Brake lights come on with ignition

[88xltranger]

Hopefully I'm just overlooking something simple but with key off and lights on, the park and brake lights operate normally. As soon as the key is switched on with the park lights on they brighten up like I'm pressing the brakes. Using the hazards or turn signals with cause them to go back to the park setting but when turned off they go back to being bright. With key off they operate completely normal.

Probably worth mentioning all of my lights are LED now and I have swapped out the standard flasher relay for an LED compatible one. Any ideas?

 

[RobbieD]

It sounds like you didn't have the problem with the original (style) incandescent bulbs and flasher, right?

Can't rule it out, but let's assume that the replacement LED lights and new flasher are not themselves defective, causing the problem.

If so, it sounds like you may have a problem in your truck's wiring harnesses, and it's likely a bad ground. An EVTM (wiring manual) would be the best help for you. Otherwise, you have to just go over all of the wiring harnesses, looking for disconnected, missing or rotted wires and terminals, especially grounds. Check the terminals in all of the light sockets, too, for damage or rot (green crap). Anything in the wiring that's been hacked, repaired or "improved" in the last 32 years needs to be looked at, too.

From your description, the LED lighting is finding a ground path through unpowered circuits; once the key is on that ground path is blocked, and the lighting circuits are crossfeeding trying to complete their own circuit to ground. Since LEDs don't require the power or grounding that the incandescents need, a wiring issue shows up with the LEDs and not the original parts.

It might help isolate the problem by putting back the original parts, on step at a time, to see if and at what point the problem goes away.

Just an observation, but the weirder the problem, the more likely it's ground related. Good luck!

 

[88xltranger]

It very well could be a ground. I havent checked anything because it was late and I've been making "improvements" in other areas of the truck. I dont remember it having this problem with the incandescent bulbs but I cant say I have driven much to notice, and havent driven it at night at all yet. I do know it had some wiring issue at the back when my brother owned the truck but thats been a few years now.

I've been in the process of modernizing all the electronics and wiring I can but I started at the front and was going to work towards the back. Guess it wouldnt be a bad idea to go ahead and do the back. On that note, does anyone know where I can get factory style bulb sockets?

 

[RobbieD]

If it were me I'd start at the back and work forward. Trucks in general seem to get their rear harnesses beat on; things like trailer harness adds, maybe just more exposed in general?

Replacement light sockets should be easy to find, even like at parts stores.

Curious what you find, when you get it sorted out. Good luck!