Brake lights not working

bneal007 · May 4, 2006

Well I removed the multifunction switch found the stoplamp wire made sure the connection was good and it was but still no brake lights or cruise control. I also test the stoplamp wire for power and there was. I am totally stumped HELP!!!!!!!!!!

Mike97gt · May 5, 2006

Ok I was just looking at the wiring diagram and I have one question..

Is your thrid brake light working, make sur eyou have good bulbs in it and test it, becuase the circuit is divided, if you have power to the thrid brake light then your problem is after splice s323

Also I need you to see if your getting power to the brake pedal switch. that one you replaced, tell me if you have power to it, and what happens when you push the pedal down, do you have power on the other wire.

bneal007 · May 5, 2006

svttech76 said:
Ok I was just looking at the wiring diagram and I have one question..

Is your thrid brake light working, make sur eyou have good bulbs in it and test it, becuase the circuit is divided, if you have power to the thrid brake light then your problem is after splice s323

Also I need you to see if your getting power to the brake pedal switch. that one you replaced, tell me if you have power to it, and what happens when you push the pedal down, do you have power on the other wire.

ok the third brake light is not working, I hooked a voltage meter to the third brake light and got .01 volts with no change when i press the pedal, I did the same on the brake switch and got 11.97 volts but when i pressed the pedal in the voltage drops to zero. I will try the bulbs in the third brake light but they do not look blown.

n0v8or · May 5, 2006

Mike, if he has no 3rd brake light or Cruise Control, there do not seem to be many possibilities left (assuming at least one of the 3rd brake light bulbs is good). The voltage measurements you recommended at the brake pedal switch are the key to isolating this.

Bneal007, wire colors at the brake pedal switch should be green with a red stripe and red with a green stripe. The former should read ~12V relative to chassis at all times, even with the ignition off. The Red with green stripe should read ~12V only with the brake pedal depressed.

No 12V on the green/red means an "upstream" problem (fuse 33, broken wire, bad splice 207). Both readings good means a "downstream" problem (loose connector most likely).

Another possibility I have seen once before is a short in the tail light circuit. It pops a fuse every time the brake pedal is depressed. So, after finding and changing the bad fuse, you expect the lights to work, but it just blows the fuse again. Since the fuse was already changed, you assume it must be something else.

n0v8or · May 5, 2006

Oops, I just noticed the last sentence in message #23. The switch wire voltage (I assume it is the green w/red stripe) is ~12V but drops to zero when the pedal is depressed (switch closes). This suggest a high resistance somewhere between battery and the brake pedal switch. It can pass enough current for the meter, but not to light a bulb.

Next test I would do is to check if both sides of fuse 33 remain at 12V with the brake pedal depressed. If you don't have a helper, you can wedge something between the seat and pedal to hold it down.

bneal007 · May 5, 2006

n0v8or said:
Oops, I just noticed the last sentence in message #23. The switch wire voltage (I assume it is the green w/red stripe) is ~12V but drops to zero when the pedal is depressed (switch closes). This suggest a high resistance somewhere between battery and the brake pedal switch. It can pass enough current for the meter, but not to light a bulb.

Next test I would do is to check if both sides of fuse 33 remain at 12V with the brake pedal depressed. If you don't have a helper, you can wedge something between the seat and pedal to hold it down.

I checked fuse #33 and it remained @ 12V on both sides. I also checked the wires on the switch and the red with green strip went to 12V only when I pressed the pedal and the green with red strip stayed @ 12V all the time.

n0v8or · May 5, 2006

Those are all the right answers, but one seems to conflict with message #23. There is the possibility that probing around the pedal switch restored a bad connection, so be sure the brake lights are still not working before going any furthur.

Next place to measure is both sides of fuse 41 (15A, marked "multifunction switch/stoplamps"). This has to be measured with the brake pedal depressed.

Was any work done under the dash just before you noticed the brake lamps had stopped working?

n0v8or · May 5, 2006

You seem cofortable using a voltmeter, so I generated a flowchart to help better understand the troubleshooting process. Current flow is from top to bottom. At splices, the current goes in 2 directions, top-to-bottom and left-to-right.

Battery
Fuse 33
Splice 207 ------> Brake pressure switch ---> Cruise
Brake pedal switch
Connector 232
Fuse 41
Splice 323 ---> Connector 406 ---> Center brake lamps
Multifunction switch
Rear stop lamps

The last set of measurents you reported (at the brake pedal switch) indicates everything is good above and including that switch. This assumes the connector was making contact to both switch terminals during the measurement.

If you measure ~12V at both ends of fuse 41 with the brake pedal depressed, it will mean everythng is OK above and including that fuse.

bneal007 · May 7, 2006

PROBLEM FIXED!!!!! The last sentence in #27 got me thinking. I had a sub and amp installed by a friend he installed a toggle switch down by the hood release latch.but did not see the wires behind the plastic cover so when the hole was drilled one single wire was cut in half. I reconnected now I have all my brake lights!! Thanks to everyone that helped me track down this problem..

02dragGT · Jun 20, 2006

Ok mine turn. I have no brake lights now, my car is a 2002 so I dont know if the info here is the same or not but.... I have 12 volts on both sides of fuse 33, I also have 12 volts at the brake switch in the green/ red wire and on the other wire when pedal pushed, I do not have power at fuse 41.... so is it connector 232 and if so were is that??

n0v8or · Jun 20, 2006

Were the fuse 41 measurements made with the brake pedal depressed? Did you check both sides?

