Left brake light not working sometimes - The 1947 - Present Chevrolet & GMC Truck Message Board Network

D-Day · 06-06-2008, 11:54 PM

It's being funky as hell. I got stopped by a cop the other day and he told me about it, but he didn't ticket me because the light wasn't out. The 4-ways work, the left turn signal works, just when the brake is down it sometimes didn't work.

Then it started working again.

Then it started malfunctioning again.

It seems like when it's not working, if I flip the left turn signal, it'll start working again. Something is amiss here. Anybody have any ideas on where to look for the short/wiring problem? It's not the bulb.

GM72K10 · 06-07-2008, 07:00 AM

Check all the grounds, check for any loose-kinked-ready to break wires.

Mickey_D · 06-07-2008, 08:54 AM

Yup, pull the whole light assembly and check the ground wire that goes to the fender. Mine was doing the exact same thing, except I had to physically get out and smack the side of the truck right in front of the light to get mine to work.

Also check that the bulb and socket are clean. Some dielectric grease in there is always a good idea, too.

James McClure · 06-07-2008, 08:56 AM

D Day, Your problem is in the signal light switch itself. The switch cuts off brake light power to the side your signaling. When the switch is in "Neutral" brake light power goes to both sides. When it's not working jiggle the switch lever. If it comes on, replace the switch. Jim

D-Day · 06-07-2008, 11:19 AM

Thanks a lot guys, it really helps knowing exactly what/where it is. I'm leaving for a camping trip, 800 miles+ one way on Monday. Don't need trouble with the law.

Also, where exactly is the turn signal switch? Is it just the turn signal fuse?

And where exactly is the ground on the fender? I know this is dumb, but in case it's not made obvious to me when I start looking, I just like to ask these questions in advance to get a lead time.

James McClure · 06-09-2008, 07:54 AM

D-Day, OK, first there is the fuse, like any other, next is the flasher unit. The flasher unit is nothing more than a self reseting circut breaker and last is the switch itself located under the steering wheel and the lock plate. Grounds, 1 behind the L\rear tail light assembly and 2 on the radiator support. The switch is pretty straight forward to change unless you have a tilt wheel. If your not comfortable with small parts or steering colunms, have someone else change it out for you. Have a safe trip, jim

SRH916 · 06-09-2008, 11:54 AM

mine was doing the same thing, and not sure 100% about this, but i cleaned the ground for my licensplate lamp and it started working... might be your problem.

06-06-2008, 11:54 PM	#1
D-Day Live fast, die young Join Date: Sep 2006 Location: Northwest Ohio Posts: 293	Left brake light not working sometimes It's being funky as hell. I got stopped by a cop the other day and he told me about it, but he didn't ticket me because the light wasn't out. The 4-ways work, the left turn signal works, just when the brake is down it sometimes didn't work. Then it started working again. Then it started malfunctioning again. It seems like when it's not working, if I flip the left turn signal, it'll start working again. Something is amiss here. Anybody have any ideas on where to look for the short/wiring problem? It's not the bulb.

06-07-2008, 07:00 AM	#2
GM72K10 Next! Join Date: Jan 2003 Location: Eastern Pa. Posts: 2,483	Re: Left brake light not working sometimes Check all the grounds, check for any loose-kinked-ready to break wires. __________________ 86 K30 CUCV M1028A1 86 K30 CUCV M1028a2 dually 86 K30 C&C 6.2 4:56s, 4M, 11,000 gvw, ex fire truck, now lowboy dump More square bodies and CUCVs than I care to admit to 2020 Silverado K3500HD Work truck

06-07-2008, 08:54 AM	#3
Mickey_D Dirteh Kitteh Join Date: Nov 2006 Location: Mormon country Posts: 2,484	Re: Left brake light not working sometimes Yup, pull the whole light assembly and check the ground wire that goes to the fender. Mine was doing the exact same thing, except I had to physically get out and smack the side of the truck right in front of the light to get mine to work. Also check that the bulb and socket are clean. Some dielectric grease in there is always a good idea, too. __________________ Darrin 1955 Willys CJ-5 all original and the oldest CJ-5 on the road. 2001 Dodge Neon (wife's car) 1995 Jeep Grand Cherokee Limited Edition SOLD 1981 K15 Custom Deluxe 4X4, rusty but trusty wood hauler. SOLD 1993 S-10 4X4 Tahoe SOLD Sign up with the Contact List RIP ESLL

06-07-2008, 08:56 AM	#4
James McClure One shot, one kill. Join Date: Dec 2007 Location: Saratoga Springs NY Posts: 859	Re: Left brake light not working sometimes D Day, Your problem is in the signal light switch itself. The switch cuts off brake light power to the side your signaling. When the switch is in "Neutral" brake light power goes to both sides. When it's not working jiggle the switch lever. If it comes on, replace the switch. Jim __________________ 1984 K20 350M engine with 465,000 miles. Well, it's finally done!! Almost 2 years of work, but it was really worth the effort. Little stuff left to do is mount winch, wet sand & buff out and build belly pan\running boards. Body work takes lots and LOTS of beer!!!! God, Guts and Guns made America and God, Guts and Guns will preserve it! The worst thing you could do is get into my sights, but that don't matter, you'll never know it, cause you'll never hear the shotJim or Paladin whichever you choose.

06-07-2008, 11:19 AM	#5
D-Day Live fast, die young Join Date: Sep 2006 Location: Northwest Ohio Posts: 293	Re: Left brake light not working sometimes Thanks a lot guys, it really helps knowing exactly what/where it is. I'm leaving for a camping trip, 800 miles+ one way on Monday. Don't need trouble with the law. Also, where exactly is the turn signal switch? Is it just the turn signal fuse? And where exactly is the ground on the fender? I know this is dumb, but in case it's not made obvious to me when I start looking, I just like to ask these questions in advance to get a lead time. Last edited by D-Day; 06-07-2008 at 11:19 AM.

06-09-2008, 07:54 AM	#6
James McClure One shot, one kill. Join Date: Dec 2007 Location: Saratoga Springs NY Posts: 859	Re: Left brake light not working sometimes D-Day, OK, first there is the fuse, like any other, next is the flasher unit. The flasher unit is nothing more than a self reseting circut breaker and last is the switch itself located under the steering wheel and the lock plate. Grounds, 1 behind the L\rear tail light assembly and 2 on the radiator support. The switch is pretty straight forward to change unless you have a tilt wheel. If your not comfortable with small parts or steering colunms, have someone else change it out for you. Have a safe trip, jim __________________ 1984 K20 350M engine with 465,000 miles. Well, it's finally done!! Almost 2 years of work, but it was really worth the effort. Little stuff left to do is mount winch, wet sand & buff out and build belly pan\running boards. Body work takes lots and LOTS of beer!!!! God, Guts and Guns made America and God, Guts and Guns will preserve it! The worst thing you could do is get into my sights, but that don't matter, you'll never know it, cause you'll never hear the shotJim or Paladin whichever you choose.

06-09-2008, 11:54 AM	#7
SRH916 1975 C-10 Silverado LWB Join Date: Nov 2007 Location: Sacramento, CA Posts: 326	Re: Left brake light not working sometimes mine was doing the same thing, and not sure 100% about this, but i cleaned the ground for my licensplate lamp and it started working... might be your problem. __________________ 1975 LWB C-10 Silverado - Stock - "BIG 10" - 4 Bolt 350 "Brand new" 1200mi - THM-375 "Brand new w/trans cooler" 5000mi 1995 Ford Lightning - Bone Stock - 351W - Vortech??



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