brake lights no worky!!

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Ontheboulder

Full Access Member
Joined
Feb 27, 2022
Posts
310
Reaction score
365
Location
colville,wa
First Name
greg
Truck Year
1987
Truck Model
gmc sierra classic v2500
Engine Size
350
hey all new here on this! this has probably been asked a million times but here I go. 1987 gmc sierra classic,v 2500. no brake lights! I had the left one working but not the right. the right turn signal was not working,so I tried switching the flasher,voila both turn signals are working, the 4 ways are working,the tail lights are working but I lost the left rear brake light that was working prior to changing the flasher.So neither side brake lights are working. Fuses are good.bulbs are good,. I have power into and out of the brake light switch, Orange wire constant hot and white wire lights up when the brake peddle is depressed.I have un- plugged the harness at the rear of the truck everything but brake light power!! Any ideas!!??? scratching my head here!!
 

Rusty Nail

Full Access Member
Joined
Jan 29, 2015
Posts
9,786
Reaction score
9,681
Location
the other side of the internet
First Name
Rusty
Truck Year
1977
Truck Model
C20
Engine Size
350sbc
Got any pics of the taillights?
Show us what youre workin with!


xc_hide_links_from_guests_guests_error_hide_media
 

Ontheboulder

Full Access Member
Joined
Feb 27, 2022
Posts
310
Reaction score
365
Location
colville,wa
First Name
greg
Truck Year
1987
Truck Model
gmc sierra classic v2500
Engine Size
350
sorry I don't just stock tail lights. This all started with just fixing the dashboard right turn signal indicator.after replacing all the gauge lights.got the dash light fixed but still no right rear turn of brake light, Both of the fronts work fine! Thinking it was just a bad light socket, nope.so after digging around on the internet,some said to just replace the flasher. well the flasher was working for the left side and the 4 ways but I changed it anyway.with the new flasher I got the right rear turn to work as well as the rest but lost my left brake light Hence no brake lights,even put the old flasher back in, still got both turns signals but no brake lights
 

Ontheboulder

Full Access Member
Joined
Feb 27, 2022
Posts
310
Reaction score
365
Location
colville,wa
First Name
greg
Truck Year
1987
Truck Model
gmc sierra classic v2500
Engine Size
350
Like I said everything was working except the right rear turn and brake signal,now everything works except the brake lights.NO wiring has been done just bulbs and headlight switch replaced.
 

Ontheboulder

Full Access Member
Joined
Feb 27, 2022
Posts
310
Reaction score
365
Location
colville,wa
First Name
greg
Truck Year
1987
Truck Model
gmc sierra classic v2500
Engine Size
350
I un plugged the rear lights from the harness running down the frame rail to the rear of the truck to check that as well. all good except for brake light power
 

fast 99

Full Access Member
Joined
Dec 31, 2021
Posts
1,626
Reaction score
2,201
Location
Spokane, Washington
First Name
Brian
Truck Year
81,85
Truck Model
K20
Engine Size
350
Find the brake light switch under the dash. Should be power standing on one side, when the pedal is depressed, both should have power.
 

Ontheboulder

Full Access Member
Joined
Feb 27, 2022
Posts
310
Reaction score
365
Location
colville,wa
First Name
greg
Truck Year
1987
Truck Model
gmc sierra classic v2500
Engine Size
350
Yup did that orange wire constant power,white wire lights up when the peddle is depressed
 

Ontheboulder

Full Access Member
Joined
Feb 27, 2022
Posts
310
Reaction score
365
Location
colville,wa
First Name
greg
Truck Year
1987
Truck Model
gmc sierra classic v2500
Engine Size
350
another thing I tried was with the turn signal activated,pressing on the brake peddle. the turn signal-either side does not cancel for the brake light
 

Ontheboulder

Full Access Member
Joined
Feb 27, 2022
Posts
310
Reaction score
365
Location
colville,wa
First Name
greg
Truck Year
1987
Truck Model
gmc sierra classic v2500
Engine Size
350
this stuff will drive a guy to drink!!! Heavily!!
 

JoeR Jr

Full Access Member
Joined
Jun 23, 2018
Posts
191
Reaction score
241
Location
Stokesdale, NC
First Name
Joe
Truck Year
1986
Truck Model
C10
Engine Size
6.0/4L80E
Remember that brake light power has to go through the turn signal switch in order to get to rear bulbs. They do this so the same bulbs can be used for both turn signals and brake lights. So your next move is to check brake light input into, and out of, the turn signal switch.

So that would be:
White wire is brake power into the switch.
Dark green and yellow would be power out.
 
Last edited:

Ontheboulder

Full Access Member
Joined
Feb 27, 2022
Posts
310
Reaction score
365
Location
colville,wa
First Name
greg
Truck Year
1987
Truck Model
gmc sierra classic v2500
Engine Size
350
Remember that brake light power has to go through the turn signal switch in order to get to rear bulbs. They do this so the same bulbs can be used for both turn signals and brake lights. So your next move is to check brake light input into, and out of, the turn signal switch.

So that would be:
White wire is brake power into the switch.
Dark green and yellow would be power out.
 

WP29P4A

Full Access Member
Joined
Jul 18, 2021
Posts
866
Reaction score
1,469
Location
Nevada
First Name
Mike
Truck Year
1987
Truck Model
Sierra Classic V1500
Engine Size
350 TBI
I would check the grounds for the tail lights, then the ground from bed to cab.
 

Ontheboulder

Full Access Member
Joined
Feb 27, 2022
Posts
310
Reaction score
365
Location
colville,wa
First Name
greg
Truck Year
1987
Truck Model
gmc sierra classic v2500
Engine Size
350
thank you!! I have been reading that the brake light power seems to go into and through the turn signal switch.then on to the brake lights. this seems to be where i am at,
 

Ontheboulder

Full Access Member
Joined
Feb 27, 2022
Posts
310
Reaction score
365
Location
colville,wa
First Name
greg
Truck Year
1987
Truck Model
gmc sierra classic v2500
Engine Size
350
I would check the grounds for the tail lights, then the ground from bed to cab.
I think all the grounds are good as every other light circuit is working, just no brake lights. starting to think it is in the turn signal switch, that may have to go to the shop to get done,not sure about doing it my self
 

Ontheboulder

Full Access Member
Joined
Feb 27, 2022
Posts
310
Reaction score
365
Location
colville,wa
First Name
greg
Truck Year
1987
Truck Model
gmc sierra classic v2500
Engine Size
350
I replaced a turn signal switch in a 72 Chevy I had years ago,but it didn't have all the multi function switch stuff like this thing has. windshield wiper, High beam and the cruise control ,might be better to let my buddies shop take care of it ,if that's what it turns out to be
 

Forum statistics

Threads
42,124
Posts
909,607
Members
33,616
Latest member
pete08
Top