04 cummins brake lights started flickering today but are now staying on when truck is off.. heard clicking from fuse box but couldnt figure out where it was coming from...fuse box diagram has no brake light relay...
replaced the switch and everything worked properly till last night when looked out at truck and saw that the brake lights were back on....anyone ever dealt with this problem or where to start?

 

brake light switch needs adjusting...... follow the brake pedal /arm up to the pivot point and you will find it , the switch also turns off the cruise control when you step on the brakes......your cc probably doesn't work.... if it does, you may need a new switch

 

I agree. It's probably the brake switch. I don't think they are adjustable though. Once it is released against the brake arm it's THERE! You can get them (at least for an 01) the the local auto parts store. I got one at O'reilly, for like $15.

You can get to it much easier if you remove the molding below the steering column. Otherwise you need to be a contortionist monkey that functions well upside down!!!

 

Thanks guys. Its my buddies truck and this all started when we were leaving the zone we were snowmobiling at yesterday. I will pass the word to him.
Thanks again

 

Some of them are adjustable. You pull the plunger out, which resets it, and when you reinstall the switch, and the pedal returns, it sets the plunger at the correct depth. That's how it works on my 94, anyways.
After replacing my brake booster, the brake lights were staying on. Before realizing that the plunger could be reset, I wallowed the screw holes out so that I could adjust the switch.

 

It's a plastic switch with a couple of tabs on one end that are made to fit in the metal slot to hold the switch in place. You insert the tabs and rotate the entire switch about 30 deg. and that's it.

On mine there were instructions making sure you did not release the pin until the switch was in place, or the switch would not function properly.

I think most guys who drive big trucks either have big egos or big bodies! When the big body comes with big feet, and one of those big boots connects with that plastic switch----the switch loses.

 

Either your switch is bad or, if the truck has a lot of miles, the return spring is getting weak and not returning the pedal all the way up. I've fixed this problem on vehicles from the 1948 model year up. (No, it didn't work on a '48 when it was new.) It has always been either the switch or spring.

 

well i replaced the switch this morning and everything seemed like it was working properly till tonight when i looked out at the truck and the brake lights were on again.. Anyone have any other ideas?

 

If you lift up on the brake peddle do the lights go out? If so then you either have pedal droop or the sw is incorrectly adjusted.

Also unlikely but if your trailer plug is some how shorting the +12v (for charging the trailer battery) to the brake lights.