All measurements below the brake pedal switch on the list (of message #28) have to be made with the pedal depressed. I usually wedge something (like an umbrella) betwen the pedal and the front edge of the seat to hold it down.

Connector 332 (I mistyped it in the earlier message) is located just forward of the driver's side door. The plastic kick panel might have to be remove to access it. However, both broken wires and failures at connectors are rare unles someone was recently working in that area or the car was in a flood.

Mike97gt · Jun 20, 2006

go thru the same tests as before. chekc to see if the thrid brake light works.. This is important because the thrid brake light bypasses the multifuntion switch and is directly wired to the third brake light.

I totally forgot to check on this after I gave advice to the other guy. PM me if I forget to keep checking on this.

02dragGT · Jun 20, 2006

I did depress the pedal when checking the voltages at fuse 41, I'll pull the kick panel tomorrow and check that out, really haven't done anywork around there lately. Car has never been in a flood, in fact its never even been in the rain. Third Brake light is not working either. Everything was fine, trailered the car about 50 miles to friends house, drove it 5 miles to a car show, left show and drove back to trailer and a friend that was following me said half way back I loss my brake lights.

A couple other notes car has about 17000 miles on it, cruise quit working about 1 1/2 years ago, last year the dash started doing weird stuff, at start up the guages dont move for about 20 to 30 seconds and then they jump up, sometimes its fine, if its really hot out sometimes the odometer will blank out and then flash and then come back on. Was thinkig it was a battery voltage problem but not sure, the cluster has been changed and so has the computor. Both were done last summer when the car wouldn't restart while dynotuning and programing my SCT chip. When the dash flips out the Traction control light/switch wont work ( have it turned off on a couple of my tunes now)

Dont know if any of that is related or not, right now would be happy just to have working brake lights

Thanks for the help!!!

n0v8or · Jun 20, 2006

If there is no voltage at fuse 41, the center brake light should not be working either. As svttech76 says, this is an important clue.

There are several connectors in the left kick panel area. C332 is square in shape, and has 4 rows of 4 pins each (16 total). Wire colors are (from pins 1 - 16):
Orange / green
Green
Violet
Green / orange
blue / white
tan / red
red / green
white / violet
tan / yellow
grey / blue
brown / pink
green
white / green
green / orange
light green
orange / red

Mike97gt · Jun 20, 2006

ok I think you have the same problem the last guy had. check the wiring after the brake switch, first place I would look is any places where your feet can hit and where the wires go thru the firewall.

If n0v8or does not get to it first I will try and post a more detailed response tomorrow. I can't start somthing liek this now I need to get to bed

02dragGT · Jun 21, 2006

I think I found the problem. I pulled the kick panel to check the connector and that was good so I went back to 41 and check for 12 volts, got nothing pulled the fuse out and checked again to contacts and had 12 volts. Tried 3 good fuses nothing so I tried a jumper wire and they work, pulled the wire out and tried the fuse again nothing, twisted the prongs slightly still nothing. Put one those fuse jumpers on it put it back and and they work. It seems like one of the contacts has spread a little and wont make with a fuse in it. I'll check it again tomorrow and make sure but I think I got it.

Thanks for the help guys, I've never been on a forum were I got good info that helped me fix the problem. I could not have fixed it without your help!

Any Ideas on that dash problem? Where is a good place to get 12 volts switched with the key. I need to power my nitrous and shift light.

Thanks again Ron

n0v8or · Jun 21, 2006

I never would have guessed a bad fuse socket contact; your preserverance and logical thinking was the real reason for success.
I suppose if there is one bad fuse contact, there might be another that is disabling the cruise control. Its worth a look.

Those devices that clip into a fuse holder to give you a free wire with an inline fuse in it are handy for a source of power behind the instrument panel. They avoid the need to cut wires or make splices.
Where do you need a power source for the nitrous kit? Somewhere under the hood?

droptopford 5 0 · Jul 9, 2006

every time i hit the brakes, it trips the fuse... yet i have the same problems when the fuse is tripped( no brake lights, no turn signals, and cruise) could this still be the multi switch ?

Robuilt · Apr 16, 2010

just wanted to share some obvious info.

i bought my cobra in feb of this year. the car came to me with out the brake lights working. i never knew because the tail lamps worked fine. thanks to the courtesy of the local police dept, i was "informed" my taillights were not working. the previous owner "did not know" but as i started looking around under the car, the brake light switch was just dangling there in the wrong position. the pedal was not making the correct contact to activate the switch. it was also missing the black plastic grommet and white nylon bushing. i found those through a fellow stanger on here. i installed the missing parts and corrected the alignment of the switch and there was light!

so, before checking all the wiring diagrams and going crazy, dont forget to check the obvious first.

95mustangbuild · Apr 22, 2017

okay so you guys are probably done with this but recently purchased a 95 mustang v6. Building project.

okay so question is, no tail lights or brake lights. Replaced brake ON/OFF switch, replaced headlight switch( before finding out that the tail lights run through the MF switch), replaced MF switch and my tail lights worked but my brakes did not. Went to put it back together and checked my lights half way through reinstall and i was back to square one, no tail lights or brake lights.

I need help lol.

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