Both low-beam headlights went out simultaneously - 2013 GMC Sierra SLE

[Shadovin]

Both my low beams went out simultaneously, while I was driving home.

I have replaced the associated fuses and the relay, both in the fuse box under the hood, but the problem persists.

 

Any solutions?  Bulbs appear to be in good shape
High beams working fine

Emergency and fog light working fine

[Bleepster]

did you trace and check the pigtail connectors for power?  where the fuses/relays bad?  have power at the fuse/relay area?

Edited April 24, 2023 by Bleepster

[richard wysong]

check to see if you have power and ground at the headlight connector. possible bad dimmer switch if there is no power

[Shadovin]

So, interesting solution to the problem.

 

The relay was bad.  However, it wasn't completely none functional.  So, likely over the last few days the relay has been sending variable power instead of consistent power.  
So, while the bulb itself worked, the installation of the new relay provided too much consistent power to a weakened bulb that was already fraying, on the element.

The problem likely would have been fixed with the relay replacement, however, there were two different bulbs installed.  One was a Sylvan, the other was some generic no name bulb.  That bulb is what what blew out with the new relay and was apparently frayed the most due to the originally faulty relay.

I was told that this problem is also often associated with a burn out bulb at the license plate.  If your vehicle has a plate bulb, a burnout of that bulb can mess with your headlamps.

[richard wysong]

Welcome to the Forum! Thank you for posting  the results, I'm sure it will help someone in the future and we all learn from it.