Well drat. I had an excuse to make a grocery run and while out I could not get the lights to go out by pressing the dome-light override switch. I was behind a truck at a stop-light so I could see the reflection of my DRLs in the tailgate. I tried slower and faster, 3, 4 and 5 pushes of the button but Nada.

Do people think it could be because my Blazer was originally made for Canada?* Perhaps for them at the time, the ability to disable the DRLs and auto-headlights was disabled?
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* I think it was intended for Canada because the Computer Climate Control was in Celsius and on the RPO decode, but not when I got it 10 years ago, it has a speedometer listed to be in kilometers.

 

Just a thought, does your override button work for turning your dohme light off when your door is open? If not, maybe that part of your headlight switch is bad. I had to change my headlight switch the other day, everything worked except dash lights.

 

Thanks for suggesting the idea but my dome override button does work to disable the dome light. I've used it many times. I Since it works the button itself is likely ok but now I'm curious enough to look through my schematics to see how that button is hooked up to things. I'm sure the BCM must be involved somehow.

 

Post what you figure out if you dont mind, I'd be curious to know how it works myself. The more I think about it, a button that shuts off an entirely different circuit by switching on and off a few times seems a little odd lol

 

Well, looking at the schematics that have the headlamp switch in them, pressing the dome override switch connects the "Dome Override Input" of the BCM to ground. This must be the logic input signal the BCM uses to decide to disable power that goes to the dome-lights. I can easily imagine this same input being used for an input consisting of a sequence of toggles of the input signal. Whatever is going on, it is part of the logic programming of the BCM. How the BCM is programmed and which you have will be determined by what options the vehicle was to have. I'm guessing it wasn't to be for me. :-)

I still might play with the how I used the dome override button but I guess I'm stuck rigging my own override circuit. It has definitely become a personal challenge now! LOL

P.S. I just now looked at the Wikipedia article on DRLs. Canada made DRLs mandatory starting in about 1990. To reduce costs, GM started adding them to the US vehicles too starting in about 1995. DRLs have never been mandatory in the US although GM did try to get them to be mandatory in the late 2000s (the late "naughts"). So perhaps my BCM or its programming is different.

P.P.S. I remembered I had the CarFax for my Blazer and sure enough, it was first sold and registered in Alberta and a year later it was imported to the US then put up for sale at a dealership in Seattle with mileage of about 16,900 miles.

 

Never would've thought of all that. Great info. Wonder If theres a fuse or relay that only powers DRL and could be disabled

 

Yes the override works for the dome light from what I have read don't switch override trick doesn't work on a 1999