how do daytime running lights work on 1995 S-10? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**dmjlambert** · 03-04-2023, 12:27 AM

I have a 1995 S-10 pickup base model. I think the daytime running lights work when the headlights are off but engine is running and they seem to be partial brightness. How is that partial brightness done? I am wondering if there is a module of some sort that sends a pulse width modulated signal to the lights, essentially making them blink on and off fast enough so a human eye can't see the blinking, or if there is a relay that puts the headlights in series with each other to cut the voltage in half, or some other method.

The reason I'm asking is the normal operation of the headlights is malfunctioning, they are very dim, and I would like to go to the module or relay and check the voltages there (where ever that is). I'm only getting about 6 V at the headlight when headlights are on, and about 3 V when headlights are off for daytime running lights.

Just call me Sean · 03-04-2023, 04:53 AM

I know how mine work. The module goes in the glove box and I turn them on and off with my hand.

**dmjlambert** · 03-04-2023, 12:08 PM

I played with a multimeter last night and I am developing an idea that when the main headlight switch is off, a relay is used to put the high beam filaments of the right and left sides in series with each other to turn them on and make them half brightness. I pulled the fuse for the daytime running lights, so now I just have normal headlights only when I want them. I'll have to figure out what part is causing low voltage for my normal headlight function. It is probably a bad connection, fuse, relay, or switch somewhere.

After a lot of searching online I finally found some wiring diagrams mentioned/linked here by forum member s10dude on s10forum.com:
https://www.s10forum.com/threads/s-s.../#post-8057868
Which leads me to here:
https://drive.google.com/drive/folde...KCj02rRuAaVwlA
I had to figure out how to navigate the google drive folders, double click on them because single click doesn't work.

And I have a 1995 S/T truck service manual on order via eBay, but although it is a nice fat manual I don't know if it really has any good stuff in it. I will see when it gets here.

I wish this forum had some more activity in the S10 section.

03-04-2023, 12:27 AM	#1
dmjlambert Senior Member Join Date: Apr 2016 Location: Cypress, TX Posts: 3,859	how do daytime running lights work on 1995 S-10? I have a 1995 S-10 pickup base model. I think the daytime running lights work when the headlights are off but engine is running and they seem to be partial brightness. How is that partial brightness done? I am wondering if there is a module of some sort that sends a pulse width modulated signal to the lights, essentially making them blink on and off fast enough so a human eye can't see the blinking, or if there is a relay that puts the headlights in series with each other to cut the voltage in half, or some other method. The reason I'm asking is the normal operation of the headlights is malfunctioning, they are very dim, and I would like to go to the module or relay and check the voltages there (where ever that is). I'm only getting about 6 V at the headlight when headlights are on, and about 3 V when headlights are off for daytime running lights.

03-04-2023, 12:08 PM	#3
dmjlambert Senior Member Join Date: Apr 2016 Location: Cypress, TX Posts: 3,859	Re: how do daytime running lights work on 1995 S-10? I played with a multimeter last night and I am developing an idea that when the main headlight switch is off, a relay is used to put the high beam filaments of the right and left sides in series with each other to turn them on and make them half brightness. I pulled the fuse for the daytime running lights, so now I just have normal headlights only when I want them. I'll have to figure out what part is causing low voltage for my normal headlight function. It is probably a bad connection, fuse, relay, or switch somewhere. After a lot of searching online I finally found some wiring diagrams mentioned/linked here by forum member s10dude on s10forum.com: https://www.s10forum.com/threads/s-s.../#post-8057868 Which leads me to here: https://drive.google.com/drive/folde...KCj02rRuAaVwlA I had to figure out how to navigate the google drive folders, double click on them because single click doesn't work. And I have a 1995 S/T truck service manual on order via eBay, but although it is a nice fat manual I don't know if it really has any good stuff in it. I will see when it gets here. I wish this forum had some more activity in the S10 section.



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