Left And Right Side Brake Lights Inop

glafemina · April 25, 2009

I have a 99 Silverado (newer body style) 4x4 ext cab that both left and right side brake lights dont work. Although the brake light on the cab works. I have no power to the stop lamp fuse in the engine compartment fuse box. Also no power at electrical connector under the tailgate for stop lamps. Note:all other exterior and interior lights operate normal. Turn signal,cruise, and hazards all

work normal to. Due for state inspection(NJ) this month(April), running short on time. Thanks for help in advance.

bill190 · April 25, 2009

Is there another Stop light fuse inside the cab?

If not and the fuse in the engine compartment is the only fuse for this, then how are you measuring to see if there is voltage at the fuse or not?

I would test this with a multimeter set to DC voltage, connect the black lead of the multimeter to battery negative (using an alligator clip test wire), remove the fuse, then test both connections where the fuse goes to see that one had power (12V).

Then I would set the multimeter to ohms and place both tests leads on the fuse connections (fuse removed) to see if there was continuity. The same as if I touched both test leads together when set to ohms.

It seems to me that if the cab stop light is working, then one stop fuse is also working. And if the fuse under the hood is the only stop fuse, then this should be working???

It is possible there is a "truck" stop fuse and a separate tail/trailer stop fuse. And also possible that the cab stop light is on another circuit than the tail light stop lights. (Anything is possible with vehicles!)

Anyway the only way to tell for sure what all components are involved with the stop light system and where these components are located is by looking at a factory wiring diagram for that specific year/vehicle. Otherwise we are just guessing!

glafemina · April 25, 2009

"Is there another Stop light fuse inside the cab?"

I belive there was one, and I have power to that fuse. I have just been using a test light, and also for test purposes I replaced those fuses for test purposes, and still no left and right brake lights.

If not and the fuse in the engine compartment is the only fuse for this, then how are you measuring to see if there is voltage at the fuse or not?

Using my test light,I also have a digital multi meter, although I didnt see the need for it at this time.

I would test this with a multimeter set to DC voltage, connect the black lead of the multimeter to battery negative (using an alligator clip test wire), remove the fuse, then test both connections where the fuse goes to see that one had power (12V).

Did that basically with the test light, if I had a blown fuse I would have power on one side of the fuse and not the other, and I dont have power on either side the fuse in the engine compartment for the brake light.

Then I would set the multimeter to ohms and place both tests leads on the fuse connections (fuse removed) to see if there was continuity. The same as if I touched both test leads together when set to ohms.

I swapped in known good fuses, and still same result.

It seems to me that if the cab stop light is working, then one stop fuse is also working. And if the fuse under the hood is the only stop fuse, then this should be working???

It is possible there is a "truck" stop fuse and a separate tail/trailer stop fuse. And also possible that the cab stop light is on another circuit than the tail light stop lights. (Anything is possible with vehicles!)

It appears the third brake light or brake light on cab is on a seperate circuit than the brake lights on the bed.

Anyway the only way to tell for sure what all components are involved with the stop light system and where these components are located is by looking at a factory wiring diagram for that specific year/vehicle. Otherwise we are just guessing!

That is why I am hear asking for help, I appreciate your time and your response.

bill190 · April 25, 2009

On other models "Brake" goes to ABS, "Stop" goes to the brake lights. Other than that, you're going to need a factory wiring diagram. (No one here seems to have ever purchased wiring diagrams except for me and mine is for the 1992 model year.)

Also fuses many times go to several things. Like I think on my truck, "Stop" goes to brake lights, the warning chime, the Hazard lights, and ABS memory.

And something like ABS can have 3 different fuses for it! One for memory, one to operate the electronics, and a fusible link for the pump motor.

Anyway the factory wiring diagram will say what all a particular fuse goes to. And will show the source of power to the fuses - where various things are connected.

glafemina · April 26, 2009

I have power to the one fuse on the left side of the dash but thats for ABS. Although no power to the fuse in the engine compartment for the brake lamps. I have power going to several pins on the brake lamp switch and the turn signal switch, but not power to all.