't work.

I have 2 thoughts on this, and wasn't sure which one to chase first

1) Could the BOO switch be shorted closed? Perhaps the cruise won't turn on if it thinks the brakes are applied?

2) Could the multifunction switch be to blame? I know the cruise controls are on the steering wheel, but I recall in previous vehicles that the cruise controls were on the stalk.

How hard is it to get the BOO switch out to have a look? Does the entire brake pedal assembly have to come out?

On the bright side, I found 6 bucks under the drivers seat while I was rooting around earlier :)

Thanks!
 
Also, I'm confused as to the function of the shift interlock. With the car running, in park, I can shift it into gear without pressing on the brake pedal. Is this behavior correct? I thought I had to have it in park to shift gears.

Starting to wonder if all 3 of these issues are tied together.

How does anyone get to this dang switch, short of being a double-jointed contortionist? Pull the drivers seat out?
 
If the BOO is shorted, you'd have brake lights all the time, unless you had multiple problems ...

Well, the cruise control test would just avoid laying on your back.

Yah, I'd find it easier to do a lot of work with the driver's seat out. I don't bend that well ( 5 foot 8, 325 pounds - I just kind of roll in there and out like an overgrown beach ball :D )

BOO first - you can check by disconnecting it, shorting the contacts out in the plug, and seeing if the brake lights lit up then (helps to have someone BEHIND to let you know they're working ... )

The multi function switch - for the 1995, there's a section on how to repair one (including disassembly / reassembly ) both at TCCoA, and at MN12Tech.COM (same article posted both places - MN12Tech has a LOT fewer articles, easier to find there.)

Since you can do that SITTING in the driver's seat, not twisted into a non-Euclidean shape, you may want to do that first. If it IS bad, be sure to note the suffix on the part number on the switch - there's at least three, and two of them aren't interchangeable (the third suffix I've not heard for sure which one it crosses to, or even if it DOES cross ... )

One side note - you can use the same MFS the Crown Vic does. This is nice in that if you want to add cornering lights, the CV had that as an option, the MN12 didn't after 1993. So, a 1995 CV MFS gives you the extra switch contacts, all you need to do is add the wiring and the lights if you wish to have cornering lights. I can see about getting the part # - XR7-4.6 did this on his car (notes over on TCCoA again.)

RwP
 
So, today at lunch, I pulled the drivers seat and sort of rolled under the dash of the car. I'm sure my neighbors enjoyed the show.

After doing a fair amount of digging, the connector on the BOO switch had a frayed wire. I say *had*, as when I unplugged it, the final bit of insulation holding the 2 wires together let go.

Now, I need to find a new connector, as the original one doesn't have any wire sticking out of it to splice to.

As much as I love soldering, as tight as this is, I think this one is gonna get put in with butt splices, unless there's a way to get some slack in the harness!
 
Just wanted to post an update. Borg Warner makes the harness, P/N is PT235, about 7 bucks

Advance and O'Reilley's could order it for me, I couldn't find it at Autozone or Napa.

I'll be back on the road tomorrow. Hooray!
 
Brake lights now work! Unfortunately, the cruise and the shift interlock do not.

Brake lights make it safe enough to operate in my eyes, so at least I can drive again. I'll keep digging on the rest!
 
The cruise may not work because of a misadjusted vacuum dump for the cruise control. Move it a little farther away from the pedal arm and see what happens. If you can get your head down into the footwell while the car is running, you may even hear the vacuum hissing until you get the adjustment right.

Now, the shift interlock, I don't know much about.
 
Brake lights now work! Unfortunately, the cruise and the shift interlock do not.

Brake lights make it safe enough to operate in my eyes, so at least I can drive again. I'll keep digging on the rest!

Hey did you ever get this sorted out?

Just noticed last night my brake lights are not coming on :p...may need to fix those. Since I picked up the car I noticed the cruise would not disengage when pushing on the brake pedal...reading this post it looks like the Brake On Off switch is the culprit.
 
Never checked if SC's have this item. It's called a clock spring located behind your steering wheel. Check your horn if it works then you're ok. If neither works then wahtever our cars used in place of a clock spring has issues.
 
The clockspring came in with the airbag.

If his horn works, it may be the cruise switch itself.

Oh, one thing to keep in mind - you DO have to turn it on after every time you turn the car off. I got caught by that until I read the owner's manual, since my Malibu would stay on until I turned it off ...

RwP
 
Yep my car is a stick.

Everything with the cruise works normally...until you try to deactivate the system using the brake pedal :). I still use it, but to turn it off I have to push the OFF button.

I replied to this thread because the malfunction switch was mentioned which made me a little suspicious of mine. The other day I noticed that when I pushed the hazard button both green arrow indicators in the gauge cluster did not light up as they should. Mind you all outside lights worked fine, it was just the right arrow indicator inside that didn't work (although when turning right...not hazards...the light works perfectly). I noticed that if I wiggled the hazard button just a tad I could see the light coming on...so there may be something fishy going on with the hazard switch too.

My first thing to check is still that brake switch though.
 
CaiFanSC - checking the 1994 EVTM (1995 similar), the BOO (Brake On/Off) switch feeds the secondary junction block, and goes straight out to the High Mount Stop Light and the Speed Control Electronics.

If you have the CHMSL working, but the cruise control not, then it's worth checking the wiring.

If, however, neither the CHMSL nor the "Drop out of Cruise" works, then I'd also check the 15A Stop/Haz fuse (although, if hazards are mostly working, that's probably not it.)

Now, for the hazard - that's part of the multi function switch assembly. There's actually an article on cleaning / repairing it on the TCCoA forums ( http://forums.tccoa.com/showthread.php?t=109143 ) and on replacing it at MN12TECH.COM .

But the cruise control and the CHMSL both are separate of the hazard switch - so you've got two different problems there.

RwP
 
CaiFanSC - checking the 1994 EVTM (1995 similar), the BOO (Brake On/Off) switch feeds the secondary junction block, and goes straight out to the High Mount Stop Light and the Speed Control Electronics.

If you have the CHMSL working, but the cruise control not, then it's worth checking the wiring.

If, however, neither the CHMSL nor the "Drop out of Cruise" works, then I'd also check the 15A Stop/Haz fuse (although, if hazards are mostly working, that's probably not it.)

Now, for the hazard - that's part of the multi function switch assembly. There's actually an article on cleaning / repairing it on the TCCoA forums ( http://forums.tccoa.com/showthread.php?t=109143 ) and on replacing it at MN12TECH.COM .

But the cruise control and the CHMSL both are separate of the hazard switch - so you've got two different problems there.

RwP


Hey, that's a good test! It was supposed to be very rainy where I live today so I had planned to do NOTHING (long week in the office) and although it wasn't as bad as they said...i still don't wanna do nothing :). However, I think I can at least check out if the high mount stop lamp works :).

Also, thanks for the link to the cleaning procedure for the malfunction switch. I'll have to give that a try...worst case scenario I do remember I had at least one 94-95 multifunction switch brand new in box from ford stashed away in my parts bin.
 
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