This is revisiting a problem I had last spring and it just started again last friday. If I push in the brake pedal, the amber and red taillights light up and the license plate lights and the turn indicators on the dash glow too. Now if I turn on either turn signal when this is going on, it blinks rapidly as if a bulb was out. If I let off of the brake, everything is fine and dandy but as soon as that brake is pressed, the back of my truck looks like twinkling christmas lights. It isn't constant though which really bugs me. Since Friday, I can drive from one stoplight to another with no problems. Then next thing I know as I come up to another one, or needing to turn, the lights are freaking out. Then after another couple of stoplights later, back to normal. I'm guessing that it has to be something between the brakelight relay and the rear? I hate this electrical stuff.

 

i would see if u can get someone to put foot on break and start moving things tell u get it to happen or stop and then u know where to look, when it happen last time what made it stop or did it stop on its own?

 

i ain't gonna lie. your rig is messed up. my diagnosis: electrical turrets


you might try taking out the flasher switch. turn signals shouldn't work, but everything else should work fine. also, make sure there are no stray wires or bad connections behind the tail lights

 

Well last time it hapened it was doing it constant and the guy I bought it from had a trailer harness that was very badly wired in. I just went through and cleaned all that up and cut the trailer harness out. Hadn't had any problems since until now.

 

sounds like they might be touching again, take off the tail lights and look at wiring, trace the harness all the way back to where it all connected to the truck harness,

 

I'm going to pull the truck in the shop here at work after 5 to start checking stuff out. I printed off a wiring diagram and I'm wondering, could the relay switch behind the brake pedal be going bad? What do you think?

 

It sounds like a bad ground. If the lights are not grounded they will back feed into your other lights to find a ground. I would start there, the grounds at the lights that is.

 

That's what I was thinking to cobolt. I'll get into it here later on hopefully and update with what I find out. Wondering if I have a stray wire or two from the old harness thats still hanging out somewhere.

 

Ok, so far I've got both tail lights out and reconnected on a box under the truck so I can see them while I'm underneath. Brake pedal is being held down by a 2 x 4 and both red and amber lights are on plus turn signals and amber by headlights but everything about half bright. So, somewhere I must be connecting the full circuit to all the lights right? Funny thing is if I tap on the back passenger side light housing then that side goes out except that the drivers side stays red, no amber. (if that made any sense). Then tap again and everything comes back on. So I disconnected the pass tail light but no change in drivers. (I hope there isn't too much rambling where it's hard to understand)
That's where I'm at right now.

 

take all the bulbs out but the brakes. see if they go out or get brighter. if they go out, you are missing grounds.
As you can see I don't have many posts, so I have not played with these trucks much, but I have played with alot of lighting. Older trucks had a single ground point to the truck bed or frame, or were grounded close to the lights them selves. It sounds like there is one ground and it is not there...

 

... you can try getting a tester wire (2 feet will do) and touch one to the frame, a bolt or latch and the other to the socket. of it clears up, you know it is a ground, chase it and reground

 

so took out the bulbs minus the brake and the brake bulbs went alot fainter than before.

 

To me, that says it is a bad/almost no ground, try the test wire. Then trace it to the ground wire and move it from the really rusted spot.

 

Well so far in this adventure all I know is that every thing freaks out ONLY when either the brake pedal is depressed or the clearance lights are turned on. As for grounds, have know idea where to even start. I have found maybe 3 that have a ground (white/black) and I checked them, tightened down if needed and still nothing.

 

don't forget that some of toyota wiring is switched ground. look in the back of the haynes manual and follow each trace. or at least that's what i would do...

 

Here we go:
So since I left the truck here overnight I got my boss in on this project. We got out the testers and started at the tail lights. Eventually we found that there was no polarity between the inside of the bulb housing and the outside because with being original, all the housings are rusted thick. We filed of a small spot of rust and !tadah! we were getting polarity. So ,if I feel like it, we thought about cleaning up all the housings from their rust blankets and then relocating the ground wire to a new spot. I think it'll just be easier to check some new lights out at the pull-and-save. Mine our kind of crappy anyways. Then for some reason we put a test light into the ground connecter of one of the harnesses and we got a faint glow through the ground wire????? I took out one of the bulbs from the other side, put it back in and everything is fine now and works perfect. Here I was looking for these grounding points and never even thought about the ones on the bulb housings. We'll see what happens on the drive home. If it happens again, I'll try new bulbs first then if that doesn't work some new tail lights.

 

Oh and irab88, you're right about the haynes. The chilton I have has really good diagrams but atleast haynes tells you where the grounding points are located. Thanks for that info.

 

So last night the lights only worked for about 6 blocks then back to wacko. Spent 2 hrs this morning going over the same stuff as yesterday and then had a major duh moment. I just spliced in a new wire with the ground wire under the bed and ground off a spot on the frame, ran in a self tapping screw and now everything is working as it should be.

 

hooray for troubleshooting! glad you got it fixed!

i had a similar moment when i went to start the truck after replacing the fuel pump bracket. i learned that it's hard to start a motor with the fuel pump un-plugged

 

this happens a lot with older trucks and the rigs you play in i would recomend putting silicone on youre grounding points and on the back side of the light housing to keep water out also toyota used a rubber ring that runs around the whole light cover check those and see if you cant get them to stay in there properly. this is just a suggestion to potentially keep this from happening