brake light problem

2000 chevy s10, 4.3L 2wd automatic.

all lights are working except the brake lights at the rear. The single brake light on the top of cab is working normally. when you step on the brake pedal, the cab mounted brake light illuminates, but the rears do not.

turn signals, taillights, and hazards all work normally. can't seem to find the problem. any ideas?

If the white wire at the multifunction switch shows battery voltage when the brakes are applied, the problem is in the multifunction switch. This thread shows how to clean the contacts: http://www.automotiveforums.com/vbulletin/showthread.php?t=577320 If that doesn't cure the problem, you'll need a new multifunction switch.

thanks for the reply. i'll be doing that tomorrow.

in the meantime, my friend decided that brake lights were more important than turn signals, so i cut off the "high side" wire from the bulbs, and spliced it to the light blue wire that is near the harness @ the rear drivers side bumper.

the light blue wire comes from the cab brake light (directly off the brake switch).

just took the multi function switch apart and cleaned it. didn't fix it. any other ideas?

replaced the brake signal switch at the pedal, that didnt fix it.
on the ignition switch, i checed for voltage at the white wire, didnt want to cut and splice, but i assume it is at the space #3, as it is the 3rd wire. unless things cris-cross inside the switch.
no voltage on that terminal, but the terminal associated with the orange wire (#2) is showing battery voltage at all times
http://a8.sphotos.ak.fbcdn.net/hphotos-ak-snc6/182622_10100215748994130_4907863_60490400_2317634_ n.jpg
http://www.facebook.com/photo.php?pid=60490400&l=db83bfee1d&id=4907863

Provided the white wire at the multifunction switch has battery voltage with the brakes applied, the next step is see if the voltage is going through the multifunction switch.

At the multifunction switch connector:

The yellow with black stripe wire and the dark green with white stripe wire must show battery voltage when the brakes are applied. If not, the switch is faulty.

i wasn't seeing battery voltage at any time on the white wire. the orange was always hot.

i'm gonna assume the switch is bad. the same time the brake lights went out, the horn stopped working. thanks for the advice. we're gonna be ordering a new multi-switch tonight.

on a side not. i'm pretty surprised with how relatively easy it is the get to and remove that switch.

Hold off on ordering that multifunction switch untill you know what the problem is.

If the high mount stop lamp works, it means the stop lamp switch is working. There are two white wires at the stop lamp switch, one goes to the high mount stop lamp and the other goes to the multifunction switch. If you're not getting voltage on the white wire at the multifunction switch with the brakes applied, the multifunction switch is NOT the problem. Look for an open circuit in the white wire from the stop lamp switch to the multifunction switch.

i wasn't seeing battery voltage at any time on the white wire. the orange was always hot.

i'm gonna assume the switch is bad. the same time the brake lights went out, the horn stopped working. thanks for the advice. we're gonna be ordering a new multi-switch tonight.

on a side not. i'm pretty surprised with how relatively easy it is the get to and remove that switch.
Check to make sure your wires and connectors are all good and tight. A little squeeze at the terminal clips can help.

I almost threw $300 away on a Fuse panel because of a burnt wire connector that cost nothing to fix.

Check your wires with an Ohm meter for continuity.

Throwing parts at a problem is not good and Multifunction switches aren't cheap.

so, i'm gonna dive back into this tomorrow...

i just want to be sure of a few things:
the white wire you speak of, i should see battery voltage with the pedal off, but no voltage with the pedal pressed? Which white wire is it? the red or balck arrow in the pic? Also, if it is the black arrow, is that the same as the terminal with the yellow arrow? i was checking for voltage at the yellow arrow (trying not to cut into wires unless i have to) and had zero volts at all times.

thanks again for all the help. i'll be putting a hitch on this thing, once the lights are sorted out, and ill be sure to write up a "how-to"

The white wire must show battery voltage when you push on the brake pedal, and no voltage when you take your foot off of the brake pedal. Check those wires carefully, make sure it is white only, no stripe of any other color, plain white. According to the schematic, there's only one white wire to the multifunction switch.

no voltage on the white wire at the multifunction switch.. assuming i have the right wire

here's what my brake switch looks like...


one white, orange, 2 purple, brown, green, and green
which one would be the wire for the rear brake lights?

http://a5.sphotos.ak.fbcdn.net/hphotos-ak-snc6/168008_10100216805786310_4907863_60506797_3235630_ n.jpg

There are 6 terminals in your stop lamp switch connector, which does not correspond with the schematic. Please post your 17 character VIN, (Vehicle Identification Number) and the wire colors in the connector. If a wire has a stripe, include the color of the srtipe.

At the stop lamp switch: the orange wire should show battery voltage at all times. The white wire should show battery voltage when you step on the brake pedal. (If the high mount stop lamp works, it indicates that the white wire is getting voltage when you step on the brake pedal.) The other white wire goes to the multifunction switch, (for the stop lamps in the rear) and should also show battery voltage when you step on the brake pedal. The multifunction switch splits the signal for the rear brake lights.

i dont have access to the vin right now, its a friends truck and he had to drive it home. it's a 2001 gmc sonoma. 4.3L auto trans. extended cab.

see, at the stop light switch i have wires in this order (as seen in the pic):

white, orange, 2 purple on 1 terminal, brown, lt green, dark green.

no stripes on any of them.

the orange and white wires are working as they are supposed too at the brake switch.

on the multifunction switch, i have 2 white wires. i guess i specifically need to know which harness at the multi switch i need to be digging around. my wire colors don't match yours. the multi switch has 3 harnesses... 2 are plug style, and one (the closest one in the pic a few posts up) is like a direct splice (no plugs). I am seeing voltage on the orange wire at the multi switch, but the white wire next to it shows no voltage. is this the correct white wire? there is another one of smaller gauge on one of the plug style harnesses.

