Please help! Brake lights out!

[KINNEY201]

1997 Ford Explorer XLT V8 5.0 Eddie Bauer

Hi,
I got pulled over yesterday because my brake lights are out. I've checked the fuses, the bulbs, etc. and can't figure out what the problem is. My high upper brake light (above the window) works fine, but I get nothing from the tail lights. My signals work, etc. Can someone please suggest a fix so that I don't get pulled over again tomorrow? Thanks!

I thought of the brake switch (on the pedal), but it wouldn't be that if the upper brake light is working, right?

 

[Donner]

Do the lights work? Just no brake lights?

 

[KINNEY201]

I just bought new bulbs to try, but nothing. How do I get the light to light up other than pressing the brake? With hazards on, all I get are the yellow flashers.

 

[Donner]

check this link... have you check the external and internal fuses?

just hit the lights, and they should all come on if the power is on - engine off... you can also just put something really heavy against the brake pedal, you don't need the power on for that.

http://www.explorerforum.com/forums/showthread.php?t=201954&highlight=brake+lights

 

[KINNEY201]

I've tested the fuses both inside and outside. I still press the brake and get nothing.

 

[KINNEY201]

It most likely isn't the brake pedal switch if the high brake lamp is working, correct?

 

[Donner]

Could be that, but check this link also...

http://www.explorerforum.com/forums/showthread.php?t=180290&highlight=brake+light+connector

 

[KINNEY201]

Okay, when I turn the lights on, the bulbs do turn on. I just don't get anything when the brake is pressed, just the high lamp.

 

[Donner]

It sounds like between your situation and the links, that it is the MFS. I don't know what an MFS is, so I'd hold on a sec and let some answer better. At least we've eliminated electrical problems... that's a good thing. If you know what the MFS is, go for it! I'll check back... good luck!

 

[KINNEY201]

Okay, I'll check on it, thanks!

 

[steventadams]

MFS = multi function switch

 

[KINNEY201]

Will it definately be the MFS, since all my turn signals, etc work?

 

[gijoecam]

Not necessarily....

I need to double-check the schematics for a 97 when I get to work in the AM, but if my memory serves, the power comes from the fuse box, runs through the brake on-off switch, then through the multifunction switch, then to the lights. If you've got power at the fuse (I can't give you the fuse to check without the schematics either) and there's is power into and out of the brake on off switch, then and only then would I suggest the MFS.

However, there are two distinct outputs from the brake light switch... one feeds the CHMSL, and one feeds the MFS. It is possible for one of those two to be bad. I need to check the schematics to pin it down for you, but it may be a simple solution.

Bump the message in the AM and I'll see what I can find.

 

[Donner]

Bump will occur!

 

[KINNEY201]

Thanks.

Update:

I replaced the brake switch. No change.

I then replaced the MFS. No change.

High lamp comes on when brake pedal is pressed only.

Brake bulbs only come on when headlights are on. Not when brakes are pressed.

I'm out of options so any advice or easy fix would be greatly appreciated.

 

[gijoecam]

OK, two questions: Do you have a lamp-out module? And have you done anything up under the driver's side of the dash behind the kick panel?

If the 97 is like my 98 (the earliest I have schematics for here at home), both the CHMSL and both lower brake light bulbs are fed from the same circuit. I need to double-check the 97 schematics though...

Before replacing any of the components, I would have taken 2 minutes with a test light to see if there was power at the bulbs first. Before blindly replacing parts, it's always best to rule out the simple stuff first. You'll need someone else to hold the pedal while you check for power at the sockets. Then, I'd start at the fuse, working my way to the brake pedal switch, then the MFS, checking for power both in and out, then work my way back from there.

I'm currently thinking it's either a problem with a splice, or a ground issue. Are you sure it's not the bulbs? They're supposed to be a dual-filament bulb... One comes on with the parking lights, the other comes on with the brakes....

-Joe

 

[KINNEY201]

All of the fuses and bulbs were tested before any of the parts were replaced. We worked closely with the auto parts store making sure that this was done. The bulbs were also purchased at the parts store, matched correctly to the model of the truck. As I said, the bulbs do illuminate when the parking lights are on. I've checked the wiring the best that I could and did not see any splices. Nothing has been done thus far under the dash to cause it. Bulbs and fuses have been checked, checked, and rechecked. Hope this helps, thanks!

 

[gijoecam]

Well, the first thing on my list this morning when I got to work was to check the schematics real quick and post a solid reply.... Until I got to work and realized that today's a holiday and I'm off. Boy, did I feel like a dunce!!

The answer will have to wait one more day... sorry,....

 

[Donner]

work must be fun! forgot you had a day off, lol!

Is it possible to disconnect the (I haven't a clue) points where the break lights attach to any control point? (Did the vehicle go through water, mud, snow? Any hard braking?) Could these things affect it?

 

[gijoecam]

OK, got the schematics in front of me....

Fuse 13 in the interior fuse pane feeds the entire brake light circuit on a 97. Then, power flows through the brake light switch, in via the LG/R wire, out via the LG wire to a splice that feeds power to a whole bunch of things including the rear lights, CHMSL, ARC, cruise control servo, clutch pedal position switch, central timer, shift lock, PCM, and 4WABS module.

A critical question is whether or not you have a lamp out module? If so, that's where I'd start. The LOM is the only possible thing between the splice where it sends power to everything else and the brake light bulbs. Do you have power at the brake light bulb sockets? That's really the first place to check... Take a 12V test light or DMM, ground it to an exposed piece of metal, and probe the socket and the wires. I'm thinking that it's either a bad Lamp Out Module (if it has one), a bad connector/broken wire, or a bad ground.

Just thinking back... you said it works with the parking lights turned on, right? That's leading me to think it's a bad ground... with the parking lights on, maybe there's an alternate ground path back through the parking light circuit that doesn't exist with the parking lights off??

If I was there with a test light and DMM in hand, tracing the problem would take all of 10 minutes... Let us know what you find.