Weird tail light issue!

[Yo]

I have a strange tail light issue I'm trying to figure out.

What happens is that one of the taillights will go out, but the other will stay on when I hit the pedal. If I turn on the headlight switch, both taillights work, but when I hit the brakes, only one brake light.

Then, if I pull the hazard light switch and then turn it off, and hit the brakes, both work until I turn on the headlights, in which case one of the brake lights will not respond to the pedal.

It will switch between the driver and passenger side, but seems to prefer the passenger more. I have to keep pulling the hazards to "reset" the brake lights for them both to work.

Is this a faulty brake light switch? It's not the bulbs, obviously. Can we round out a short given the issue moves from side to side? Perhaps a blinker switch gone bad since the hazards are able to make the issue go away?

Any suggestions?

 

[K5_Fla]

I hate these types of electrical issues.. they always suck. First thing... dont assume the bulbs are always good. Bulbs can be tricky.... start there....change them out and report back. It's real cheap, fast and easy to do.

 

[Jeff Carr]

I would also pull the taillight housings and check the grounds. I had crazy taillight issues in one of my K5's and it turned out the grounds were rusted out.

 

[boz42]

Mine did the same thing. My issue was a bad ground.

 

[K85 Octane]

wow, make sure to reply with a solution once you find one

the front blinkers switch back and forth because of they share the same ground, but one gets cut off when the other is on. The rear brake lights, running lights, and reverse lights are all separate IIRC. All three screw into the same ground location. The large bulb has both brake and running modes, so it is probably the one giving you problems.

running lights get their power from the headlight switch, so that might be causing problems too. Just not sure where the brake light comes into play. It's not the brake switch on the pedal, it's only on or off.

 

[4X4HIGH]

I hate these types of electrical issues.. they always suck. First thing... dont assume the bulbs are always good. Bulbs can be tricky.... start there....change them out and report back. It's real cheap, fast and easy to do.

X1

I had a very similar issue once and it was a bad bulb.

Don't discount a bad bround somewhere though as that is usually the result of most electrical failures.

 

[blazinzuk]

Oddly enough most of the weird tailight problems I have had in the past involve the blinkers

 

[diesel4me]

The two filaments in tail lamp bulbs can touch if one filament fails ,and will cause all kinds of weirdness!..bad grounds are a common fault too,and sometimes a directional signal switch has contact problems..also do not overlook any trailer hitch wiring that may have been added,often its done shoddily or gets damaged and causes all kinds of troubles--..later 88 & up trucks had issues with the printed curcuit boards in the tail lamp sockets corroding and failing too...

 

[Yo]

OK, well here's what we can factor out:

Bulbs are brand new, I initially thought it was a bad bulb and replaced only to see the problem persist.

The headlight switch is also brand new, I installed it a few months ago, so I'm pretty sure we can factor that out as well.

I'll pull the taillight buckets and check the grounds and sockets and report back.