Brake Lights only work with light pedal press.

[zutuu1967]

Howdy,
I have a 96 K1500 and as the title suggests, the brake lights only come one at the very top of the pedal travel. It started when I replaced the bulbs in the third brake light. Something shorted out with the old rusty housing and I blew the brake light fuse and the interior light fuse. I replaced both of those and the third brake light housing. Once I noticed the weird brake light problem had popped up, I replaced the brake light switch and the relay to no avail. I have noticed some folks saying that the multi switch could be an issue. I’m wondering if that could be my problem. The cruse works fine and the brake disengages it, but I noticed today that the right turn signal only comes on about half of the time I use it. I still get the the clicks, but no turn signal or light on the cluster. Any thoughts?

Thanks.

 

[Nad_Yvalhosert]

It started when I replaced the bulbs in the third brake light. Something shorted out with the old rusty housing and I blew the brake light fuse and the interior light fuse. I replaced both of those and the third brake light housing.

What happens when you unplug the CHMSL/cargo light assy altogether?

Once I noticed the weird brake light problem had popped up, I replaced the brake light switch and the relay to no avail.

Is it adjusted correctly?

I have noticed some folks saying that the multi switch could be an issue. I’m wondering if that could be my problem. The cruse works fine and the brake disengages it,

Always a possibility, especially as the CHMSL and cruise have their own brake signal inputs from the brake switch, but the brake lights route through the multi-function assy.

but I noticed today that the right turn signal only comes on about half of the time I use it. I still get the the clicks, but no turn signal or light on the cluster. Any thoughts?

Another symptom of a bad multi-function switch: bad internal contacts.

So, what're you gonna check next? Unfortunately I can't reach through the internets and do it for you...

 

[zutuu1967]

The issue stays the same when I unhook the cargo light assembly. I’ve tried two different brake light switches and I don’t see anywhere on either one for adjustments. Am I missing something there? I’ve searched high and low for instructions on adjusting them, but all I have seen is some vague stuff about about a lever that neither of my switches have.

 

[Nad_Yvalhosert]

The issue stays the same when I unhook the cargo light assembly. I’ve tried two different brake light switches and I don’t see anywhere on either one for adjustments.

If the CHMSL works as designed, the brake switch is not to blame. Continue on with L&R brake light diag:
Is there a poorly installed trailer hitch wiring connector interrupting the circuit?
If so, does the trailer function correctly?
How about the tail light wiring ground connection?

 

[zutuu1967]

That’s for the tips. I climbed under the truck today and found two problems. The black wire on the trailer connection was broken, so I fixed that. I also found a very sketchy ground connection. It was barely touching the frame. I found a better spot, cleaned it and the connectors really good with a wire brush. While I am glad to have those two things fixed, it did not affect the issue whatsoever. I am going to try replacing the trailer light harness and see if that does it.

 

[zutuu1967]

Well no luck with the trailer light harness. I did a bit more troubleshooting under the dash. If I reach above the pedal and push the brake light switch forward, the brake lights come on. With a very gentle touch of the pedal they come on. If I push the switch forward, and depress the pedal at the same time so that the switch is still engaged, they still turn off about 1/3 through the pedal travel. Is there some other switch or relay attached to the brake pedal that I should be looking at? Also, I am able to shift into gear without pressing the pedal.

 

[GoToGuy]

Somebody has by passed the shift interlock. The center high brake gets its power before the turn signal combo switch. That's why it does not flash. If center functions normally let it be. Test the brake switch on out put side. With test light. As you press brake pedal does it light the go out with the rake lights or stay lit?