Headlight turn on without turning on light switch

[AK49BWL]

The push button trick doesn't work until the 99-02 GMT800 lineup lol.

 

[delkaandrew]

Update sorry, been dealing with personal issues.
I recently discovered by accident when replacing the headlight switch, thinking that was the issue, that whenever I press on the parking break (with the headlight switch in the off position) the headlight will finally turn off and you can operate the switch as intended. There is a click sound when this happens, like a relay. Went through and switched relays under the dash around and nothing fixed it. I still had the same issues. It doesn’t cause any safety issues, it’s just annoying because it never did this prior to be rebuilding the front end after accident.

 

[Keeper]

Your issue has been answered multiple times and ways. Did you read the link from post #4?

As stated, if your rear and/or side marker lights are not on also, then it is just your Daytime Running Lights (DRL). Pull the fuse that says DRL if it is bothering you (20A fuse #15 on left dash panel). The DRL's also go off when you push the parking brake. Some people leave the fuse in and just push the parking brake down one click to get them to turn off and stay off. Maybe you, or the po, had the parking brake clicked down one notch before the accident.

 

[delkaandrew]

It’s not my DRL’s that are the issue. I read the previous posts and threads. Pressing the parking break down one click does fix the issue of the low beams turning on without the switch. However the green dash indicator for the DRLs goes away and I want that to stay on the dash when DRLs aren’t in use, and the break light now comes on which would make me assume my parking brake would obviously be engaged and possibly prematurely wear out?
I’ll re read the previously posted thread and see if I missed something.
I appreciate the feedback.

 

[delkaandrew]

pull the drl fuse ?

Did that, just disengaged the DRLs. I want to keep the DRLs and still be able to turn them on via the switch.

 

[Keeper]

My head hurts. Why would you want the green DRL indicator lamp to be on when the DRLs are off? If you use the switch, you are turning on all of the running lights also, not just the DRLs.

edit: DRLs use your low beams, it is the same bulb

 

[Nad_Yvalhosert]

Pressing the parking break down one click does fix the issue of the low beams turning on without the switch.

As stated, that is not an "issue". It's an OE designed system that is factory installed, and is now in proper working order.

Pressing the parking (correctly spelled) B R A K E pedal one click is also an OE designed "lamp defeat" feature.

Now, when you say the low beams come on, do the front amber and rear red lights come on too?
If so you have automatic lights via a twilight sentinel sensor on your dash. My '00 Yukon Denali has this...
If not, then the DRL uses the low beam filiment as intended.

 

[Nad_Yvalhosert]

However the green dash indicator for the DRLs goes away and I want that to stay on the dash when DRLs aren’t in use,

You can't. It's not wired that way and never will be.
DRLs lit, green light lit.
DRLs off, green light off.

 

[delkaandrew]

You can't. It's not wired that way and never will be.
DRLs lit, green light lit.
DRLs off, green light off.

That’s interesting, I’ve had this truck almost 6 years and the green light has always been lit when the front DRLs are off and vise versa. I just thought that’s how it was meant to be, my buddies 98 is the same way. As far as the low beams, they are on and the front ambers are off and the rear lights are off as well. So I’m pretty confident they aren’t automatic. I was not aware that was the OE design, when I pulled the DRL/FOG fuse it did fix the issue from what you have said. I just thought it didn’t because the green light disappeared. My mistake, I apologize for the confusion. That’s why this forum is here haha
(I know how to spell brake, must’ve autocorrected ) I appreciate all the input guys thanks!

 

[Road Trip]

Hello all, a little back story.
I was in a four car pileup a year ago and decided to rebuild the whole front end of my truck. When putting it all together and plugging in all the wires to the headlights back in I noticed that when I turn the key to acc power the low beams turn on without needing to turn the headlight switch. It didn’t use to do that prior to the rebuild. Is it possible the switch has gone bad? I’ve already tried unplugging and reinstalling the connectors and putting dielectric grease on. Am I missing something or has anyone else had this issue?

Greetings delkaandrew,

Whenever I perform a major repair, *if* there is a behavioral change before vs after I may or may not
choose to pursue it. Even so, I always want to know why the behavior change occurred, so that my
decision whether or not to fix is based upon fact, instead of just hoping that the behavioral change is benign.
So I get why you are questioning this change in behavior, especially since it's related to the electrical system.

So let's take a look at the DRL circuit as documented in the '97 C/K FSM, and let's see if the circuit is
working as advertised. Before diving into the actual diagrams, let's see what the General has to say
about when the DRLs should be operational:

You must be registered for see images attach

You must be registered for see images attach

OK, your observation that the DRL headlights are now working (post accident) with the Ignition switch in the
'ACC' position is *not* a design feature, but a change in behavior. (Per the last sentence on the 2nd page.)
We'll keep this in the back of our mind for later.

Update sorry, been dealing with personal issues.
I recently discovered by accident when replacing the headlight switch, thinking that was the issue, that whenever I press on the parking break (with the headlight switch in the off position) the headlight will finally turn off and you can operate the switch as intended. There is a click sound when this happens, like a relay. Went through and switched relays under the dash around and nothing fixed it. I still had the same issues. It doesn’t cause any safety issues, it’s just annoying because it never did this prior to be rebuilding the front end after accident.

The DRLs being disabled by the parking brake pedal being engaged is correct. (Like others have shared.)
And you are hearing the DRL Relay being de-energized by the DRL Module. Here's a picture of exactly where
the DRL Relay is located on the Convenience Center:

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If you get a chance, pull the DRL Relay and verify that you have not only disabled
the function, but also you have removed the relay click when you activate the
parking brake. (ie: we know that we are in control of the circuit that is fed by
the DRL relay, and this will also help to orient you in the wiring diagram later on.)

That’s interesting, I’ve had this truck almost 6 years and the green light has always been lit when the front DRLs are off and vise versa. I just thought that’s how it was meant to be, my buddies 98 is the same way.

I underlined the word 'operating' in the sentence on the 2nd page where the manual describes that
the DRL indicator in the instrument cluster mirrors the status of the headlights. Keeping score,
during the shock of the accident did we add a new problem with the DRL headlights being on
while in ACC, but also fixed the DRL display in the dash so that it now works as advertised?
Stranger things have happened. :0)

Hopefully I've piqued your interest enough that you can't wait to wade around in the
following diagram:

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A lot of folks aren't that comfortable with the wiring diagrams, but I find that if I really want to
know the true behavior of a circuit, the wiring diagram is the troubleshooter's holy grail.
(as long as it's drawn accurately. :0)

For example, if you locate Pin G on the DRL module, you'll see that it not only turns on the
Relay (by applying a ground) but it also turns on the 'Daytime Running Lamp' indicator in the
instrument panel.

And for anyone else reading this who would like to disable the DRLs yet keep their fog
lights operational, this diagram shows you that simply pulling the DRL Relay will do just that.

****

So what about the DRLs working in the ACC position? Well, the FSM has a troubleshooting
flow for the DRLs being on when they shouldn't be:

You must be registered for see images attach

Reading through the flowchart, they make mention of the DRL (control) Module, not to be confused with the
Diode or the Relay. Since I'm up against the 5-pic limit, I'll talk about that in the next reply.