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
366
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 have several grounds, cab to frame,bed to frame,battery to frame and engine, not sure just what else i may have missed,not sure on a ground from cab to the bed though,will check into that
 

Ontheboulder

Full Access Member
Joined
Feb 27, 2022
Posts
310
Reaction score
366
Location
colville,wa
First Name
greg
Truck Year
1987
Truck Model
gmc sierra classic v2500
Engine Size
350
what has got me stumped, is that why I had the left rear brake light working,and the right rear brake and turn not working,then by replacing the flasher i had both turn signals working but no brake lights??? The 4 ways are working fine?? just seems weird that the flasher change made this difference
 

WP29P4A

Full Access Member
Joined
Jul 18, 2021
Posts
889
Reaction score
1,514
Location
Nevada
First Name
Mike
Truck Year
1987
Truck Model
Sierra Classic V1500
Engine Size
350 TBI
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
Your theory would be good if the whole lighting circuit was grounded together, but it's not. Your truck has several "local" grounds, near each set of lights. The body and frame of the truck is the ONLY thing tying the grounds back to the battery. If you pull out one of the tail light housing you will find a ground location, if you look on your radiator support near your headlights you will find the grounds for the headlights, etc. You also should have several ground straps to link your bed to the frame and the cab to the frame, and the engine to the firewall.

So if the ground for the tail lights is not good, the only set of lights it will effect is the tail lights.
 

Ontheboulder

Full Access Member
Joined
Feb 27, 2022
Posts
310
Reaction score
366
Location
colville,wa
First Name
greg
Truck Year
1987
Truck Model
gmc sierra classic v2500
Engine Size
350
Your theory would be good if the whole lighting circuit was grounded together, but it's not. Your truck has several "local" grounds, near each set of lights. The body and frame of the truck is the ONLY thing tying the grounds back to the battery. If you pull out one of the tail light housing you will find a ground location, if you look on your radiator support near your headlights you will find the grounds for the headlights, etc. You also should have several ground straps to link your bed to the frame and the cab to the frame.

So if the ground for the tail lights is not good, the only set of lights it will effect is the tail lights.
good point!! I will go back and double check all the ground points tomorrow , grounding will cause a lot of head scratching!! thanks for your input
 

AuroraGirl

Full Access Member
Joined
Sep 8, 2019
Posts
9,693
Reaction score
6,869
Location
Northern Wisconsin
First Name
Taylor
Truck Year
1978, 1980
Truck Model
K10, K25
Engine Size
400(?), 350
You must be registered for see images attach
 

WP29P4A

Full Access Member
Joined
Jul 18, 2021
Posts
889
Reaction score
1,514
Location
Nevada
First Name
Mike
Truck Year
1987
Truck Model
Sierra Classic V1500
Engine Size
350 TBI
As far as the WHY? If you change a load or voltage to a device like a set of lights that had a marginal connection to begin with sometimes it will jump the connection and make it work again temporarally until the heat or weather changes again and the connection "opens". It only takes minute changes to make a bad connection come and go due to heat/cold, moisture, vibration, change in voltage or load.

That's why TIGHT connections are so important.
 

WP29P4A

Full Access Member
Joined
Jul 18, 2021
Posts
889
Reaction score
1,514
Location
Nevada
First Name
Mike
Truck Year
1987
Truck Model
Sierra Classic V1500
Engine Size
350 TBI
Also Dc voltage is a sneaky bugger, it you take away it's main path back to the battery it will try to find another path. "The path of least resistance" When the voltage finds it's way back to the battery through another circuit it will create false symptoms. Like the brake lights only work when the turn signals are on.
 

WP29P4A

Full Access Member
Joined
Jul 18, 2021
Posts
889
Reaction score
1,514
Location
Nevada
First Name
Mike
Truck Year
1987
Truck Model
Sierra Classic V1500
Engine Size
350 TBI
You must be registered for see images attach
This is the perfect example, connector looks good but it's between rusted sheet metal and a rusted bolt. The is the perfect scenario where just a little moisture with make this connection work until it drys out or a little vibration breaks the connection causing intermittent operation of brake lights.
 

Ontheboulder

Full Access Member
Joined
Feb 27, 2022
Posts
310
Reaction score
366
Location
colville,wa
First Name
greg
Truck Year
1987
Truck Model
gmc sierra classic v2500
Engine Size
350
thanks to you all!!! tomorrow will be check ,double check and re-enforce all the grounds,If that fails I think I will start drinking heavily!! LOL
 

AuroraGirl

Full Access Member
Joined
Sep 8, 2019
Posts
9,693
Reaction score
6,869
Location
Northern Wisconsin
First Name
Taylor
Truck Year
1978, 1980
Truck Model
K10, K25
Engine Size
400(?), 350
This is the perfect example, connector looks good but it's between rusted sheet metal and a rusted bolt. The is the perfect scenario where just a little moisture with make this connection work until it drys out or a little vibration breaks the connection causing intermittent operation of brake lights.
oh that bitch had no working anymore the sockets were falling apart if you handled haha! Fixed it now but that was an exaple of yikes + the ground location on the bed
 

AuroraGirl

Full Access Member
Joined
Sep 8, 2019
Posts
9,693
Reaction score
6,869
Location
Northern Wisconsin
First Name
Taylor
Truck Year
1978, 1980
Truck Model
K10, K25
Engine Size
400(?), 350
thanks to you all!!! tomorrow will be check ,double check and re-enforce all the grounds,If that fails I think I will start drinking heavily!! LOL
If you start your drinking moderately with water and not empty stomach you may wake up rememebring the step to continue
 

Matt69olds

Full Access Member
Joined
Jan 8, 2018
Posts
2,451
Reaction score
3,819
Location
Central Indiana
First Name
Matt
Truck Year
81
Truck Model
GMC 1/2 ton
Engine Size
455 Olds
Check for power on the green and yellow wires at the turn signal switch connector while pushing the brake pedal. If not, most likely the turn signal switch is defective
 

Ontheboulder

Full Access Member
Joined
Feb 27, 2022
Posts
310
Reaction score
366
Location
colville,wa
First Name
greg
Truck Year
1987
Truck Model
gmc sierra classic v2500
Engine Size
350
Do you have the correct lamp in the tail light socket? It should be an 1157. Sometimes, I've seen incorrect lamps or installed incorrectly. Just a quick thought.
Yup checked that a few times
 

Latest posts

Forum statistics

Threads
44,173
Posts
950,864
Members
36,288
Latest member
brentjo
Top