98 xlt no brake lights/3rd light blinking

[BillM]

I noticed in the dark tonight while walking up my driveway that the 3'rd brake light was blinking faintly. When I step on the brakes with the headlights OFF the two brake lights work and the third does nothing. Then, when I turn the headlights ON and step on the brakes the third light works,but the lower ones dont. Does anyone have a idea on what the problem could be? I can't drive it at night until I figure this out. My only other vehicle is a 78vw bus with no heat!!! Please help!!

BillM
Mystic,CT

 

[SGR1600]

Have you done any wiring work recently? Sounds like crossed wires somewhere...

 

[BillM]

Have not touched a thing ever. I hope it starts this morning. I am going to check all the bulbs and see if one is bad/shorted causing this problem. I just cant imagine how much I would get soaked to have this repaired.

Bill
Mystic,CT

 

[BillM]

I now have only just a third brake light. The two lower don't work. Tried bulbs,
new brake switch on brake pedal,and checked all fuses. Still need help.
Anyone got any ideas???

Bill

 

[Opera House]

Often when you get an interaction between headlights and brake lights it is a missing ground for the brake lights. Does your vehicle have the lamp warning module that checks lamp current for bad lamps?

 

[BillM]

No, it doesn't have the bulb out indicator.
I had to pull a fuse in order to get the
third light from blinking faintly. I wonder if the factory alarm has something to do with it?(I think it's factory or at least a dealer add on. I was able to order a replacement remote from the local ford dealer). The Haynes manual wiring diagrms do not come close to whats in my 98 XLT. Needing this vehicle ASAP I scheduled an appointment for tomorrow.
Hopefully,I can figure it out before then.
Bill M < how I'll look after the dealer sticks me!!!

 

[BillM]

I finally fixed my rear brake lights. Both rear bulbs were blown. I had used a bulb in the garage to test and a meter. The spare bulb I had was no good. The meter showed a light short in the bullb which I assumed was the filament being normal.
I made an appointment for the x at the dealer for Wed. I decided that I would install two new bulbs just to make sure.
Installed the new bulbs and everything is fixed. The third light no longer blinks and all the brake lights work. I am not really sure how the third brake light works,but
it must be a voltage or resistance sensing
light of some kind. Thanks for all the suggestions.

Bill M