My Ranger, an '04 Edge without cargo lights. The high mount stoplight is faintly lit with the parking/headlights on. I had changed out the incandescent bulb for a LED, and went out to see how everything looked after dark. Well, the high mount had a slight glow to it, not really on, just a faint glow. This was never noticed with the regular bulb. I suspect I may have some stray voltage coming from somewhere, just enough to make the LED glow, but not enough for the normal bulb. When I switched off all the lights, it went out as well.
I tried to find a wiring diagram on line, like I've suggested to others in the past, but no luck from Autozone, or the EBSCO host I've used before. In fact the EBSCO will no longer accept "tech" as a user name or password.
So, anyone got an idea where the problem may lie? I hate it when I can't figure out something like this!!!

 

You are correct, there is a slight stray voltage coming from somewhere that was considered normal and did no harm with the regular bulb. The LED bulb does not present enough load to this small voltage so it glows.

People sometimes have this same trouble when putting LED's in the rear brake lights. Some places it can come from is the cruise control module, or anything tied into the brake signal wire. The only way to find it would be to unplug the different components tied into the brake wire. Your high mount light is tied directly to the pedal switch.

The problem is what to do when you do find the culprit? You probably can't leave the offender unplugged. What I would do is by a load resistor and install it in the light to present the proper load on the circuit, and the glow should go away.

I looked on Autozone's site, and they do have diagrams for the Edge, but they start in the year 2007. I looked elsewhere on the internet, they didn't start making the Edge as far as I can tell until 2006, which I guess would be considered a 2007 model.

 

Hi Dave. I was finally able to pull up a diagram on the Autozone site. I don't know what THAT problem was. It appears, like you said, the brake light switch makes up the regular stoplights, and, the highmount, on two different contacts. Possbly the stray voltage is coming from there. I think I'll disconnect the switch for a minute or three, and check the highmount. That should show me if the switch is the culprit. If that's it, I have a couple load resistors I could put in pretty quickly. The thing that is puzzling me, is why only when I turn the head/parking lights on. From what I see, they aren't connected in anyway with the highmount. So, you don't see a problem with just using the load resistor?
Yes, you are right about the Edge.But, there are two versions of the Edge. The first version was a Ranger until about 2006, when the name was changed to "Sport", and the Edge became a crossover vehicle, not related to the Ranger.
The Ranger "Edge" was a package that included Tbar front suspension, carpet delete, body colour bumpers and valence, and a couple other things, including the highmount stoplight, without the cargolights.

Oh yeah, I should mention I changed out the tail/brake lights for LEDs as well.

 

Ha, just thought of something. I could just leave things alone, and see if anyone else notices the highmount!! Who knows, it might start a trend, and could even meet some interesting people in the process. Wait a minute, meeting some of those "interesting" people may not be a good thing,,,,,,,,,,

 

After thinking about it, I guess it could be a grounding problem at the rear lights. That's the only place I can think of where the voltage could "crossover".

In the rear lights you have dual filament bulbs. Most cars and trucks have the one brighter filament as the brake/turn function, and the other filament as the tail light. Some vehicles, especially newer ones and foreign ones, have a separate orange light in the rear for the turn function, but they still usually use the dual filament bulb for the brake function and the taillight function.

What happens in the older trucks (when they get a corroded socket or corroded ground to the rear lights) is the turnsignal lights in the dash will light up when the running lights or headlights are turned on, because the voltage to the taillights runs back through the rear filament in one or both of the bulbs, tries to go to ground to return to the battery, but finds a high resistance. So instead of going to ground, the voltage runs backwards up the brake/turn circuit and finds a ground through the instrument cluster indicators, lighting them in the process.

I know it sounds strange, but to verify if this is the problem, I would get the 3rd brake light glowing, and then go back and unplug the rear lights(both) and see if it goes away.

 

I follow ya, I'll check that out as soon as it's dark. I'm suspecting the right one. I had used one of those junk quick splices to splice in a load resistor, and thought better of it, and just installed a EP27 flasher instead. Chances may be that I damaged the ground on that light.

 

Well, no glow at all. But, I'm suspecting that ground I may have screwed up. What I'll do, is keep a screwdriver handy, and if/when the light starts glowing again, I'll take the bulb out. I doubt it actually fixed itself! LOL