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2002 z71 Brake lights do not work

T

tron guy

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Jan 18, 2020
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30
Hi guys/gals.  This is my first post here, so if I am in the wrong section or if anyone has insight, I am all for it.


I have a 2002 avalanche, 4wd.

The brake lights are not working when I depress the pedal.  All of the lights in the rear are turned on, or working, but they do not get brighter when I hit the brake.  I didn't realize the lights were on, so I bought some new brake lights.  (can't hurt to have as spares anyway I figure).

Next I changed out the brake light switch .  No change.  I even took apart the original brake light switch to try to fix it (when I thought it was bad).  Man talk about a pain in the A$$ 1 handed job.


Anyway, I thought I read/heard somewhere about the brake light switch being tied in with the cruise control.  I never use cruise control, but it had been working previously.  I tried it today and it is not working.

What is the next logical step?  Am I still back to looking at the brake light switch?  operator error upon installation?
 
There are two electrical circuits inside the brake light switch.

The one for the cruise control seems to be the weaker of the two.

I have had to change out this switch in several GM trucks over the years.

There is a wiring junction box located up inside the rear fender on the passenger side of the truck.

This is a common spot for corrosion.

Crawl under there and have a look.
 
so I have one of those camper shells on my truck so I haven't looked yet.  I need to have someone look later on today.  I will report back. 

On an odd side note, I get the impression that there are 3 fuse box locations on this truck.  I can only find 2.
 
tron guy said:
so I have one of those camper shells on my truck so I haven't looked yet.  I need to have someone look later on today.  I will report back. 

On an odd side note, I get the impression that there are 3 fuse box locations on this truck.  I can only find 2.
Click to expand...

There is a fuse box under the hood, a junction block under the dash, and a fuse box inside the driver side end of the dash (little panel that can be pried out covers it).

Going back to your brake switch install:  If you say the cruise was working before, but now it isn't - I'd say the switch was installed incorrectly, so...while you're back down under the dash by the brake pedal, have a test light handy and see if you are getting power to the brake switch. You might just have a blown fuse...lol  >:D

CarMech1969
 
EXT4ME said:
There are two electrical circuits inside the brake light switch.

The one for the cruise control seems to be the weaker of the two.

I have had to change out this switch in several GM trucks over the years.

There is a wiring junction box located up inside the rear fender on the passenger side of the truck.

This is a common spot for corrosion.

Crawl under there and have a look.
Click to expand...

will do, thanks
 
CarMech1969 said:
There is a fuse box under the hood, a junction block under the dash, and a fuse box inside the driver side end of the dash (little panel that can be pried out covers it).

Going back to your brake switch install:  If you say the cruise was working before, but now it isn't - I'd say the switch was installed incorrectly, so...while you're back down under the dash by the brake pedal, have a test light handy and see if you are getting power to the brake switch. You might just have a blown fuse...lol  >:D

CarMech1969
Click to expand...

I haven't used cruise control in months.  I am quite certain I installed the brake light switch correctly, but you never know, right.  I pulled out my meter and tested every fuse under the hood (fuse box), and they were all good.  I'm not sure which fuse would be bad if it were a fuse. 

 
Take a look at the manual and locate the fuse box on the left side of the dash. You have to open the drivers door to get to it, not hard to miss if you don't look right at it, there is one in there labeled "brake".. Don't know if it's the right one but check it out..



https://www.chevyavalanchefanclub.com/assets/files/resources/model-years/owner-manuals/2002-chevy-avalanche-owners-manual.pdf
 
Randy said:
Take a look at the manual and locate the fuse box on the left side of the dash. You have to open the drivers door to get to it, not hard to miss if you don't look right at it, there is one in there labeled "brake".. Don't know if it's the right one but check it out..



https://www.chevyavalanchefanclub.com/assets/files/resources/model-years/owner-manuals/2002-chevy-avalanche-owners-manual.pdf
Click to expand...

yeah it's a 10 amp fuse IIRC, it tested good with  my meter. 
 
