I broke my new truck

Juan Cano

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Here is the issue I am trying to solve. When I have the headlights ON, and I use the right turn signal, the dash right turn signal light stays on and the tailight blinker doesn't flash (it might be ON, hard to tell). The turn signal control goes back to the middle but the dash light/taillight issue persists for several minutes.

Turn signals work fine when headlights are OFF.

• All the tailights bulbs are LED
• All are NEW bulbs I just installed yesterday
• I swapped the Flasher with a new one but it didn't make a difference.

a) The headlight power (brown wire) is somehow causing the right blinker (green wire)to stay on. How is this? Short somewhere? All wires seem fine. Need to test
b) I need a special LED flasher. But I don't think this would fix it as the turn signals work fine when lights are OFF
c) Don't drive at night
 

Ellie Niner

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Here is the issue I am trying to solve. When I have the headlights ON, and I use the right turn signal, the dash right turn signal light stays on and the tailight blinker doesn't flash (it might be ON, hard to tell).

Turn signals work fine when headlights are OFF.

a) The headlight power (brown wire) is somehow causing the right blinker (green wire)to stay on. How is this? Short somewhere? All wires seem fine. Need to test
7776

Okay, I don't want to get to deep here, so will say that it will be easiest to just bin the LED's and go back to incandescent bulbs. Here's why:

The front side markers are wired so that they ground through the front turn signal, so that they'll do double duty and flash with the turn signals. The hot/ground polarity switches back and forth when the headlights are on, and some LED's don't like this (incandescent bulbs don't care). If one of your turn signal sockets loses its ground, or the front turn signal filament burns out, the side marker will try to find its ground through the dash indicator, which lights it up. When you're using semiconductors (LED's) in a circuit like this, all bets are off, and strange things can happen. Some LED's will work with either polarity, but others won't. It does concern me that you can't tell whether your right blinker is flashing or not... some of the LED stuff I've run into doesn't have enough of a bright/dim ratio to work safely.
 
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Juan Cano

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@Ellie Niner I was starting to think that. It all seemed to work before I had to replace all the horn and blinker wires inside the steering. I was also considering a special LED Flasher; I read that those work with both LEDs and regulars. Or swap to regular bulbs seems worth a try.

Thank you for the advice, it's great.
 

Bextreme04

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When you have blinker issues only when the headlight is on, it means you have a broken ground in a bulb holder on that side. It is super common and I have had this issue on both squares I've owned. You can try to just wiggle or pull on the ground connector on the back of the bulb holder while the turn signal and headlight is on. If the issue goes away when wiggling a certain one or if the ground pulls out of the connector you have found the issue.
 

Juan Cano

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@Bextreme04 Yes, I was going to check that. Raining today and truck is outside. Thank you for the tip.

BTW, random question. This is an 86 C10. Water gets into it by the doors it seems. It has the weather stripping around the cab. Is there also supposed to be weatherstripping on the actual door at the top? Or is that only in the older models?
 

Bextreme04

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@Bextreme04 Yes, I was going to check that. Raining today and truck is outside. Thank you for the tip.

BTW, random question. This is an 86 C10. Water gets into it by the doors it seems. It has the weather stripping around the cab. Is there also supposed to be weatherstripping on the actual door at the top? Or is that only in the older models?
There were certain models that had the extra strip on the door itself at the top. My 1980 K25 has it on the top of the door as well as the regular weather strip around the cab door opening. Water that is getting into the truck from anywhere else will eventually make its way to the door area though, so make sure that it isn't dripping down from common cab leakage areas like the cowl area, bottom of the window seal, or non-sealed drip rail screws.
 

Ellie Niner

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You *may* be able to get by with just changing front side markers back to incan.
 

Juan Cano

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Does not seem to be a ground issue. I cut off the light socket in question and used a test light and still see the issue. Perhaps somewhere in the rear harness the wire for the light (brown) and the wire for the blinker/brake (green) are touching?

BTW, the rear light harness is grounded at a single spot, the body by the left tail light. In the original wiring diagram it shows it grounding in two places, one for each side. Not sure if that matters much.

The turn signal starts working fine; then it's erratic; then sometimes blinks slowly, like half speed, and then it ends up staying on. The left turn signal continues to work fine. I have changed the Flasher Relay to see if that matters and it doesn't.

I guess I should just go find some incandescent bulbs for this and see what happens. Or take the rear wire harness down and visually find any corrosion.
 

Juan Cano

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OK!! So I swapped the brake/blinker LED for an incandescent one, and that fixed. Sonnnnofagun!

Prior to that, because I am hard-headed, I removed the tail light harness to check for any shorts. I redid some connections that looked just old and rusty and added a ground wire to the passenger side of the harness since it didn't have one. But that didn't fix the issue with the LED light. But the old filament bulb did. Thanks @Ellie Niner !

The sockets are brand new, I swapped them. And no ground issues. So maybe it's just that the power from the headlight oozes into the blinker and since the LED is so sensitive it freezes up. I think someone mentioned that.

Anyway, that is fixed. Now to figure out why my electric windows work sometimes and sometimes don't. But perhaps I should drive this truck for a few weeks and enjoy it!!!!

Thanks all!
 

DoubleDingo

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Glad you got it fixed and posted what you did to fix it.
 

DoubleDingo

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The issues you had is why I will stick with incandescent bulbs. They don't burn out often, and there isn't any fiddling with them, unless of course a bad ground is present.
 

Ellie Niner

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The issues you had is why I will stick with incandescent bulbs. They don't burn out often, and there isn't any fiddling with them, unless of course a bad ground is present.
I'll second this. Plus, you are assured of them being 100% compatible with the optics of whatever lamp you install them in. For example, I can see the front and rear turn signals on my truck reflecting off of signs FAR away.
 

Juan Cano

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LOL. I think I need to work on my testing. Yesterday I take the truck out for a drive at night, turn the lights on and notice the right turn signal on the dashboard stays on all the time while driving!! WTF! But the actual blinkers work fine. So right dash light is on, but if I turn right, it blinks fine and the tailight blink fine and the side and front markers blink. When I complete the turn, the dash light stays lit. And the left signal works just fine. Just the right dash turn signs stays on when the lights are on.

I really thought I checked it thoroughly.

I should add that about 1.5 months ago when I took the dash off (I can't even remember why), I decided to swap out of the light bulbs on the dash board with........ LEDS!!!!! Or course!

So maybe when I turn the lights on, which turns the dash lights on, the right blinker dash light is too sensitive and it turns on? Worst is that damn LED is so freaking bright!!

Sigh. I don't think I'll fix this for a while. I understand the gauge bezel would have to be removed to swap bulbs and it took me hours to put it all back together. Don't really feel like doing it.
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Ellie Niner

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That's usually a sign of a bad ground or burned out filament on the front signal with incandescent bulbs; w/LED, I donno. Try removing your right front park/turn bulb, and the green indicator should go out. If you haven't installed an incandescent bulb in the RF park light, give that a try, at least for testing purposes.
 

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