Rear lights stop working during 3rd brake light change

I had an automotive electrician change out all the regular bulbs in my 2005 KJ Limited to new LEDs. All worked fine and I was very pleased with the results. A new 3rd brake light with LEDs was ordered, along with a flashing module that had various options for the rate and duration of flashing the 3rd brake light. When it finally arrived, I took it back to the electrician for installation.

First thing he did was to remove the old 3rd brake light, then strip a short section of the white wire, which was to be tested to see which of the flash module wires was to be attached to it. Before he could do any testing though, the rear lights all went out. They all previously worked and were less than 2 weeks old at the time.

He checked fuses, removed the LED brake lights and tested them... everything seemed to test okay, but with everything returned to the condition it was in when I first drove in, none of the rear lights were working still.

It was supposed to be a very quick install, so it was late in the day. He was frustrated and I could see that he was not feeling well - turned out he had a bad tooth bothering him. So, I suggested it could wait until Monday and he gave me a ride home while my KJ languishes in his shop for the weekend.

I emailed him a link to the 2005 KJ service manual. I told him I would look around for similar issues, but haven't found any. My hope is that one or more of you might have some ideas what might be causing this problem. Thanks for any help you might offer.

Hey Jim, I really am no expert when it comes to LED replacements. The only LED is a single Led bulb I installed was on the 3rd brake light.
I hope he disconnected the battery before doing all this work, a live short can = a bad BCM day.
Test all the fuses with a VOM to confirm continuity.
As far as this flashing 3rd brake light, maybe try removing that, and use the OEM one and see if that is the problem.
Hopefully someone knows more about resistors issues.
I decided not to mess with LED's as regular bulbs work fine for me.

LibertyTC said:

Hey Jim, I really am no expert when it comes to LED replacements. The only LED is a single Led bulb I installed was on the 3rd brake light.
I hope he disconnected the battery before doing all this work, a live short can = a bad BCM day.
Test all the fuses with a VOM to confirm continuity.
As far as this flashing 3rd brake light, maybe try removing that, and use the OEM one and see if that is the problem.
Hopefully someone knows more about resistors issues.
I decided not to mess with LED's as regular bulbs work fine for me.

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Thanks for the reply. He didn't disconnect the battery this time or any other time that I can remember. I've known and used him for many years. His only job is automotive electrical systems. My only job used to be flooring and I made a few mistakes over the years, so it's possible this is one of his, but I'm sure he knows what he's doing when he opts not to disconnect a battery.

The new LED 3rd brake light was never installed. As I mentioned, all he did was strip a tiny portion of the insulation on the white wire after he unplugged the original 3rd brake light. That was to conduct a test of some sort, which I imagine would only work with the battery connected to the system.

One of the tests he conducted before taking me home was to plug in a regular (non-LED) brake light bulb on the passenger side. It lit when the brake pedal was pressed. Could it be that the KJ just doesn't like LED brake lights?

I wonder if electrical problems are common to the KJ?

Ya chances are the KJ says "No Thanks" and rejects them LOL.
I think resistors have to be added in place with all dual filament bulbs, but what do I know right.
For now see what the tech can figure out, but it sounds like regular bulbs should get you back on z road /working right.

LibertyTC said:

I think resistors have to be added in place with all dual filament bulbs, but what do I know right.

Click to expand...

I think that's only for the turn signals. When he did the previous work, I had purchased resistors with the new LED turn signals.

I do not get myself involved in discussions regarding converting to LEDs as there are too many unknown variables from the LED make to what resistors if any are being used.

I will wait for LED bulbs to start arriving on the motor vehicle scene that are direct screw-in replacements for the incandescent such as we now use in our homes....then I will look into getting some!

Maybe such LED bulbs are available in USA or Europe but none here yet!