Right rear taillight has constant power to it. Draining battery. What could be wrong?

[markinms]

I'm helping a friend with an electrical issue. The battery discharges and eventually goes dead within 2-3 days.

With engine off and key off, the right rear taillight remains on. If we tap the taillight lense the light will go out, if we tap it again the light will come on. Only does this on the right side.

Question: what would allow a constant power source to the taillight?

Thanks for any feedback!
Mark

 

[cschannuth]

Depending on the generation the right taillight is normally fed from the left taillight so I would find it odd that the right light would be on but the left would not.

 

[tinman_72]

It has to be a short. Your tapping on the lens has narrowed the location down to somewhere around the lens. I would start by removing the taillight assembly and inspect all the wires, especially the plugs. They have a tendency to heat up and melt.

 

[cschannuth]

There should be no hot wire to that tail light unless the lights are on as long as the original wiring harness is unmolested. The wiring harness usually runs down the drivers side so if there’s a hot wire on the passenger side the wire that feeds it from the drivers side would also be hot. Something is not adding up.

 

[markinms]

Thanks for the feedback. I heading over there today with my DVM.

Do you where power to the taillights originates from?

Since no power should be there without the lights being turned on, should I be looking at the light switch?

Thanks!
Mark

 

[Dirtman]

When the truck is on do the lights work? Do they still flicker on and off if you tap the light while the truck is on?

As said there is no power running there unless the headlight switch is on, or the brake light is pressed. So the only possibility I see is the headlight or brake light switch is stuck on and the ground wire is not making good contact but in that case the lights would be stuck on no matter if the truck is on or not.

 

[RonD]

Brake light and 4-way flasher are the only full time power source that run to the tail lights, and they are both controlled by switches in the cab

Now people do wire full time 12v wires to the rear of a truck for canopy lights(or 3rd brake light, but switched)
Also for trailer use

Could be trailer/canopy wiring short to that sides brake/turn bulb wire

Has to be brake/turn bulb, if it was parking light then if would feed power to both sides and license plate bulbs plus front lights, they all share the one wire
And reverse bulb would be white, lol, and that's not mentioned
So has to be brake/turn bulb

And anytime there is an issue at the tail lights on a truck............................its ALWAYS a DIY trailer light wiring issue