third brake light
#21
10-14-2007, 07:29 PM
RE: third brake light
Maybe they forgot to change it from the 95-97 years...
That, or there was some that had it there, and they didn't bother changing the documentation for the others that didn't have it there...
That, or there was some that had it there, and they didn't bother changing the documentation for the others that didn't have it there...
#22
02-01-2009, 03:32 PM
RE: third brake light
Did you ever figure this out? I just went to have my car inspected and it failed because this light was out. I tried changing the fuse and it didn't work. Also, does anyone know if this light is actually required to be working for inspection? Would it pass if I just plain removed it? Thanks! 
-Ralph
-Ralph
#23
05-06-2009, 11:42 PM
passed
I don't know how, but I got lucky going through inspection. They passed me even though my third brake light was out! They just said make sure you get it fixed asap.- Wow - finally I caught a brake. Now, I just need to figure out how to get it working....
Now, I just need to figure out how to get it working....
#24
05-09-2009, 09:22 AM
Check the wires coming from the light where they go into the truck. I had my original ones wires actually break there and the one I pulled out of a yard were bad there as well. I simply cut a short section out of the wires and soldered them back together...a little shrink wrap and all was good.
The reason they break there is from the opening and closing of the hatch...to much bending over time.
The reason they break there is from the opening and closing of the hatch...to much bending over time.
#25
12-22-2009, 11:00 PM
How to Troubleshoot; With Pics
I decided to troubleshoot my third brake light today, and I brought my camera. Here's the steps so far. The following pertains to a 2000 Chevy Blazer LT, 4x4
1. Pull fuse from fuseblock under hood. The one that is labeled VEHSTPL (I think) is the one you want to pull and check. Replace fuse if bad. If not, continue.
2. Open up your rear hatch, and pull the center piece of the plastic molding down that holds your cargo bay flood light. It may take a bit of force to remove it, but its only held on by compression clips. Take care once it does come off, the flood light wire will be attached to your cabin frame. Once the molding is off, disconnect the wire connected to it by using a small blade tip screwdriver. Set the molding aside.
2a. Find the yellow and black wires that come from the wire harness inside your frame. There will be two areas to view in; one is where the floodlight housing is recessed into. If you look up and to the left, you'll see the wire bundle. One is for the floodlight and the other is for the brake light. The other way to find the wires is to gently pull down on your roof cloth inside the cabin. There will be a slight access to the left just offset from center. If you find the wires, feed them through the access hole so the wires are in plain view, coming out of the floodlights recessed hole.
(Before moving wires to middle rectangle hole)
(I accessed them by reaching my fingers into the cloth ceiling and pulling the connector out. Eventually I moved it to the hole for easier access.)
2b. Use a small blade tip screwdriver and disconnect the plug to the brake light.
2c. Use something (or someone) to push your brake pedal down to keep the brake lights on.
2d. I used a multimeter with alligator clips and tested for VDC at the brake light wire connector. (Gray and Black) You can use a test lamp also. When I first connected the clips I got a spike of around 12VDC. One of the clips fell off, and when I went to reconnect, I completed the circuit at the connector and it sparked, shorted, and blew the fuse. Good enough for me, I was certain power was being applied to the light correctly. Continue to step 3. If your not getting power, check your wires for breakage. If there is no obvious breakage, there is a relay in the system you can check; continue below. Release the brake pedal.
2e. Most models have the relay in the under the hood fuse block. It sits in the bottom right, and is the same relay as the horn. It will be labeled CHMSL. Pull the CHMSL relay and the HORN relay and swap them. After the swap ops check the horn and brake light. Is the horn inop? Replace relay. If it works, troubleshoot wiring between fuse block and battery connection, and fuse block to rear light connector. Repair wiring when found.
3. If you're getting power at connector, remove the LED light. Once removed, you can pull it open and if your careful, not damage the rubber seal underneath it. Remove rubber grommet holding wires that pass through vehicle frame to the outside hatch. Carefully pull out one side of the LED lights that contain the circuit board. Once out, look at the board for any broken wires, resistors, or diodes. Check wiring. Obvious damage indicates that you will need a new light. If you want to ops check the LEDs, plug the connector to a 9V battery and it will illuminate. If it doesn't, the LED strip is broken and requires replacement.
(Removing the rubber grommet)
(LED Bar removed, LED Board removed from bar housing. Mine was cracked which allowed moisture to get in)
(The culprit... a blown resistor... or something.)
(I jammed a piece of safety wire where the resistor went, and cut off the connector, then pressed the wires on a 9V battery. Yay christmas. )
4. Replace LED strip and reconnect everything. Install molding. Enjoy your 3rd brake light.
Enjoy. I hope this helps some other people out. I'm sorry my info on the wires troubleshooting is pretty limited. If its not the relay, the light bar, fuse, or wires out in the open at the hatch, then I would just chalk up the loss of the 3rd brake light. For those without the relay in the engine compartment fuse block (Such as myself-even though the sticker says it should be there) I do not know the exact location of the relay to ops check it. Maybe someone can edit this and provide that information.
