OK...Here's a new one

[wxman1]

A friend of mine noticed that my right side tail light/brake
light goes out when I press the brake pedal. Both the tail light
and the brake light (both filaments) turn off. This only happens
when the light switch is on and the brake pedal is pressed. Is
the brake light switch (under the dash) the culprit?...or possibly the headlight switch is causing this?...or is
this more complicated?

Anybody else have this problem?

Thanks!
Jim
Mt Juliet

[wxman1]

I also discovered that after taking off the lenses...that
he right side tail light is not as bright as the left side...
go figure.

Jim

[72MARIO]

Checked the grounds yet ? That would be you dim bright problem for sure. Fix that and you may have corrected the light's turning off when you use the brake.

[68cajun]

sounds like a ground problem to me.

[purple gas]

if it's not the ground today, it will be some day. Clean 'em up cause bad grounds can cause all kinds of greif

[cdowns]

a definte wortwhile project is to clean(shiney metal on shiney metal) your grounds and it doesn't hurt to coat them with dielectic grease while you're at it

[wxman1]

I did check the ground on the taillight fixture and it looks good. So the taillight is grounded to the bed and the bed is
bolted to the frame. The negative side of the battery is
connected to a bolt in the exhaust header. So it seems to me
that the ground circuit should be completed. Do you guys have
ground straps that connect the bed to the cab and etc?

Jim
Mt Juliet

[pjmoreland]

There should be two grounding straps at the rear of the engine that attach the engine to the cab. There should be a grounding strap that connects the cab to the chassis, down on the front passenger side cab mount. There should be a grounding strap that connects the passenger side inner fender to the chassis, up under the battery. There should be star washers at each end of each grounding strap between the grounding strap and the metal it is attached to.

I don't think there is anything wrong with your brake switch, because otherwise nothing would turn off when pressing the brake.

[pjmoreland]

The two tail lamps are connected to the same voltage source (brown wires), so if one tail lamp is on and the other tail lamp is not on, then it seems like there must be a grounding issue.

[armyavncowgirl]

Originally Posted by wxman1

I did check the ground on the taillight fixture and it looks good. So the taillight is grounded to the bed and the bed is
bolted to the frame. The negative side of the battery is
connected to a bolt in the exhaust header. So it seems to me
that the ground circuit should be completed. Do you guys have
ground straps that connect the bed to the cab and etc?

Jim
Mt Juliet

I'm an electrician and I can tell you that you need to start looking from where the wiring harness breaks off to each side of the tail since its only your right side that is the problem. I wouldn't worry about everything north of that because if the switch or ground were the problem BOTH tail lights would go out. So, where your harness splits off between the two lights is where I would start off. First place I would look is at the taillight itself, its possible some wires are crossed or a bad socket. Check the socket, if you see any residue, whether it be white or green or even rust, i would take a wire brush to it and perhaps some contact cleaner (thats what we in the Army call it---you might call it corrosion cleaner). I would focus on the plug that goes into the taillight and then move forward from there.

[pjmoreland]

I did check the ground on the taillight fixture and it looks good.

How did you verify that the ground is good? Did you use a test light or an ohm meter? Grounding can be tricky. Even if all of the parts are connected together, there can be small layers of rust between the parts that mess up the ground path. My license plate lamp wasn't working one time, and all I had to do to get it working again was to tighten the bumper bolts a little. I also had a reverse lamp that wasn't working. I tightened the screws that hold the reverse lamp housing to the bed, and it started working again. In my experience, the vast majority of electrical problems are caused by bad grounding, or bad switches, neither of which can be fixed by hacking into the wiring harness, which only introduces more problems.

[Longhorn Man]

As for the brake light going off...chainge the bulb.

[wxman1]

I did change the bulb with a known good bulb...no diference. I also ran a separate
ground wire from the taillight fixture to bare metal on the cab...no difference.
I think I'll check out the connections at the taillight fixture in the morning
to see if something is not making good connection. I might as well check
the connector at the tail light harness while I'm under there.

Thanks for all the good suggestions!

Jim
Mt Juliet

[Longhorn Man]

does that turn signal work in back?

[wxman1]

Problem solved.

I ran a long wire directly from the tail light fixture to the battery negative terminal
to try and eliminate the possibility of a bad ground. No change...light still goes out
when the brake pedal was pressed. I got the voltmeter out and checked both
contacts...12v on the tail light contact and 12v on the brake light contact. So...
I wiggled the bulb and sure enough the tail light brightened up and it also stays on
when the brake light is pressed. So...for the 3rd time I pulled the assembly out and
tried to clean the barrel of the light fixture. No luck...but that has to be the problem.
So I took a pair of vise grips and slight warped the barrel. bulb fits sort of tight...
but it now makes good contact. Since I'll probably replace both tail light fixtures
anyway...I guess there's no harm done...and it works!

Jim
Mt Juliet