Brake Lights - The 1947 - Present Chevrolet & GMC Truck Message Board Network

bouncytruck · 07-12-2004, 11:26 AM

I just discovered my brake lights aren't working. I'm going to have to work on it tonight when I get home from work but I'd like to (hopefully) narrow down my troubleshooting before I get started.

The tail lights and turn signals work - just the brake lights aren't. What is the most likely cause?

I did pressure wash the underside of the truck yesterday. As far as i know, the brake lights were working before that.

**Stocker** · 07-12-2004, 11:41 AM

Quote:

Originally Posted by bouncytruck

The tail lights and turn signals work - just the brake lights aren't. What is the most likely cause?

Bad brake light switch? Without going out to look for it, I think it's near the brake pedal, activated by the movement of the pedal.

Lippyp · 07-12-2004, 11:54 AM

Broken wire? If it's the original wire it can get pretty brittle. Mine is a horrid rats nest of spliced in bits of wire and all the insulation is rock hard. It's a job for the winter making a new loom as my lights are adapted for UK regs. Check the wiring.

JimKshortstep4x4 · 07-12-2004, 12:52 PM

If the taillights and turn signals are working, then the wiring from the turn signal switch back is good. Your brake switch routes power to the turn signal switch which routes the power to the bulbs in the rear lights. Your problem has to be between the power and the brake light switch or between the brake light switch and the turn signal switch, (including the brake light switch).

Good luck!

Jim

Maximum Overdrive · 07-12-2004, 12:53 PM

I had a problem with the plug that connects to the switch on mine.

bouncytruck · 07-12-2004, 01:02 PM

I was thinking it might be the brake light switch. I'll start there. If I put the the multi-meter where the brake light fuse is at, will that give me any indication of where my problem is?

JimKshortstep4x4 · 07-12-2004, 01:09 PM

You should be able to read power on one wire to the switch. Power should be there whether the ignition switch is on or not. With the brake pedal depressed, both wires to the brake light switch should read 12 volts.

If you don't get power past the switch, it is bad or needs adjusting.

Jim

vtblazer · 07-12-2004, 01:28 PM

I had the same thing happen once...they just stopped working.
After the normal bulb check, I found that the switch had just stuck.
Lubed it up some and it's been fine since.
It's located above the brake pedal assembly (no kidding) Take it out and free it up, should do it.

bouncytruck · 07-12-2004, 01:35 PM

VT - what did you lube the switch with? I looked under there this morning and it appears to be moving when I press the pedal - but it is still worth checking.

vtblazer · 07-12-2004, 01:45 PM

If memory serves...I cleaned it with WD-40 and lubed it with grease.(I think)
If you have a meter, just check it while it's out. It's simply a switch...make or break...check for contact.

sactoC10 · 07-12-2004, 02:04 PM

ditto here,

I wrestled and stressed over the same symptoms for a while, thinking it was the rear harness, grounds etc... Turned out that the switch simply needed to be adjusted and it kinda works backwards. I took mine out, but left it plugged in and got myself in position to see whether or not messing with it would activate the lights. Sure enough, they were fine, very small area of adjustment for my switch, took 3 tries to get it working right with the pedal.

good luck!

franko72 · 07-12-2004, 06:07 PM

your flat four probably has been spliced at one time for a trailer . just some loose connections ,or maybe some blown bulbs due to a short when ya washed it

bouncytruck · 07-12-2004, 06:15 PM

Franko - what do you mean by "flat four"? I have a receiver hitch on my rig - very clean install on the wiring. What you are saying makes sense - they were working before pressure washing.

franko72 · 07-12-2004, 06:25 PM

the flat four is the standard wiring to most rear end brake, running lights , and turn signals. They are four wires That are all adjoined side to side in one strip. Seems to me that they were working before you pressure washed . did you wash under the rear bed? if so maybe you just disturbed a connection point to your wiring. have someone hold down the brake pedal while lightly pulling and tugging at some of the connection points at the wiring and see if the brake lights flicker. good luck.

bouncytruck · 07-12-2004, 06:51 PM

Yes, I did wash under the bed. I'll take a look at those connections first. It sounds like the most likely scenario.

This board is great! Thanks for all the help everyone!

07-12-2004, 11:26 AM	#1
bouncytruck SKINNY TIRES RULE! Join Date: Sep 2001 Location: Bothell, WA Posts: 11,038	Brake Lights I just discovered my brake lights aren't working. I'm going to have to work on it tonight when I get home from work but I'd like to (hopefully) narrow down my troubleshooting before I get started. The tail lights and turn signals work - just the brake lights aren't. What is the most likely cause? I did pressure wash the underside of the truck yesterday. As far as i know, the brake lights were working before that. __________________ bouncytruck 1972 K5 The Hauler 1994 K1500 Suburban The Daily2010 Kia Soul Wife's Ride2014 Fiat 500L

07-12-2004, 11:54 AM	#3
Lippyp English Chevy Owner Join Date: May 2002 Location: Shropshire, UK/ Lot, France Posts: 1,848	Broken wire? If it's the original wire it can get pretty brittle. Mine is a horrid rats nest of spliced in bits of wire and all the insulation is rock hard. It's a job for the winter making a new loom as my lights are adapted for UK regs. Check the wiring. __________________ Phil '67 C10 long fleet. 350/TH350, 4 bbl Carter, K&N, Dual exhaust, loads of stuff coming soon 2001 S10 Blazer Daily Driver, bone stock 4 door 4x4 with manual transmission

