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Discussion Starter #1
I searched extensively and found nothing related to my problem, so here goes my thread:

I have a 1995 Chevy C1500 W/T 4.3L w A/T. When the brake pedal is depressed All of the brake lights (left, right, & third brake lights) flash on for just a half-second, then they go out even thought the brakes are still depressed. So, this doesn't appear to be the bulbs, or they wouldn't light up at all. Doesn't seem like it could be the brake light switch, or they wouldn't come on at all. I wouldn't think that the circuit boards would cause this either. When I laid down under the dash to look at the brake light switch, I heard a clicking sound when the brake pedal is depressed. The brake light switch looks like it would be a bear to replace, as I can only barely see it and can't hardly reach it either. I have not bothered to check my Chilton manual as I didn't think this kind of problem would be addressed in it. Sounds like a relay clicking, but I can't tell. I just figured the easiest and cheapest way would be to ask on this forum. I can use hand signals for now or just tap the brakes in rapid succession to let people behind me know that I am stopping, but I don't want to do that any longer than is absolutely necessary.

Sorry I haven't checked the obvious like the bulbs, fuses, & circuit boards, but I figured that I wouldn't even be getting the brief flash if any of these were the problem. It also seems like if it were a relay that it would either work or not, instead of just flashing on for a half-second. Any help would be appreciated!
 

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Check your wiring, sounds to me like a bad ground. pretty sure the ground for the brake lights is right near the light ass'y.
 

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If its not a grounding issue as mentioned above, It may not be keeping the ground. When the brake pedal is depressed check the switch for power with a test light.
 

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Discussion Starter #6
I didn't realize when I started this thread that my 95 truck had a brake light relay; this is the first truck that I have owned that was newer than a 79 model, which didn't have a brake light relay. I checked the relay last night and swapped my AC & brake light relays. I'm still having the same problem with my brakes and my AC still works, so I believe that I have eliminated the relay as being the problem. I also found the source of the clicking that I heard under dash when the brake pedal is depressed. I found the part that clicked, yet I didn't know what it was called. Today I discovered that the name of the part, that makes a loud click when the brakes are depressed, is a Brake/Transmission Shift Interlock (BTSI) Solenoid. Does anyone know if this part can affect the proper function of the brake lamps? I don't ever remember hearing this part click before. If it did click before then I just wasn't paying attention or either I couldn't hear it. When I am lying in the floorboard and press the brake pedal it is rather loud now. Any help would be appreciated.
 

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I'd have to agree with silver. We know there is voltage going to the lights and that the grounds are good, or you would not get a flash.

I've seen lots of household light switches cause the lights to flash as it is turned on, but the lights go out as the switch reaches the full on position.

Of course, the real test is to check the switch/circuit with a meter.
 

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Discussion Starter #15
The problem just dissapeared on my truck. I never did find the problem, but they are working fine now.
 

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I know this post is an antique, but it one of the few post on the Internet I could find when I had the same problem... So I registered and I wanted to add what I found to be the problem after tons of troubleshooting in hopes of saving someone else hours of troubleshooting...

For clarification, my problem was the brake lights would pulse on for a moment when the brakes were pressed but then go out, turn signals and all other lights worked fine... After replacing the brake switch, I lost all brake lights, obviously due to me moving the wires around under the dash...

Anyway if you follow the brake switch wiring harness from the break switch connector upwards (it's zip tied somewhere up under there) you will find another connector about 8" up that brake switch harness whip, it was at this 2nd connector that several of the wires had either simply cracked and split due to the steering column being adjusted or they had rubbed against something under the dash cutting little slits in the wire insulation... All in all 4 of the wires insulation was cut/cracked and the orange wire was nearly cut/broke in half... After wrapping all the wires individually with electrical tape, splicing the broken orange wire and giving the entire whip a liberal wrap of more electrical tape the problem was fixed... Note, I had to remove the lower trim and part of the lower metal under the steering column as well as moving some duct work to be able to get at the 2nd connectors location to split it apart for repair, this assumes you have not dropped all that already to get at the brake switch...

This 'broken' or 'breaking' wire explains when the issue comes and goes for some, until the wire brakes entirely...
 

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(1998 GMC Sierra) I was having the same problem. Barely touched the brake and my taillights and 3rd brake would come on for a split second and disappear. I traced the wires from the brake switch and the wires were split. Tapped them back together and working like a charm. Had to remove bottom plastic, some metal and a bar and drop steering column. 30 minutes total.
 

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(1998 GMC Sierra) I was having the same problem. Barely touched the brake and my taillights and 3rd brake would come on for a split second and disappear. I traced the wires from the brake switch and the wires were split. Tapped them back together and working like a charm. Had to remove bottom plastic, some metal and a bar and drop steering column. 30 minutes total.
If my memory is correct that is pretty much what mine looked like, hopefully, this old thread continues to help others...
 

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If my memory is correct that is pretty much what mine looked like, hopefully, this old thread continues to help others...
I just went through the same issue with my 99 Suburban. It doesn't get used alot, so when I noticed my brake lights acting funny, I thought it could just be the brake light switch. Most of the time if I just touched the pedal, they would flash briefly, then most of the time I would have to push alot harder than it would take to stop the vehicle before they would come on. If I drove it alot, it seemed like it got better and seemed to almost be normal the more I used it. I replaced the brake light switch with help from a you tube video. The only difference from what I did to remove the switch from what the guy in the video did, was I popped the switch up off of the brake booster rod then keeping a slight bit of pressure like I was pushing the switch off of the rod, I spread the slot in the retaining clip. That made the switch pop the retaining clip right off. I used a 7/16 box end wrench to reinstall the clip after I put the new switch on. It didn't fix my problem though. So I pulled down my dash panel and found the next plug back from the switch in the brake switch harness. It is maybe 5 inches away from the switch. The whole issue was where the wires go over top of the shaft for the brake pedal, over time it rubs the underside of the steering column support brace and the wire either rubs through or breaks. I had to disconnect the brake light switch again and left the harness attached to it and pulled it apart at the connection that comes down by the column. My white wire was broken and the ends would intermittently make contact. The break in my wire was too close to the terminal for me to splice. I had some other wiring from some old projects in my stash, and found the right gauge wire with the correct terminal I needed and repinned the connector and spliced it into the harness and taped it up all nice and cozy. Now I can barely touch the pedal and they work correctly the whole time. I'm glad this post helped me locate my wiring issue and hope it helps someone else as well.
 
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