CarMech1969 said:
Now that you've established that the fuse is good, have you checked to see if power is reaching the brake pedal switch?
Click to expand...

I will.  I'm stuck at work.  Just taking the opportunity to post and absorb your guys' input until I can get to testing in a few hours. 
 
I just got home,but did check that the 3rd/upper brake light does NOT come on.


That probably rules out a fuse, and gets us to either voltage at the switch, or corroded connections down the chain? (Both mentioned earlier).  I am going to head out and dive in further, I will report back.
 
Ok I looked at, and wiggled the molex connectors under the right rear fender. 

As far as measuring voltage going to the brake light switch.....am I just setting my meter to vdc and unplugging the harness from the brake light switch and hitting the pairs of pins looking for voltage?
 
On at least one pair of pins there was 12 vdc present. 

Anyone who has changed this switch knows it is a 1 armed job.  At least I can only squeeze 1 arm up there for use.  Had to change the switch with 1 arm, and test the voltage with both probes of my meter in that harness, using 1 arm.  Pretty big pain in the ass. 

So I got nothing now.  I cant unplug the molex connectors under the left rear fender.  Cant figure it out.
 
tron guy said:
On at least one pair of pins there was 12 vdc present. 

Anyone who has changed this switch knows it is a 1 armed job.  At least I can only squeeze 1 arm up there for use.  Had to change the switch with 1 arm, and test the voltage with both probes of my meter in that harness, using 1 arm.  Pretty big pain in the ass. 

So I got nothing now.  I cant unplug the molex connectors under the left rear fender.  Cant figure it out.
Click to expand...
How many pins in the brake light switch connector are getting power?

CarMech1969
 
CarMech1969 said:
How many pins in the brake light switch connector are getting power?

CarMech1969
Click to expand...

No idea.  I didn't look at a schematic (if its even available), to see if 1 wire was ground and the other 5 should have voltage.  Seems like that would be weird though.  I work on arcade games and pinball machines a lot, so logical trouble shooting and electricity are my strong point , if I have one.

It is a near impossible job using a multimeter with 1 hand, controlling 2 leads and the harness. 

If I knew exactly what wires or pairs of wires should have a reading, I could test it again. 
 
I never followed up, but after changing the brake light switch. And everything else, I did to try to trouble shoot.

I am embarrassed to say, both bulbs burnt out at the same time. Somehow when I did logical testing there may have been a short or something and this escaped me. hahahhaha
 
tron guy said:
Hi guys/gals. This is my first post here, so if I am in the wrong section or if anyone has insight, I am all for it.


I have a 2002 avalanche, 4wd.

The brake lights are not working when I depress the pedal. All of the lights in the rear are turned on, or working, but they do not get brighter when I hit the brake. I didn't realize the lights were on, so I bought some new brake lights. (can't hurt to have as spares anyway I figure).

Next I changed out the brake light switch . No change. I even took apart the original brake light switch to try to fix it (when I thought it was bad). Man talk about a pain in the A$$ 1 handed job.


Anyway, I thought I read/heard somewhere about the brake light switch being tied in with the cruise control. I never use cruise control, but it had been working previously. I tried it today and it is not working.

What is the next logical step? Am I still back to looking at the brake light switch? operator error upon installation?
Click to expand...
Can someone please tell me how to get to the brake light switch. It seems to be buried up above the pedal adjustment device and is practically inaccessible. Thx
 
Jamesinalpine said:
Can someone please tell me how to get to the brake light switch. It seems to be buried up above the pedal adjustment device and is practically inaccessible. Thx
Click to expand...

I had to run the driver's seat all the way back, lay on my back in the floorboard and then wiggle my arms up under the steering column as best I could.

No small feat for a 250 pounder like me, I assure you.

But, it can be done.
 
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