i have an 03 Blazer and the top brake light won't light. i can see a small crack so my suspicion is that moisture got in there and messed it up. i can see some moisture as well. i took the light off but the wires run into the top of the truck. i dont see a plug or anything i took the interior molding off inside and dont see the wire or anything that i can get at to test if i am getting voltage to the light. not sore how to change it out. i am going to try to check the fuses and or relays hopefully the light is fine. we'll see. id rather change a fuse than a 50$ light. fingers crossed

 

There is a plug behind the grommet where it goes through the metal at the top of the window. You should be able to get to it under the rear most plastic roof trim(one with the dome light in it)

 

You can get this light from a pull it yard for 5 bucks.

 

i just tried to check the fuses. there was a place in the relay/fuse box for CHMSL but no relay. cant find any other places to check be it under the hood or inside the drivers side door.

i tried getting at a plug through the trim piecs where the trunk light is but i dont see any access from there. the wire for the brake light seems to go through an upper part of the roof.

 

under the hood in the fuse box there is a spot for CHMSL shown on the diagram but there is no relay in the specified location. i tried using the one for the horn to test the brake light but it doesn't fit. i also looked inside the drivers side fuse box but i dont see anything that specifies the brake light. i believe the CHMSL is supposed to be the center high mount stop light but, i am not sure. is there supposed to be a relay or something there?

 

same problem on 99 blazer. The cover of fuse box lists a CHMSL spot but there are no contact spots to put any relay into. There are 4 holes but 2 are just openings in the plastic. Does the CHMSL relay supposed to have 2 contact points? There is no way to put a 4 contact relay there. I tried to put the horn relay there and only 2 prongs go in the other 2 are just empty holes. The 2 regular fuses are there and where they should be the TRHMSL and the VHMSL both fuses are good. Is it a common thing that the actual light goes bad, afterall I am told they are LED and everyone says LEDS last 100 years because they are not bulbs. Very interested in hearing on how to correct this. I was thinking of cutting into the tail light brake lite and running a wire up to the HMSL. Do you think that would work?

 

Just weasel the grommet out with a dull tool after spraying with WD40 and pull the wire gently and the plug will appear,but I am only familiar with the older split gate design (95-98),not the newer glass or hatch as one assembly where they could be opened as one or independantly of each other. If any one could tell me how to remove the fasteners on a 97 split gate that are just spinning,I would appreciate the input. I posted about this several weeks ago and got no responses. Thanks!

 

Led lighting isnt as good as people make it out to be, its more complex and much more prone to failure , still in its infancy stages in the us auto world.