interior dome lights
 

So have been messing with my interior dome lights among other things. Today, I went around checking everything and tried again. LIghts do not turn on with doors but this time they would turn on very dimly when I turned them manually which had not worked previously. Now these are new LED bulbs so they should be bright. Any ideas where to look now? I am checking the charge on the battery but I figure if they turn on dimly manually then they should turn on dimly when door is open. I don't think the battery is low either.

Well I charged up the battery and still same result. Dim lights when manually turned on but nothing with the doors. Any ideas?

Manual on uses +12 volt from fuse 20 inside truck. Maybe your ground is bad at the light assembly.

Of they're LED somwtimes flipping them around helps..

LED lights only light when connected up with the correct polarity. Otherwise they don't light at all.

If they're dim, they're not getting enough voltage or not correct for the application. Check the voltage across the LEDs with a voltmeter when they're on. Or you could just put one of the original lamps back in and try it that way. If you've got 12V across the LED or if the original lamp works correctly, you've got bad or incorrect LEDs.

The MFU controls the interior lighting on the D1, but I can't seem to trace it out on the D2 diagram.

My guess is you've got a bad 12V source, ether corrosion on a fuse or a blown fuse. It's unlikely that the lamp switch ground and the electronic module that turns on the lights from the door switches are both bad.

Take a look at these two pages from the electrical library. The dome lights get + power on the color wires, and ground on the black wire, but blacks run back in harness to these headers with frame ground point. That bolt at each header.

If fuses bad, yep, no lights.

But, if ground is open or high resistance, fuse can be good, 12 volts can be read at bulb socket to a different ground point, but enough series current will not flow to make bulb glow or excite the LEDs. The LEDs glow dimly as they are getting very low current flow, and it may even be through other devices connected to same ground header (back feed). If ground were high resistance (corrosion) a digital meter might still read 12 volts acoss and open lamp socket, because that style of meter uses even less current than the LED. The real test is can you read 12 volts across a good load, like the original bulb, etc.

When guys go mucking about in the hidden spaces, like head liner, some times wires run to spots you would not imagine. Like the ground for the D2 fuel pump runs to the engine compartment. The circuits manual and electrical library are you best friend.

Might just have to snug up the header "fixings".

dome lights
 

Thank you guys. I will try one of the old lights and then check the grounds. Savannah, thanks for the pages. Will let you know what I find. May be late tonight or tomorrow before I can look at it.

volts
 

Well I have about 8 volts at the light. Light also was brightr tonight but not constant, it would get brighter and then dimmer flickering back and forth. Still nothing with the doors open. Only works on manual. Will try to see if I can find the headers in the document you sent tomorrow night. Oh, I tried the regular bulb I took out and it either is blown or else not enough coming through to light it up.

You have high resistance (corrosion) in the circuit. Now that could be on the battery side (like a hair line crack in a fuse or a bad fuse block), or that ground header, or a wire somewhere. You could isolate this a little, run a jumper from the black wire at the light to a different ground. If light works, then problem is the old ground side.

If there's only 8 volts with a low current LED, then there probably isn't enough there to light a regular lamp.