Brake lights not working

NMviperguy

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Hello everyone!

Been awhile since I've posted. I own a 2004 SRT-10. I did a search for brake lights not working and couldn't find anything specifically for this issue. I was told about 9 months ago my brake lights weren't working by someone in traffic. I drove her home and completely forgot about it. I've driven her a hand full of times since then, but shes mostly been in hibernation due to the pandemic and me not driving much. I finally remembered yesterday and have been working to resolve the issue. It is all 3 brake lights so I figured it was the brake light switch. Swapped it out today and no luck. I checked the fuse which looked good. To make sure, I swapped it with the same size known good a/c fuse and still nada. I got some bulbs and swapped them out to no avail. I don't know where to go next. Any ideas or direction would be much appreciated!

Thanks,

Jesse K.
 

MoparMap

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The only other thing that really comes to mind for me at that point would be the harness, but that's a longshot. I'm guessing maybe there's a main connector where all the rear pigtails come together, but I'm not convinced it's actually set up that way. I know there are connectors for each tail light as I had to replace one of mine after breaking a tail light, but I don't recall how far that harness went. I wonder if you have a bad connection or a break in the harness at the foot switch? That would probably make more sense.
 
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NMviperguy

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I did check the plug into the brake light switch itself and it seems ok. Unfortunately electrical is not my strongest area but I think you are right. If everything else seems right I may have to trace the wires and see if there is something frayed or broken somewhere...
 

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Yeah, for all of them to not be working at once that certainly seems like a fuse or switch problem. I know you said you checked them already, so guessing it might be between them at this point. I suppose there's a really random chance there is something wrong with the BCM where it's getting the signal from the switch but not turning the lights on, but that's hard to say. If you know anyone with a DRB III you may be able to check that.
 
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NMviperguy

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Well... Update, I checked the full undercarriage of the car for any loose or frayed wires. Everything checked out. Checked under the hood, all good. Went back to the brake light switch itself and disconnected the wire harness. It has 4 wires going to it. I connected a test light to the ground on the wire harness and checked the other 3 wires to see if it was getting power. It is, so I then used 2 test wires to connect the remaining 2 wires in the harness to the hot wire and **** my brake lights are on... This tells me that the culprit has to be the brake light switch right? Nope. I just warranty swapped the brake light switch and still no brake lights when pressing the pedal... I'm at a loss at this point. I can verify ground and hot are good and if I connect the other to to the hot the brake lights work. This tells me wiring after the switch is also good. Where do I go from here?

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MoparMap

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I'd still see about checking the switch independently of the circuit. Get a continuity tester on it and cycle it a few times to see if it's actually making/breaking contact correctly. Just because it's a new part doesn't mean it's good. I've learned that myself a few times. I'd also double check the voltages you are seeing on the hot side. It could be that the switch has enough resistance that it's dropping the voltage below the point where the lights would want to turn on, but with a direct wire it doesn't. I know I had a pretty wild issue on my 67 Dart that I completely redid the electrical on where I had a fuse that just started to blow, but didn't go all the way. It still made contact, but was only reading about half voltage. I was baffled how I was getting that voltage until I looked at the fuse.
 
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NMviperguy

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I'd still see about checking the switch independently of the circuit. Get a continuity tester on it and cycle it a few times to see if it's actually making/breaking contact correctly. Just because it's a new part doesn't mean it's good. I've learned that myself a few times. I'd also double check the voltages you are seeing on the hot side. It could be that the switch has enough resistance that it's dropping the voltage below the point where the lights would want to turn on, but with a direct wire it doesn't. I know I had a pretty wild issue on my 67 Dart that I completely redid the electrical on where I had a fuse that just started to blow, but didn't go all the way. It still made contact, but was only reading about half voltage. I was baffled how I was getting that voltage until I looked at the fuse.

I did try the continuety test on the original switch but I really am horrible with electrical and saw the ohms reader jump up... Which made me thing that my original may have still been good. I definitely think its a connection issue. I was able to get ahold of a 3rd switch and tried it not connected to the car with no change. A buddy of mine suggested I replace the wire plug for the switch since we can make the brake lights go on when we bypass the switch. I ordered it yesterday. It should arrive today. I hope this works!
 

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Wow, that is really bizarre. The only other thing I could imagine would be the turn signal switch. I have this issue on my 67 Dart. The left brake light on it likes to not work all the time and if I wiggle the turn signal switch just a bit it will usually fix it. I don't remember how the earlier cars have the turn signal set up though. On my Dart it has to interrupt the brake light because it uses the same bulb for turn and brake, but if it's a separate light on the Viper that might not work that way.
 
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