If this is the correct white wire (at the multi switch), can i splice a new one from the switch to the pedal? or do i need to trace it back to the big mass connector near the column?

thanks again for the help.

In your first post you said 2000, so all of the info that i have posted may not be correct. I'll check the 2001 schematic and post back.

yea sorry, found out today it's an '01 :-)

we're taking a couple days off from working on it, so take your time.
i think he may go ahead and buy a multi switch anyways. the turn signal shaft was broken off at somepoint and is currently glued together. he wants to fix that anyways.

2000 and 2001 are similar, but there are some differences.

The orange wire is in connector "A" pin #4. The white wire from the stop lamp switch is in connector "A" pin #1, which theoretically, pins 2 & 3 should between them. The schematic that shows the stop lamp circuits only shows circuits involved with the stop lights at the multifunction switch so I can't say for certain if there are wires connected to pins 2 & 3.

As far as running a new wire from the stop lamp switch to the multifunction switch: yes, that would work fine. I know the harnesses are packed in pretty tight under there so that would be a satisfactory alternative to locating and repairing the open circuit. When you make your connections, use rosin core solder and heat shrink tubing, do not use crimp connectors. Keep us posted.

i've been tearing through the wiring diagrams for a while now, and i think i finally have it all understood. the operation of the multi switch, that is. found a new switch for about $90 online, so we're gonna get it just in case, but from what i understand, i'm losing that white wire somewhere between the brake switch and the multi switch. i'm gonna throw a jumper on there next week and see what happens. that is litterally the only thing that i can see that could possibly be causing the exact situation i'm having.

thanks again for the help, and pointing me in the right direction. i'll let ya know how it goes next week.

in other news, it took about an hour to get the hitch bolted up and was really pretty easy. managed to do it myself :-)

Loss of voltage on the white wire at the multifunction switch is the only thing that can cause the problem you described. Give the white wire a once over if/when you replace the multifunction switch. If you look close, you'll find the problem.

replaced the white wire from the brake switch to the multi switch. voltage is getting to the multi switch and getting lost, so i assume the switch is bad. white wire was also getting voltage at the switch.

so. looks like tomorrow i'll be replacing the multi-fuction switch.

any one ever done this? i know how to get it out of the column, but i'm not entirely sure how to disconnnect the wiring.

In the "How-To" thread for cleaning the contacts in the multifunction switch, it shows how to remove it: http://www.automotiveforums.com/vbulletin/showthread.php?t=577320 Might want to try cleaning it before you replace it.... could save you some serious cash!

yea i've seen that, and used it to take the switch off the column, cleaned it out and everything with no luck. i'm guessing an internal solder joint or something has gone bad.

On a strange note, there is a recall on my 2001 blazer for the hazard switch carrier going bad, causing these exact symptoms (center high mount stop light works, but not the rear brake lights). HOWEVER, i'm working on a 2001 GMC sonoma, and there is no recall, even though the multi switch AND the hazrd switch are the same part numbers.

but more specifically, i was looking for some pics of where/how the harnesses plug in. i have the new one in the box, but last time i took the column off, i dont remember seeing where/how it all plugs in.

i'll take some pics while i do it tomorrow, and add them to that thread.

woooohoooooooo!

replaced the multifunction switch this morning, and it fixed the problem. I now have brake lights AND turn signals again! I'll add the steps for final removal to of the multifunction switch to the cleaning thread, unless you would prefer i start a new one.

And thanks for all the help! I feel good about the fact that I carried out a full diagnosis/testing before dropping the money on the part.

Good job, glad you got her fixed and thanks for posting back! Add your pics, and anything else pertainiing to the switch, to this thread.

unfortunatly, i couldn't get any pics, but here's a step-by-step for it. maybe i'll get some pics of the basic stuff from my blazer this weekend. I have to add, i've taken this column apart so many times, it took exactly 2 hours from start to finish to change out the multi-switch.
I also put this in the multi-switch "how to" thread

Here's the final steps to completely removing the multi-function switch, should it need to be replaced:

1. remove everything as described in the earlier steps
2. remove switch from column.
3. there are 2 small connectors on the pass. side of the column. on is green and plugs in towards the ignition switch. the other is black and plugs in near the back of the shifter. unplug these.
4. remove the sleeve from thh wires, cut any cable ties, and reove any tape that is holding the bundle together.
5. unplug the steering column mass connector. if you trace the wires you'll find it, right at the base of the column. A 7mm bolt holds it in. the bolt will back out a good ways, and bring the harnesses with it. a gentle tug will break the whole thing free. note: all of the dash harnesses (4 i believe) are conected together to make this one large harness.
6. the 2 longer harnesses belong to the multi switch. to get them out, look at the bottom of the harness (the side that goes into the mass connector). insert a small screwdriver between harness and the middle piece to push the harness past the retaining notch, then slide down. (do this with both harnesses).
7. remove the multi switch.
8. bolt in the new multi-switch (so it isnt just hanging).
9. install the harnesses into the mass connector thing. seat it, and tighten the 7mm bolt down.
10. install the 2 small harnesses for the ign switch and shifter. be mindful of where you run them, so the don't get pinched.
11. use cable ties, tape, or whatever to secure everything.
12. put everything else back together and test it.