Brake lights aren’t working

[01gtstang92]

So I have a 01 mustang gt. The brake lights on the corners won’t work. The 3rd brake light is. I have power coming out of the switch. My running lights work. My blinkers work but not my two corner brake lights. Has anybody had this problem? If so what’s the fix?

 

[wmburns]

This is frequently a problem in the multi-function switch. Do the hazards light work? Try exercising the hazard lights switch on/off a bunch of times. Does this change anything?

 

[01gtstang92]

This is frequently a problem in the multi-function switch. Do the hazards light work? Try exercising the hazard lights switch on/off a bunch of times. Does this change anything?

The hazards do work except for the front right one because it doesn’t have power for some odd reason. I’ve pushed the switch several times to make sure it’s not stuck and canceling out some other stuff. Idk how to track down shorts I’ve looked at the wiring under the dash and the trunk and it all looked good. I haven’t been in between because i don’t wanna tear my car apart like that. Like I said I think the shirt was with my radio because when I first got the car if I left the radio fuse in it would kill the battery over night. So I just pulled the radio fuse. Besides that I just have a normal test light I don’t think it can load anything

 

[wmburns]

Besides that I just have a normal test light I don’t think it can load anything

If the test light is listed as "computer safe" it's likely too low to test lighting circuits. What you want is an old school "incandescent" style that draws more than the tiny amount that a "computer safe" unit will draw.

Note, for go/no go testing even a computer safe test light can give some useful information.

Just checking. Are you sure the correct bulbs were used?

Have you check the bulb sockets for evidence of water, corrosion, or over heating?

Have you measured and confirmed the voltages and grounds inside the bulb socket? Likely this will tell you a lot.

EDIT: Finally. You are aware that for the 1999-2004 model year Mustang there are TWO dual filament brake light bulbs per side right? One of the light bulb sockets only holds a single filament exterior running light.