07-12-2004, 12:53 PM	#5
Maximum Overdrive December 21, 2012 Join Date: Apr 2000 Location: Black Eagle, Montana Posts: 1,633	I had a problem with the plug that connects to the switch on mine. __________________ *"!Ama Sua, Ama Kjella, Ama Lllulla!"*

07-12-2004, 01:02 PM	#6
bouncytruck SKINNY TIRES RULE! Join Date: Sep 2001 Location: Bothell, WA Posts: 11,038	I was thinking it might be the brake light switch. I'll start there. If I put the the multi-meter where the brake light fuse is at, will that give me any indication of where my problem is? __________________ bouncytruck 1972 K5 The Hauler 1994 K1500 Suburban The Daily2010 Kia Soul Wife's Ride2014 Fiat 500L

07-12-2004, 01:28 PM	#8
vtblazer Registered User Join Date: Oct 2003 Location: Central Vermont Posts: 8,537	Brake Lights I had the same thing happen once...they just stopped working. After the normal bulb check, I found that the switch had just stuck. Lubed it up some and it's been fine since. It's located above the brake pedal assembly (no kidding) Take it out and free it up, should do it.

07-12-2004, 12:52 PM	#4
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	If the taillights and turn signals are working, then the wiring from the turn signal switch back is good. Your brake switch routes power to the turn signal switch which routes the power to the bulbs in the rear lights. Your problem has to be between the power and the brake light switch or between the brake light switch and the turn signal switch, (including the brake light switch). Good luck! Jim

07-12-2004, 01:09 PM	#7
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	You should be able to read power on one wire to the switch. Power should be there whether the ignition switch is on or not. With the brake pedal depressed, both wires to the brake light switch should read 12 volts. If you don't get power past the switch, it is bad or needs adjusting. Jim

07-12-2004, 01:35 PM	#9
bouncytruck SKINNY TIRES RULE! Join Date: Sep 2001 Location: Bothell, WA Posts: 11,038	VT - what did you lube the switch with? I looked under there this morning and it appears to be moving when I press the pedal - but it is still worth checking. __________________ bouncytruck 1972 K5 The Hauler 1994 K1500 Suburban The Daily2010 Kia Soul Wife's Ride2014 Fiat 500L

07-12-2004, 01:45 PM	#10
vtblazer Registered User Join Date: Oct 2003 Location: Central Vermont Posts: 8,537	Switch If memory serves...I cleaned it with WD-40 and lubed it with grease.(I think) If you have a meter, just check it while it's out. It's simply a switch...make or break...check for contact.

07-12-2004, 02:04 PM	#11
sactoC10 71 DELUX Join Date: Sep 2003 Location: Northern CA / Sac Posts: 1,055	ditto here, I wrestled and stressed over the same symptoms for a while, thinking it was the rear harness, grounds etc... Turned out that the switch simply needed to be adjusted and it kinda works backwards. I took mine out, but left it plugged in and got myself in position to see whether or not messing with it would activate the lights. Sure enough, they were fine, very small area of adjustment for my switch, took 3 tries to get it working right with the pedal. good luck! __________________ 5/4 drop LWB wood bed - 15x8 front 235/60 - 15x10 rear 295/50 2003 FORD Escape 1998 Honda VTR1000

07-12-2004, 06:07 PM	#12
franko72 Franko72 Join Date: May 2004 Location: Cincinnati,Ohio Posts: 471	your flat four probably has been spliced at one time for a trailer . just some loose connections ,or maybe some blown bulbs due to a short when ya washed it __________________ 1972 C20 cheyenne Super 402 BB/400 turbo LWB A/C Tilt, Cruise Control, Saddle tanks, Tach My Home Page Better to burn out than it is to rust

07-12-2004, 06:15 PM	#13
bouncytruck SKINNY TIRES RULE! Join Date: Sep 2001 Location: Bothell, WA Posts: 11,038	Franko - what do you mean by "flat four"? I have a receiver hitch on my rig - very clean install on the wiring. What you are saying makes sense - they were working before pressure washing. __________________ bouncytruck 1972 K5 The Hauler 1994 K1500 Suburban The Daily2010 Kia Soul Wife's Ride2014 Fiat 500L

07-12-2004, 06:25 PM	#14
franko72 Franko72 Join Date: May 2004 Location: Cincinnati,Ohio Posts: 471	the flat four is the standard wiring to most rear end brake, running lights , and turn signals. They are four wires That are all adjoined side to side in one strip. Seems to me that they were working before you pressure washed . did you wash under the rear bed? if so maybe you just disturbed a connection point to your wiring. have someone hold down the brake pedal while lightly pulling and tugging at some of the connection points at the wiring and see if the brake lights flicker. good luck. __________________ 1972 C20 cheyenne Super 402 BB/400 turbo LWB A/C Tilt, Cruise Control, Saddle tanks, Tach My Home Page Better to burn out than it is to rust

07-12-2004, 06:51 PM	#15
bouncytruck SKINNY TIRES RULE! Join Date: Sep 2001 Location: Bothell, WA Posts: 11,038	Yes, I did wash under the bed. I'll take a look at those connections first. It sounds like the most likely scenario. This board is great! Thanks for all the help everyone! __________________ bouncytruck 1972 K5 The Hauler 1994 K1500 Suburban The Daily2010 Kia Soul Wife's Ride2014 Fiat 500L

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