2010 KW T660 visor lights stay on with key off

[Chamberpains]

After sitting in the rain for 5 days my visor lights have decided to turn themselves on without the switch. I've pulled and checked all fuses, breakers and relays. They all are fine and to my surprise do not shut the visor lights off when all of them are removed.

The only way i got the lights to shut off is to disconnect the batteries. They stay off until i turn the key on. Then they come on and stay on. So my next move is check the light control module. If I ever find it.

Does anyone have any idea where this module is located on the truck?

[Chamberpains]

More information. I spent the morning in the dark pulling fuses and relays 1 by 1 to see what circuit will kill the visor lights. Not a single one did anything. The only thing that will make them go out is to unhook the batteries. They stay out then. Once the key is turned back on though, they don't immediately come on but they do precisely when the fuel primer pump kicks on. Then they stay on.

What cab module turns on exactly when the primer pump kicks on and where is it located on the truck? Its about 2 full seconds after the key is on.

Another thing I just found was after the batteries are unhooked and visor lights go out, they work just fine by switch when the batteries are hooked back up. Heres a strange thing though, the cab overhead interior lights and the bunk alarm and clock go on and off with the cab visor switch until, once again, the key switch is turned on. Then everything energizes normally. The interior lights and bunk clock all function on their own once again. But the visor lights are stuck on then.

[Chamberpains]

I found the lighting module. It is located behind the HVAC dash panel. Its accessible through there or down from behind the main switch panel. I unplugged it completely and the visor lights don't respond. They stay on. All the other circuits in the module do shut off i believe. Turn signals and head light did not work with it unplugged.

So im stuck. I'll be chasing down the wires from the visor lights next to see if the they junction with something else. Im fairly certain im not chasing a random circuit cross feeding voltage because of the fact that the visor lights go out and stay out when the batteries are disconnected and reconnected but will come back on and stay on when the key is cycled on for a second or 2.

Onward....

[Chamberpains]

Found the culprit. Behind the left side guage cluster panel is a harness labeled (IP) to instrument panel harn. It combines the visor lights and some of the instrument cluster feeds. It has green cheese throughout the plug. I'll be spendinv the day pulling pins and cleaning them. Then resealing.

This makes sense that the instrument cluster takes a second or 2 to key on through the CECU. This is why my problem had this exact timing and is combined with the visor lights coming on. All these wires run into this plug.
   
   

[Rawze]

thanks for sharing all this info with us and pics.

the next thing now is to find out why it got that way, especially since it is in the inside of the vehicle where it should NOT be getting wet.