Hey guys I really would love some help with this issue if anyone has any ideas at all it's better than where I'm at correctly.


The issue: The drivers side bulb for my 3rd brake light quit working. Sometimes it would come on sometimes it wouldn't. I figured the harness that goes into the headliner was bad considering the rubber plugs that actually go into the third brake light were deteriorating. Before replacing the harness I was able to make the bulb light up by smacking the top of the third brake light which also led me to believe I had a short somewhere in the harness.

- I ordered and installed a brand new ford third brake light harness today only to find out that the same drivers side plug was not working. I took my volt meter to the center (brake) and passenger side plugs and both were hot.

The drivers side plug was not hot. I pulled the headliner back and made sure the harness connector at the back of the cab was hot. It has 3 wires going into it. Only the center wire was hot (black) pictured here...

Theses are the 3 wires going into the plug.




And these are the readings that I pulled from the 3 plugs on the harness. (Note this is the old harness but the brand new harness tested the exact same so I know the short can't be there)


I'm really lost here so any input is appreciated

 

It appears that the plug that is not working is the only one that has the green wire.

 

Did you try a new bulb?

 

yes, I have tried a new bulb and it works perfect In the other two plugs (they're hot) I'm leaning towards the multi function switch on the column? I know this has something to do with the green wire.

 

Maybe your switch has burned inside try to test your switch behind the pedals

 

That wouldn't explain smacking it and it worked.

 

You are right , definitely a bad connection inside your plugs then, the plug and bulb connection not connecting properly

 

Well it connects to the dome light, if I'm not mistaken that's where it grounds, under the dome. That would explain smacking it to work.

 

Winner winner chicken dinner. I've seen those grounds get awfully corroded up there... may be due to a leaky window.

 

Yeah clean it and maybe you are lucky good luck !