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Weak tail lights

Goose

Goose

1/2 ton status
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Feb 17, 2000
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Location
South Central Kansas
My new '86 has some lighting probs.
The turn signals to the rear are really weak, they just barely light up.
The brake lights don't work either.

Funny thing is if I have my left turn signal on and step on the brake the signal stops blinking!

I have fixed some of the old splices where the PO used the clamp on slice thingys that always corrode. I've also checked the wiring around the steering column. I dropped it down and looked for frayed or broken wires.

I'm obviously getting some wires crossed between the brake and left turn signal. Anywhere else I could check?? Anybody with a similar prob???

thanks in advance
 
didnt notice if the 86 is a truck or not, but I had problems on mine w/ the lights after I had a line-x liner sprayed in. Screwed up the grounding of the bed to the frame, run a groundstrap from the bed to the frame, they work like a charm again.
 
Might wanna take a peek at the main wiring running along the frame.. iirc, it's a green, yellow, white and brown bundle... They like to chafe thru where they use slide-on clips to hold it to the frame... check your grounds in the light buckets in the back too....
 
The PO added some ground to the frame from the bed. Sounds like he had the same problem. I'll double check his work and check for chaffing.

One area I couldn't check was above the driver side fuel tank.
I'm in the process of removing the tank shield and tank.
What a mess! Mud is packed around the tank, and I smell fuel.
I'm prolly gonna have a leaky tank.

Fun, fun, fun
anyway, thanks for the advice
 
Update:
Got the driver side tank shield off. It was holding about 40 pounds of mud, sand, and straw against the tank. It would make some real nice adobe.
Anyway, found a dent in the front of the tank and a good deal of surface rust on it. Still smelled like gas, so I think I know what that means.

Now I need to drain it and drop it so I can access the wiring above it.
Anybody want to help getting covered in mud and gasoline????
 
Wireing takes pacitence to trouble shoot so just start at one end and move in one direction [dont' jump all over]. One problem I had with a truck was the trailer wireing the PO had no idea what they were doing and that had the results you are describing. It's something easy to check out anyway.


chris
 
O-yea I know this sounds stupid but I've seen people put the bulbs in backwards. the 1157 bulb that runs both brakes/tail/turn siginal have offset nipples that if forced will go in and run the lights dimmley and when you turn on the siginal you can't see the brake. Or the tail lights look as bright as brake lights. Like I said this sounds stupid but I've seen it.

chris
 
Update

Maybe I have been jumping around a little....
anyway I replaced all the fuses with the correct amp and then checked the lights tonight in the dark. Thought this would help since what does work has been dim.

BIG PROBLEMS!

First I turned on the parking lights, key in OFF.
The left turn signal in the dash lit up dim.
Parking lights to the front came on, but not to rear.

Key still in OFF, left turn signal:
"CHOKE" light blinks!!!!

Key ON parking lights on:
still no rear parking lights

Key ON, left turn signal:
parking lights blink!

Key ON, right turn signal:
parking lights blink

Key on, turn signal, plus brake
everything stops blinking.

This is soooo mesed up I'm starting to think
head light switch has internal short in it.

Anybody else?????

thanks
 
sounds like the printed circuit has a bad ground or short hence the different incorrect blinking lights
could also be the turn signal switch playing games with the key off no turn signal anything should work

Start at the fuse block and trace the wires back to the back like you are doing, if he had really bad butt connecter or taped wire splices for long enough some of the wiring may be corroded and ruined. I'm talking replacing as little as 2"-6" of wiring as much as the entire length depending on the moisture exposure. Or if you like check from the brake lights forward. Make sure each tail light bucket has a ground in the wiring near by and that the light sockets aren't melted when the connecters contact, probably wouldn't hurt to spray a little contact or electrical parts cleaner and use a little dielectric grease when reinstalling.

Make sure you also have the following ground straps... motor to frame, frame to body around the firewall, radiator support and tailgate. battery to frame and body.
 
Id place money on a grounding problem. Thats close to what mine was doing when the ground was bad, cept mine, with the turn signal on and hitting the brakes, I got police style wig-wags....to bad I couldnt keep just that feature lol.
 
Update

You guys nailed it! Ground problem on the rear.

The grounding wires the PO installed were not tied into the wiring harness by the tail lights, and therefore did not do too much.

I redid the grounds at the rear and also the ground from the engine to fire wall.

The brake and turn signals work now, but no parking lights or dash lights.

After lunch I get to dive into that probelm.

On a related note, the driver tank was all rusted out in the front. About a 12" by 12" area stays wet with fuel. Luckily, my brother has a spare tank.

thanks for the help
 
No parking lights or dash lights....are we just talkin side markers, or are you talking no parking lights at all, front rear side? Could be the headlight switch. Maybe a loose plug on it, IIRC there are 2 or 3 different plugs on the back of it, dont really know what they do, maybe one came off?
 
No dash, side marker, or front or rear parking lights.
I replaced the fuse and it blew again in about 1 second.

I spent about an hour looking for where the hot wire could be getting grounded out, but could not find any.

I checked the fuse location with my multimeter with the fuse removed.
With the switch on...
The right half is hot (12.4v) and the left half is grounded.
With the switch is off...
Neith side shows powered or grounded.

This leads me to believe the switch is good and the problem is somewhere in the wiring at or past the firewall.

This make sense to anybody??
The problem now is I cannot find any problems.

Could the problem be around the gage cluster?
I really need to study a wiring diagram, but I so much like looking at it in person.

thanks again
 
Goose said:
I checked the fuse location with my multimeter with the fuse removed.
With the switch on...
The right half is hot (12.4v) and the left half is grounded.
With the switch is off...
Neith side shows powered or grounded.
Click to expand...
thats reading correctly...the fuse gives power to the left half


Is the fuse blowing with just regular running lights on?

If its not the only difference is the head lights being on which would lead me to the head light switch.....however thats not definate, no dash lights and no tail lights its a direct corrolation that tells you something isn't right if the dash lights aint on
 
Check this and tell me if it works or not and i'll give you my across the internet diagnosis

truck ignition ON but not running does right and left turn signals work? Front and rear?

can you turn on your head lights without blowing a fuse? If it blows what about with the ignition OFF can you turn on your headlights, what about parking light mode?

if all that works when you turn on a turn signal does it blow? if not is it when you hit the brakes?

Oh yeah what year model vehicle and fuse number is blowing?
 
Okay...
Key On, truck not running all turn signals work.

Fuse blows when head light switch pulled out to first notch for parking light mode. Headlights work when pulled out to second notch.

Brakes/turn signals do not blow the fuse.

It's a '86 K30, the fuse is the "T/L CTSY", 20A

I've been distracted by learning my other gas tank leaks.....ALOT.
Found one for $45, plus my brother has one when he makes in from out of state.

anyway, I'm getting closer and the projects are multiplying
thanks.
 
Last edited:
I'll have to double check mine but thats more than likely in the headlight switch if it does in position 1 but not 2 if you can reliably drive around in position 2 with functioning brake and turn signals and dash lights its definately in the switch
 
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