Brake lights 1998--switch adjustment?

Hi all.
This '98 Tahoe has a new twist I haven't seen mentioned. I thought the brake lights weren't working because they weren't coming on when I'm driving. This problem started a couple weeks ago. So yesterday I changed the pedal switch and still nothing changed. No brake lights. All other lights worked correctly.

Then I was pressing the pedal almost to the floor and near the bottom of pedal travel the brake lights all came on as they used to; both sides and the high mount. So if I mash them to scorched Earth, they work. Normal driving, no.

I'm positive if I exchanged the new switch for the old one the same thing would occur. A year ago I had the master cylinder replaced and the brakes have been spongy since. He said it was hard to get the air out of the anitlock system and I think it's still there. The brakes are awful. The dealer said they've sometimes run 8 qts through to get the air out.

How could this brake light thing have just started and could it be related? the cruise still shuts off as soon as I hit the brake.

there is no adjustment. but that is unusual. by lights come on within 1/2 inch of depressing the pedal. if yours operates the same distance roughly for killing cruise control or TC lockup then I would assume something is wrong wit the switch.

there should be no relation to sponginess. The master cylinder should have been bled first before connecting lines. and the chances of getting air in the circuits that would effect abs operation are rare.

Thanks. That gives me some insight into how it works. Yes the cruise and lockup circuit work just as they always have. And the brake lights worked in that same short travel until recently. Does it mean that I have power into the switch if Cruise and Lockup operate?

Actually, it sounds like I have the same problem as one person posted somewhere, maybe not this site. A broken wire rubbing against a raw metal opening severed his wire.

Today the brake lights don't work at all. I'm thinking all the hard pedal depressing to show how hard it is to make them work has stretched the wire until it broke completely? If that's the problem the excess pedal travel of the bad master cylinder job has probably accelerated the problem.

I need to find that wire--and that post. If I can determine that I have power in to the switch it's a matter of tracing the wire out to the lights.

Part 1 of 2
Turn, Hazard, Park, Marker, & Stop Lamps Notes

Turn And Hazard Lamps/Park And Marker Lamps (Part 1 Of 2)


Part 2 of 2
Turn, Hazard, Park, Marker, & Stop Lamps Notes

Turn And Hazard Lamps/Park And Marker Lamps (Part 2 Of 2)

Thanks. Does that say ORN for ORANGE hot to the stop switch in the upper right?

The thing I see different is that I don't have a relay under the hood that is shown. I see the 4 white wires exiting the switch (at top right) one to cruise so that must mean I have power to the switch if it operates (and also because I had lights yesterday with HARD braking). Another white one goes to UTILITY which is what? Is that the lock up torque convertor, maybe? One goes to the relay and one looks like it goes to the haz switch on the other side. Once there Lt Blu comes from the Haz switch to the trailer tow.

Since I have a fault in the trailer harness and pedal, it sounds like I have a wiring issue to me.

SunlitComet said:

Part 1 of 2
Turn, Hazard, Park, Marker, & Stop Lamps

Notes

Turn And Hazard Lamps/Park And Marker Lamps (Part 1 Of 2)


Part 2 of 2
Turn, Hazard, Park, Marker, & Stop Lamps

Notes

Turn And Hazard Lamps/Park And Marker Lamps (Part 2 Of 2)

Click to expand...

ORG means orange. the relay does not apply to utility vehicle which in our case is designated a Tahoe. it is used in the truck or chassis-cab bodies. that one labeled C goes to the center high stop leds. there are more wires on that switch then shown above.

It turned out to be a broken WHITE wire from the brake light switch pigtail where it goes into another connector. I had to pull the steering column to remove that pig tail. Where it plugs into the otherr connector it's attached to something that holds the pigtail up off the column. The WHITE wire was severed right where it plugs in to that connector. There's a sharp metal piece cutting the pigtail wires. I believe it was also due to the extended travel in my brake pedal which is caused by air in the anti-lock system. It scraped the pigtail over and over and since it's fastened down at the other end it final broke a wire by cutting into it. Two other wires are also cut through the insulation. I don't think it would've happened without the slop in my pedal.

The fix is to repair the wire, move the connector to allow more travel and get all the air out of my brake system. I wish I hadn't allowed the mechanic to suggest replacement of my master cylinder.

glad you found the wire nut extended travel in pedal should have never been part of the cause unless someone was screwing it.

Thank you for this thread!

I have had the problem with my brake lights only coming on when i mash the pedal to the floor. I replaced the brake light switch, and then I lost my brake lights all together, then realized that I had also lost cruise control. I found this forum, read your thread about the wire being damaged next to the connector, with a nice picture. So I contorted under the dash with a headband light, and sure enough! damaged wires. The only things that I had to remove was the screw holding the wire cluster directly below the steering wheel, and the brake light switch. It took about an hour to get it out, I soildered the wires back together, then covered them in heat shrink, and reinstalled everything in about 35 minutes. I cant thank you guys enough for your time and valid information.


Your new friend, Jeff

I had the EXACT SAME problem on my 2000 Yukon Denali old body style. I changed both the brake switch and the turn signal assembly just to have, you guessed it, no brake lights. I am so glad you posted this on here. I did a search and found this thread.
So I dug a little deeper and found the same broken wire on the brake switch harness. Seems to be a common problem for these for sure.
Thanks again, guys for updating this so I could find this problem.
Mike