Newbie here needs some help! When I turn my headlights or marker lights on, my left turn signal comes on and stays on inside the truck and both the front and rear left hand blinker lights are illuminated (not blinking). When I have either the markers or headlights on, I cannot use the left blinker. When all lights are off and I try to use the left blinker, it makes all my dash lights including the clock flicker with it and the whole left taillight flickers as well. The right turn signal works fine no matter what.

I've had this problem since I got the truck. Been trying to investigate the problem but can't seem to find anything messed up. I was thinking it could be the switch so instead of forking over $130ish I got a switch from the junkyard. I wired it up and it did the same stupid thing! Any insight would be greatly appreciated!

 

Sounds like a ground. On the passenger side of cab under carpet the wiring harness goes through the cab on the frame. Check there and make sure the wires aren't skimmed back or broke. This is located directly under the seat on passenger side.

 

Thanks for the reply! I checked it but I don't see any messed up wires as far as I can tell. I unplugged it and then turned the lights on and the lights were normal! So that means that somewhere in the taillight harness from the plug back is the problem correct?

 

Bumping this thread back up. Did some more investigating with the multimeter at the 7-pin tail light connector. When disconnected from the tail light harness, the male end only had significant power from 1 pin. When the male end is connected to the tail light harness I had significant power from 2 pins????!!! Any ideas?! If I'm asking dumb questions it's because I'm electrically stupid!

 

Does your vehicle have one of those converter boxes for the lights??

How do the lights work on the trailer you tow when it is plugged in.

Or is your trailer plug wired up direct to all the different lights

it sounds to me like you have a bad ground in the left tail light housing pull it apart and clean the sockets real good make sure nothing is corroded.

it does not sound like you have any shorts because you never mention any blown fuses .

When checking your plug were all the lights on ?? off?? Do you have any idea how your plug is wired??

Just what kind of voltage readings where you reading when reading at the plug.

Do you have a brake control installed as well??

 

I don't have the converter box for the lights as far as I know. There is no wiring for trailer lights nor a hitch.

Nothing appears to be corroded in the left tail light housing. When I unplug the whole left tail light assembly, it still does the same thing with the exception of the tail light (because it's unplugged).

All the fuses are good.

When checking the tail light harness plug, I had the marker lights on. I unplugged the tail light harness (with the markers still on) and measured the voltage to the plug and was only getting power to 1 pin. When plugged back up to the tail light harness, I got power from 2 pins. I was getting about 12 volts unplugged (from tail light harness) from the 1 pin and plugged up to the tail light harness I was getting roughly 11.25 volts from 2 pins.

There is no brake controller.

 

Have you checked/removed/replaced the bulbs in the rear? I've seen filaments ground out and cause some funny things.

 

Yeah the front blinker had a good bit of corrosion and the rear left tail light had some corrosion but I unplugged both assemblies and turned the lights on and the left turn signal was still on the dash.

 

It is one of the bulbs more then likely grounding back through the turn signal

 

I guess I will check it out again. I just don't understand how this could be the problem even when I unplug both assemblies from the wiring harness. Thanks for the insight!

 

You unplug both rear tail light plugs from the harness.

You are positive this does not have a converter box for a trailer light plug even if the trailer light plug is long gone.

Reading this all again your problem is some place between the left tail junction and the one under the carpet .

Being real careful trace those wires and check both junctions (plugs) for any signs of being corroded or visible damage.

Being a Newbie it is not good practice to go poking holes in wires with test leads.

I can`t remember on these older trucks did the front signal light also do double duty as a parking light also it has been pretty long since I had one.

Good Luck just think how much your learning

 

Well I'm not positive if it has a converter box or not. Where would I find it if it has it? And when I measure the voltage I'm measuring at both sides of the plug; don't worry I'm not poking into any wires. And no, the front signal lights do not double as parking lights. The parking lights are the ones next to the headlights. Yes, it seems as though I'm learning a lot! I guess I will continue the investigation. Thanks for the help!