Need ideas for diagnosing rear brake light issue

FIXED IT! I went back and checked the MF switch. I still have the old one so I was going to swap them and test it out. As I was pulling out the MF switch I noticed the top wire clip was not fully seated. Hooked up the old MFC switch and the brake lights worked. So reinstalled the new MFC and fully seated the clip and now have working brake lights.

Seems like when there is any issue with the lights the culprit always seems to be the multi-function switch. Very happy to have found the issue...I hate electrical stuff and was dreading tracing wires.
 
  • Like
Reactions: Tony P, machoheadgames and rasband
I had this problem the issue was the plug on the multifunction switch. Check there all of the wiring goes through there, then check the wire route from the passenger side under hood fusebox, a wire might be broken in the loom.
 
SoCalTJ said:
Just thought of something else. A few weeks ago I replaced the multi function switch because the turn signal lever was broken. But that doesn’t have anything to do with brake lights does it???
Click to expand...
The brake light power wires have to pass through the multifunction switch so that the multifunction switch can properly cancel them for the turn signals. You might need another MFS.

edit: I see now it was solved by this very solution. Good to hear. Anytime you have some working rear light functions but not all, it’s usually guaranteed to be the MFS not handling all the functions correctly anymore, or in your case a physical connection issue.usually not a wiring or ground issue because the wires and grounds have already proved to get the power where it needs to go since the other functions (hazards, turn signal, etc) work. So that really only leaves the switch.
 
SoCalTJ said:
I tried searching some older threads but couldn't seem to find much. My rear brake lights are not working. Heres where Im at:
  • blinkers work
  • running lights work
  • hazard lights work
  • checked fuse behind glove box...even switched it with another one
  • tested the brake light switch on pedal and its ok, I also bought a new one just in case and that didn't do it
Whats next?? What should I try?
Click to expand...
Your taillights are grounded through the tub. I had a similar issue. I took the male and female ends off the taillights cleaned them real good with electrical cleaner and that fixed the issue. Hope this helps
 
Top Bottom