Help Troubleshooting High Mount Rear Brake Light 97 Explorer

[edlin02]

Hopefully I am in the correct forum... My Rear High Mount brake light is working intermittently. when I first hit the brake pedal, all 3 brake lights work. I take off the brake and then hit it again, the main brake lights work but the high mount does not. If I continue to press the brake at a close together rate, the high mount remains off while the main brakes are fine. If I 'rest' the brakes for a little bit, all three lights will come on. So... question is... is the fault in the fuse, wire, switch or is it the high mount light itself? As it works occasionally... consistently when rested... I am thinking it is not a wire issue. I had swapped the fuse ... but did not seem to help. I am not sure how it is connected to the brake pedal... what switch/wires I found connected to a switch on the brake seem fine (messed around trying to see if shorting out .. but seemed to have no effect. I am novice and I do not have any decent docs to tell what I was looking at ... any thoughts/help would be appreciated!

 

[rhinodep]

I had this same problem. I read in another thread that the third brake light often becomes inoperative due to dirt and debris in the trailer wiring connectors, of all things. Under one side or the other of the back bumper is a wir
ing connector with a removable cap. Road dirt gets under the cap and causes enough resistance that the ballast in the third light will not operate. Amazingly, I removed that cap, shot some WD-40 in there, and the light has operated without fail since. This fix should probably be a sticky, if it's not.

 

[rhinodep]

I had this same problem. I read in another thread that the third brake light often becomes inoperative due to dirt and debris in the trailer wiring connectors, of all things. Under one side or the other of the back bumper is a wir
ing connector with a removable cap. Road dirt gets under the cap and causes enough resistance that the ballast in the third light will not operate. Amazingly, I removed that cap, shot some WD-40 in there, and the light has operated without fail since. This fix should probably be a sticky, if it's not.

 

[nssj2]

Its most likely the ballast resistor. It's a very common problem with the neon style 3rd brake light. You can either junkyard one, pay $$$ for a OEM, or convert it to a LED setup with this writeup

 

[edlin02]

Thanks for the quick feedback!

Will definitely check out the wiring harness - would be great if it turned out to be that simple!

If still having problems... Hopefully I can test the power getting to the light without too much fuss.... want to isolate the problem to the light unit verses the circuit feeding the light. The ballast resistor does sound like a likely culprit based on the way the light is behaving.

Looks like I know what I'll be doing this weekend...

 

[edlin02]

FIXED!!! High Mount Rear Brake Light 97

Amazing - the Trailer Wiring connection was the culprit!

I noticed some wear on the wires right at the plug. I voltage tested all lines and they were active ... but I could force a short by moving the worn wires. However - even when I made sure there was no short occurring, the Rear Mount Brake Light still operated with the same symptoms ... would light initially and then again only if I waited several seconds. I admit I am major novice here, but my guess is that the overall circuit must have enough voltage loss to cause the issue... but that still does not fully explain the problem.

Anyway - I dropped some solder (poorly) onto the worn areas to seal the wear and improve the voltage flow. I then tested the High Mount Rear Brake and it worked EVERYTIME!!! As I needed this fixed to pass inspection, I kept my temporary repairs and taped the lines well to reduce movement. Secured the harness and retested and still good to go!

I cannot thank you guys enough for your help! As I needed a repair rather quickly and my soldering skills are pretty poor, I was not looking forward to attempting the LED conversion. If I could not resolve by Monday, I was taking to shop where the diagnostic fee was around $100 and if they suggested I replace the light, the list price I had seen was around $350. So with labor, I'd say you just saved me at least $500 (that I did not have)!!!

AWESOME! Thanks again!!!

I do not know how to make this tip/thread a sticky, but I agree it should be!