2007 T800 Kw tail light back feed

[akwman]

Hello , I have a new used misfit in my fleet . Of course it looks good until you start to nit pick. So last night I turn the truck off , its dark , I walk away ,I see the tail lights have a very small amount of power to them . Every so slight . Of course they are after market round led. But still , it is odd. So should I start at the dash switch or just suspect its gonna be bigger than that after the switch and suspect the Ecm .

[Waterloo]

I would start at the switch, make model of truck would help too...

[Chamberpains]

Not the ecm for sure. It has nothing to do with lighting.

It may be the switch, but I'd lean more towards a ground that is bad or crossed\shorted wires. Check and clean all frame, battery and cab grounds, trace you wires up the frame rail and see if theyre pinched, corroded or melted together Also i had a similar problem a few times and it ended up the trailer electrical cord itself had gotten pinched or the sockets for the trailer electrical cord had corroded and fused together behind the plug. Check the back side of those sockets on the cab and the trailer.

[stevesparts]

I've seen that a lot on a lot of KW's.. mine to.:( it comes and go's. never had a problem with it. cleaned up all the grounds and stuff but it still does it from time to time. it's annoying,but i see it on other KW trucks model's too..

[Rawze]

sounds like a wiring harness or tail light assy getting moisture in it.

Are the lights activated by supplying +12v to them? -- or by connecting ground to them? some vehicles are "apply +12v" for the light to come on, other trucks are "ground out" for the light to come on.

You can usually tell by putting a volt meter to the pigtail and see if you have +12v all the time on the connection that is common to the bulbs.

[Rounded_nut]

My Pete does that too, BUT if you come back in a few minutes they're off, I could be talking out my ass but could be something along the lines of a courtesy light, of course useless, but just the same.

[Waterloo]

I wonder, I had a Pete that went bonkers on my electrically. Spent days trying to figure it out and finally had to take it to a shop. It took them a few hours, but they discovered it was the grounding step from the fifth wheel to the frame. It is a braided stainless steel strap. Somehow it broke at the connection. It was there, but only held together with a few strands of stainless wire. Maybe see if that strap is intact, if you have one.

[mj9770]

My dad has an 07 t800 and so does the neighbour down the road. They both do it. Was told by Kenworth that the load on some led lights is not enough to fully get the relay to shut off, and sudgested to switch to non led tail lights or add a resistor. I think some led tail lights have the resistor built in. Not sure would have to research that.

[Hammerhead]

(11-18-2018 )stevesparts Wrote:  I've seen that a lot on a lot of KW's.. mine to.:( it comes and go's. never had a problem with it. cleaned up all the grounds and stuff but it still does it from time to time. it's annoying,but i see it on other KW trucks model's too..

I've got an '09 T800 that behaves the same way (comes and goes). It's annoying as hell to my OCD!
I can't count the number of Pete and KW's I've seen do this as well over over the years. It must have something to do with a controller somewhere. I personally think it has something to do with the keyless entry/lighting controller. Paccar uses some of the same components (keyless remote fob, interior light delay shut off, etc) as GM, and GM vehicles leave the exterior lights on with that system for a delay to allow you to get out in the dark with lights for "safety feature" that shut off after a couple minutes, this feature isn't used in trucks and I think this may be where the issue is coming from:huh: