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Brake Light Switch Problem and now no power!!! HELP!!!

H

Honey24

Full Member
Joined
Jun 24, 2009
Messages
12
I have a 2004 Avalanche. Recently I noticed my brake lights not working. The blinkers, third brake, and reverse lights all work. The fuses and bulbs have all been checked. The problem has been narrowed down to the brake light switch which we attempted to replace yesterday. Once the new brake light switch was in place the brake lights just stay on. As we were checking the connection we tried to crank the truck and it was dead. A few lights come on inside the truck but very dim. Any suggestions???
 
I would think it has something to do with the switch, that made the stoplight stay on, check the alignment of it. If you were listening to the radio while working on the AV and how long were the brakelights stuck on that may have drained the battery.
 
Ok guys...I posted about a week ago about my brake lights being out. Both of them are out. The blinkers, reverse lights, flashers, and top brake light all work properly. All relevant fuses and bulbs have been replaced. The brake lamp switch has been replaced. The junction block at right rear of vehicle has been cleaned and put back in its place. I am at a loss. Is there something that I am missing?? Please help...I can't be without brake lights any longer. Also...this is a 2004 AV that I bought used. The only noticable mod is the Viper alarm.
 
Have we test for voltage? I have had bulbs look good. But they were bad.

I wouldn't had thought the brake switch was bad. If the Center Light was working.
 
Do you get voltage at rear sockets?
If not...

start going back towards front checking voltage along the way...
 
So you have voltage at socket but bulbs do not work?

then replace bulbs
 
Replaced bulbs already. Bulbs work for blinkers and tail lights just not brake lights. Third brake light (at top middle) works as well.
 
Wait.
do you have voltage at socket when the brake light is supposed to be on?
then you are using wrong bulb these are dual filament bulbs

remember not all 4 rear tail lights are for the brake light..

i think it is the top ones only or maybe bottom I forget
 
Both top and bottom bulbs should be 3157.
Both are double filament.

Top is tail/turn, Bottom is tail/stop.

Question: Are you the original owner of the 2004?
 
All 4 of the bulbs are 3157. I was pretty sure I had that right.

My ex-husband tried to test the voltage to the socket again - which blew the 25a stop lamp fuse in the fuse box under the hood. We replaced that fuse and called it a night.

I am not the original owner of my beautiful white Avalanche. I bought it exactly 2 years ago. It was in "like new" condition and had obviously been well cared for. It is my favorite vehicle of all I have ever driven.

The only problems I have had (other than my brake lights!) are:

1. The driver's side A/C actuator going out - causing the air to blow very hot occasionally. I turn off the motor and restart and it's fine.
2. Occasionally my speedometer goes nuts - says I'm going 120 whengoing 70 or says 0 when going 70. It eventually stops on its own.
3. Occasionally my clock and radio stations reset for no reason.
4. My check engine light comes on for brief times - then goes off.
5. Mt driver's side DRL is out.
6. My driver's side license plate light is out.

My job requires a lot of travel so I am on the road everyday in my Avalanche and I have got to get these brake lights working. I'm trying my best to figure it out (with help) and avoid taking it in for repair. I am learning a lot and appreciate all the input from all of you.

Thanks,
Lynda
 
Ok,
You didn't notice any unusual wiring when removing the taillight on both side: Like any extra wirings?

I'll check the circuit diagram I have. Unless someone else look into that.
Blowing the 25amp Veh Stop fuse, when applying the brakes is definitely a short somewhere.
 
The fuse blew when he went to touch the ground wire to the body of the truck...I didn't see where he touched it to. He is an electrician, but not a mechanic...could he have done it wrong?
 
My info is for an 03'.

Well here goes depending on which side you are testing:
Left wiring color:
Light Blue is Stop Voltage
Brown is Left Park Lamp Voltage
Black is Ground

Right wiring color;
Only difference is Right Park Lamp Voltage is Brown/White

So just test for voltage between Light Blue & Black wire, with someone stepping on the brake.

About the fuses:
STOP 25 Amp is Hot at All Time and feed into the Stop Switch.
There are two different setup for RPO JF4 or without JF4 options. Check glove box label for that.
I'm assuming the difference is adjustable brake pedals. But someone can check that and post here.

CHMSL 10 Amp works only for the top brake light.

Veh Stop 15 Amp feed to the junction block mounted on the rear passenger side above the tailpipe.

Brake 10 Amp is Hot in Run feed into the Stop Switch.

BTSI 10 Amp is Hot in Reverse and feed into the Stop Switch.

I would also recheck the junction block.

Most of the troubleshooting point to the Stop Switch. But you have replaced that.

Hope this helps.
 
My guess is the flasher relay unit behind the kneeboard (just in front of your left knee.)  All the power for those lights comes from there.  Mine went bad last year.
 
Trey,

My daughter and I got the flasher relay / flasher module off my Avalanche. We took her identical (same GM part #) relay off her Trailblazer and tried it on my Avalanche. No dice. Is it ok to test it that way? By the way - her brake lights worked with her flasher module in my Avalanche! We were so disappointed! Both of us felt that was the problem. We haven't followed up on the wire checking thing. Wires are a little more complicated to us than taking a part off and replacing it. We're going to get a meter to check voltage. Someone's suggestion of the turn signal switch may be our next project. Can a dealership easily diagnose electrical problems like this? Is it expensive? My friends are making fun of me for not taking it in for repair! I really do need to get it repaired soon - as much as I am on the road with my job........

Thanks,
Lynda
 
We just read somewhere that if that possibly the stop lamp switch / brake switch was not properly grounded -causing brake lights not to work. Can anyone tell me how to check that out? Sorry this is taking so long. I'm really getting almost exasperated enough to take in in to the dealership. ALMOST! $$$

Thanks,
Lynda
 
PLease check for voltage at REAR BRAKE LIGHT BULB Socket when someone presses foot on brake.

above you state you have voltage yet lights do not work which just does not make sense
 
Honey24 said:
We just read somewhere that if that possibly the stop lamp switch / brake switch was not properly grounded -causing brake lights not to work. Can anyone tell me how to check that out? Sorry this is taking so long. I'm really getting almost exasperated enough to take in in to the dealership. ALMOST! $$$

Thanks,
Lynda
Click to expand...
The brake switch only provides 12v to the bulbs. Do you have 12v on the light blue wires when the brake petal is pressed? Do your running lights work? If your top brake light works then your switch is good. If your running lights work then the ground to the bulb is good. You need to trace back until you find the 12v.

The power from the switch comes in to the junction block (on the rear inner fender) on connector C1 pin B and out on C2 pin D to the left light and C4 pin A to the right light.
 

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ygmn - I am going to get someone to check the voltage to the socket when the brake pedal is pressed. I don't understand electronics (yet) and thought voltage was good because running lights and turn signals work.

ItsStopher - I agee. The  switch is good. Now, where is the light blue wire? I'm going to check the junction block again.

Thanks guys.
 
Honey24 said:
ygmn - I am going to get someone to check the voltage to the socket when the brake pedal is pressed. I don't understand electronics (yet) and thought voltage was good because running lights and turn signals work.

ItsStopher - I agee. The  switch is good. Now, where is the light blue wire? I'm going to check the junction block again.

Thanks guys.
Click to expand...
the light blue wire is on the bulb socket and goes to the junction block
 
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