I’m having the common issue of all lights working correctly except when the blinkers are going and I push the brake the blinkers stop. I know the common culprit is a bad ground or a short so I’ve done a fair amount of troubleshooting and still are still having the issue. I started by replacing the bulbs, then replaced the socket and and ground wires in the rear, then I replaced the wires that run the length of the truck (spliced into a foot of remaining wire coming from the firewall in the front, all the way to the rear bumper where it splits to go to the two separate taillights. I feel like the only thing left to really inspect is the wires in the rear bumper and check for a short. I’m going to keep plugging away just wondering if anyone knows of something simple I might be missing or if anyone has seen issues in the junction box on the firewall. Thanks in advance.
CK5
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Help with blinker/brake light issue
- Thread starter Damufuer
- Start date
the turn sigs and brake both go though the turn sig switch. You should check the rear wiring esp if/where any trailer plug additions have been grafted, up to and including the trailer plug socket.
Are all the turn sigs stopping when brakes are applied front and rear ?
Are all the turn sigs stopping when brakes are applied front and rear ?
so I didn’t want to confuse things in my first post because I thought me replacing the main 13foot cable fixed this issue but I just went out to check and it’s back… When I turn either the left or right blinker on, both blinkers in back flash (as if the hazards are on). In the front those blink separately (correctly). When I push the brake all 4 (front and back) stop flashing.
If I can make it even more confusing, that wasn’t always the case as I’ve been troubleshooting. The front at one point did behave correctly, meaning they would continue blinking when I hit the brake even though the back stopped flashing.
Are you proposing there might be something going on with the turn signal switch?
If I can make it even more confusing, that wasn’t always the case as I’ve been troubleshooting. The front at one point did behave correctly, meaning they would continue blinking when I hit the brake even though the back stopped flashing.
Are you proposing there might be something going on with the turn signal switch?
yes that is my suspicion.
Here's what I think might help diagnosis. Go buy a new turn signal switch, but just unplug your old one, under the dash. plug new one in and see if you get normal function. if you do then swap it out in the column. If not plug the old back in and return new one.
Still go over any trailer wiring 9x outta 10 this is a problem
Here's what I think might help diagnosis. Go buy a new turn signal switch, but just unplug your old one, under the dash. plug new one in and see if you get normal function. if you do then swap it out in the column. If not plug the old back in and return new one.
Still go over any trailer wiring 9x outta 10 this is a problem
Do you happen to know the year/model of the alternate turn signal switch harness? I have a 1975 K5 Blazer but I had to replace the steering column with a rebuilt one and that one has a very slightly but different harness. My understanding is for a year or two they switched to a different harness but I tried a bunch of years and couldn’t find it at Napa.
The part number I have is DL6505 but hoping someone knows the alternate one.
The part number I have is DL6505 but hoping someone knows the alternate one.
I posted a diagram of all the wiring here: https://ck5.com/forums/threads/hazards-not-hazarding-when-braking.349803/#post-4356218.
If you look at the turn signal switch, you can see that the rear bulbs are only connected to the brake pedal switch when the turn signal is off (switch centered). Are you saying that the blinker bulbs turn off when you push the brake or they become steady (on, but not flashing)? One way to have all 4 corners do the same thing is have the hazard switch activated, but with a bad or missing hazard flasher.
If you look at the turn signal switch, you can see that the rear bulbs are only connected to the brake pedal switch when the turn signal is off (switch centered). Are you saying that the blinker bulbs turn off when you push the brake or they become steady (on, but not flashing)? One way to have all 4 corners do the same thing is have the hazard switch activated, but with a bad or missing hazard flasher.
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Blinker bulbs become steady when I press the brake.
So I tried a new blinker switch and the issue remains. I looked at the rear and there isn’t any trailer hook ups but all the wires routed in the bumper look pretty disheveled, at this point I feel like the problem has to be there unless it’s in that firewall junction box.
So I tried a new blinker switch and the issue remains. I looked at the rear and there isn’t any trailer hook ups but all the wires routed in the bumper look pretty disheveled, at this point I feel like the problem has to be there unless it’s in that firewall junction box.
If you don't find any wiring mods from the brake pedal switch (as though somebody had problems getting brake lights), I would say someone may have tied the L and R wires together in an attempt at trailer light wiring. Since you would always have one brake light on, that would back-feed all of the others.
Wanted to update everyone, the problem did end up being somewhere in the wiring running in the rear bumper up to the taillights. Rewired everything and it’s working great now. For those that may have a similar issue in the future, I looked up a wiring harness for the rear of the my truck but they were scarce and the few that were out there were outrageously expensive. So what I did was I ordered a wiring harness for a 90’s Chevy truck ($25) and after cutting off the plugs it was nearly identical to what I needed, just had to splice all the wires together. Thanks for all the help and troubleshooting tips!
I'm glad you got this figured out. I was going to suggest checking your blinker fluid level.