Thinking about this post; alternatively, you could just remove the rubber grommet, and if your lucky enough to have some slack in the black and gray wire, you could feasibly pull the connector through the hole where the grommet sits, and troubleshoot without having to pull the plastic molding. Choose your method!
1. Pull fuse from fuseblock under hood. The one that is labeled VEHSTPL (I think) is the one you want to pull and check. Replace fuse if bad. If not, continue.
2. Open up your rear hatch, and pull the center piece of the plastic molding down that holds your cargo bay flood light. It may take a bit of force to remove it, but its only held on by compression clips. Take care once it does come off, the flood light wire will be attached to your cabin frame. Once the molding is off, disconnect the wire connected to it by using a small blade tip screwdriver. Set the molding aside.
2a. Find the yellow and black wires that come from the wire harness inside your frame. There will be two areas to view in; one is where the floodlight housing is recessed into. If you look up and to the left, you'll see the wire bundle. One is for the floodlight and the other is for the brake light. The other way to find the wires is to gently pull down on your roof cloth inside the cabin. There will be a slight access to the left just offset from center. If you find the wires, feed them through the access hole so the wires are in plain view, coming out of the floodlights recessed hole.
(Before moving wires to middle rectangle hole)
(I accessed them by reaching my fingers into the cloth ceiling and pulling the connector out. Eventually I moved it to the hole for easier access.)
2b. Use a small blade tip screwdriver and disconnect the plug to the brake light.
2c. Use something (or someone) to push your brake pedal down to keep the brake lights on.
2d. I used a multimeter with alligator clips and tested for VDC at the brake light wire connector. (Gray and Black) You can use a test lamp also. When I first connected the clips I got a spike of around 12VDC. One of the clips fell off, and when I went to reconnect, I completed the circuit at the connector and it sparked, shorted, and blew the fuse. Good enough for me, I was certain power was being applied to the light correctly.
Continue to step 3. If your not getting power, check your wires for breakage. If there is no obvious breakage, there is a relay in the system you can check; continue below. Release the brake pedal.2e. Most models have the relay in the under the hood fuse block. It sits in the bottom right, and is the same relay as the horn. It will be labeled CHMSL. Pull the CHMSL relay and the HORN relay and swap them. After the swap ops check the horn and brake light. Is the horn inop? Replace relay. If it works, troubleshoot wiring between fuse block and battery connection, and fuse block to rear light connector. Repair wiring when found.
3. If you're getting power at connector, remove the LED light. Once removed, you can pull it open and if your careful, not damage the rubber seal underneath it. Remove rubber grommet holding wires that pass through vehicle frame to the outside hatch. Carefully pull out one side of the LED lights that contain the circuit board. Once out, look at the board for any broken wires, resistors, or diodes. Check wiring. Obvious damage indicates that you will need a new light. If you want to ops check the LEDs, plug the connector to a 9V battery and it will illuminate. If it doesn't, the LED strip is broken and requires replacement.
(Removing the rubber grommet)
(LED Bar removed, LED Board removed from bar housing. Mine was cracked which allowed moisture to get in)
(The culprit... a blown resistor... or something.)
(I jammed a piece of safety wire where the resistor went, and cut off the connector, then pressed the wires on a 9V battery. Yay christmas. )
4. Replace LED strip and reconnect everything. Install molding. Enjoy your 3rd brake light.
Enjoy. I hope this helps some other people out. I'm sorry my info on the wires troubleshooting is pretty limited. If its not the relay, the light bar, fuse, or wires out in the open at the hatch, then I would just chalk up the loss of the 3rd brake light.
For those without the relay in the engine compartment fuse block (Such as myself-even though the sticker says it should be there) I do not know the exact location of the relay to ops check it. Maybe someone can edit this and provide that information.Thinking about this post; alternatively, you could just remove the rubber grommet, and if your lucky enough to have some slack in the black and gray wire, you could feasibly pull the connector through the hole where the grommet sits, and troubleshoot without having to pull the plastic molding. Choose your method!
Last edited by ravenhurst; 12-22-2009 at 11:04 PM.
#26
12-23-2009, 02:19 PM
I'm also having problem with the third stop light, Ive checked the fuse and this was not the problem ... but I donīt have any relay located at the position as shown at the fusebox ... there seems not to be any wirer's either at this position.
#27
12-24-2009, 09:59 AM
Your next best course of action is to pull the connector to the LED assembly at the back of the truck and see if VDC exists at chassis side connector when the brake is applied.
#28
12-24-2009, 04:26 PM
Yea I guess so, I will take care of this after these weekends and life turns back to normal again.
#30
12-25-2009, 11:04 PM
I'll put my money on this being the problem. I had to replace mine due to the same thing. The dealer wanted an a$$load for a new one. Luckily a buddy had quite a few stored in his basement, so he sent me one for free. I didn't even have to cover shipping.