PDC Fuse #23 Short

showes · 08-14-2012, 12:13 PM

2000 Cherokee LTD 4.0

My brake lights haven't been working (none of the 3). Found blown Fuse #23 in the Power Distribution Center under the hood. Replaced fuse and it immediately blew again. I must have a short somewhere in the brake light wiring. My question is - where would I even begin to look? I checked all 3 brake light sockets (wiring coming out) and they look OK. I took the rear compartment side trim off (behind the spare tire) and found 3 ground wires that are all securly fastened to the body.

No electrical work has been done within last 5 years and no mechanical work has been done for last year or so. Just noticed brake lights weren't working about 2 weeks ago.

Any ideas on most common causes?

crzmn1 · 08-14-2012, 02:27 PM

check the brake light switch to see if the wires are shorting

showes · 08-14-2012, 02:32 PM

Thank you.

I replaced the actual brake light switch a couple of days ago. I have cruise control and when I set the cruise and tap the brake, cruise goes off. So, I'm assuming the brake light switch (which also controls the cruise-off) is working correctly. However, maybe I'm wrong. Could the brake light switch wiring have a short that is only impacting the brake lights and not the cruise-off feature?

crzmn1 · 08-14-2012, 03:49 PM

i am not sure, but it is possible that the switch has a separate wire for the cruise and brake did you check the fuses under the dash?

showes · 08-15-2012, 09:26 AM

Thank you.

Yes, all fuses in the passenger side kick panel are good. Only the PDC fuse #23 is being blown.

**ChristopherJ** · 08-17-2012, 08:11 AM

I have the same exact problem with a different cause it seems. No brake lights but all others work just fine.

The bulb lights up when the headlights are on which tells me it isn't wiring. The filaments are intact. The fuses underneath the kick plate in the passenger floorboard are working properly (even #23 is intact). I do not get a click when pressing the brake pedal so I'm guessing it's my brake switch relay.

showes · 08-17-2012, 08:21 AM

Thank you.

A few comments --

1. My tailights (when the headlights are on) also worked correctly. I've checked the bulb double-filaments and they also look fine. I actually replaced the bulbs just to be sure.
2. I don't know for sure, but I think there still could be a "wiring issue" as the tailight wiring and brake light wiring are separate from each other. Just because there's only one bulb for both, I'm pretty sure there isn't one wire for both.
3. My passenger-side kick panel fuses are also all good. The #23 fuse I was referring to, that is blowing each time I replace it, is under the hood in the Power Distribution Center located close to the battery.
4. My brake pedal brake light switch doesn't ever "click". I don't think you can consider a click or non-click as a sign that it is or isn't working. I had a brake light problem about 5 years ago and replaced the brake light switch. It fixed it immediately. It's easy to replace and you can buy the after-market switch at Auto Zone for about $13.

JWELK · 08-17-2012, 09:07 AM

I had a defective cruise control, caused the same problem. It blew the brake light fuse.

showes · 08-17-2012, 09:27 AM

Thank you. Very interesting. Can you elaborate?

I know the brake light switch on the pedal controls both the brake lights and the cruise control disengage. I understand how they are connected.

I tested my cruise a few days ago and it's working correctly. I can set it and then press the brake pedal to disengage it. Works every time.

Was your cruise not working correctly, is that how you knew it was defective? Or was it working correctly but you figured out it was somehow defective and was impacting your brake lights?

showes · 08-18-2012, 04:51 PM

I know there are people out there who really understand wiring and electrical issues. I need your help.

I replaced the underhood Power Distribution Center fues #23 with a new 15amp fuse. Then I started my Jeep (without touching the brake pedal). I checked the fuse and it was still good. Then I turned the headlights / tailights on and checked the fuse again and it was still good. Then I used both the left and right turn signals and checked the fuse again, still good. Finally, I hit the brake pedal. All 3 brake lights lit up for about 1 second and then went out. I checked the fuse and it was blown.

I repeated the above procedure and the results were exactly the same.

In my initial post I mentioned that I had pulled the driver-side rear compartment panel and visually inspected the 3 ground wires that come off the wiring harness and attach to the metal frame. They were all solidly attached and, visually, I didn't see any wire, wiring harness, or wiring harness connector integrity issues.

Why is my fuse blowing when I engage the brake lights?

**ChristopherJ** · 08-20-2012, 02:35 PM

If you have a multi-meter and a wiring diagram, you should be able to localize where the problem is occurring by taking measurements across each length of wire. Your fuse is blowing because of too much current obviously. You've shown that it isn't the relay, a bulb or a fuse in the cab. I would look at the wires coming and going from the fuse box in the engine bay for as long as you can follow them. I'm curious if you might have a frayed wire touching the body somewhere. I'm not sure exactly what that particular fuse you're blowing controls but it seems like it would do more than just brake lights and you'd have other electrical symptoms.

Disclaimer: I'm not an electrician, just a know-it-all