Running lights and turn signals work not brake lights

[Frattallone]

I have a 2010 4.0 V6 Mustang brake lights were not working few months ago running lights and turn sickles all worked. My wife moved some fuses around all which were good. Touched a couple wires and the brake light started working couple days ago. They just quit working running lights and turn signal lights still work. Replaced the brake light switch check off fuses brake lights still not working at my wits end please somebody help.

 

[86GT351]

Probably water intrusion at the Smart Junction Box. Check the 2 firewall drains. They are known to get clogged and then rain water or car wash water can't drain properly. It ends upo going through the cabin air filter into the vehicle. While in there replace the cabin filter. That gets done from under the hood. The windshield cowls have to come off. It's behind the firewall behind that battery.

 

[Frattallone]

Thank you for the info will be definitely checking it out in the morning!

 

[DieHarder]

What wires were you/wife messing with when the lights worked (where are they located)? Sounds like you have some intermittent/poor connections. If you can repeat the test and note if they start working again that may help.

Do you have a VOM (Volt/Ohm meter) or test light? If not, go get them and consult a manual. This online manual should cover up to 2010 but there may be differences. At least it should get you in the right ballpark. Recommend reading thru the manual first to familiarize yourself with where things are. This online version leaves a lot to be desired but it's free. Likely that you'll need to remove the SJB (Smart Junction Box - passenger side foot well just ahead of the door). Take it out; clean all of the contacts with electrical cleaner and put it back in. Retest for symptoms. Note any changes. If there's corrosion that's likely your problem.

If you have a code reader get the codes and look them up. It'll help you narrow down issues if they're present. If you don't have one you can visit Autozone or another auto parts store and have them test for codes. It's usually free. If you do have DTC's (Diagnosis Trouble Codes) - post them. If not check out some of the links below. They should help.

Ford Workshop Service & Repair Manuals - fordrepair.info Home

Ford Workshop Service & Repair Manuals - fordrepair.info Home

iihs.net

Wiring diagrams - Rear lamps: https://iihs.net/fsm/?d=40&f=Parking, Rear and License Lamps.pdf

Exterior lighting: https://iihs.net/fsm/?d=387

Troubleshooting Tail lights: https://iihs.net/fsm/?d=389&f=Stoplamps.pdf

SJB explained: https://iihs.net/fsm/?d=420&f=Module Controlled Functions.pdf

Removing the SJB: https://iihs.net/fsm/?d=422&f=Smart Junction Box (SJB).pdf