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Discussion Starter #1
this is a 97 GMC pickup diesel 6.5. When you start the truck the head lights come on automatically & as soon as I turn on my headlight on manually using the switch, they turn off. Why does this happen? thanks
 

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The DRL's light when the ignition is on. If your light go out when the switch is on, then you most likely have a bad switch. How do you drive the truck at night? Are you only seeing the DRL indicator on the dash go off, or are the lights actually going off?
 

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Cheap and easy fix? Try your parks.
 

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the wiring in your tilt steering coloumn has broken at the connecter to your high beam low beam switch when you start truck it is drl's on when you hit switch it turns them off but headlights don't come on because wiring is broken i see this on vehicles that people raise the wheel every time they get out they pull the lever and wheel "bang" to the top every time.
 

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Discussion Starter #5
The parking lights work when you put the switch to that, when you turn on the headlights they come off, but the daytime running lights are still on.
 

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The DRL's are the same light (low beam lamp), just a little dimmer, so it hardly makes a difference.

I usually run with the DRL's at night towing to keep the bright light out of the eyes of oncoming drivers because the front end of the trucks is slightly elevated.
 

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Discussion Starter #7
well im just trying to narrow down the problem. When I put the switch to parking lights work, im trying to figure out why the headlights dont work. Its either the switch or the wiring in the stering colum which I think it is.
 

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The dash switch is pretty common problems with these, I took mine apart and cleaned the contacts and put a light coat of dielectric grease on everything again and haven't had a problem for a couple years.
 

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First off, The DRL on the 97 uses the high beam lamps at approx 40% brightness so, to the guy towing with the DRL only on, you're blinding people even more, so, cut it out and be normal.

Secondly, since the DRL uses the high beam lamps at approx 40% brightness, turning on the headlamps and having the low beams not come on indicates that you a: have both low beam bulbs burned out; b: have a faulty dimmer switch; c: have a faulty light switch.


-Daniel
 

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First off, The DRL on the 97 uses the high beam lamps at approx 40% brightness so, to the guy towing with the DRL only on, you're blinding people even more, so, cut it out and be normal.


-Daniel
Umm, no. My DRL's use the low beam light, and all fullsize GM trucks from 94-up with composite lamps that I have seen use the low beam lamp (trucks with sealed beams may be different). So, thanks for your advice, but I will continue to be "abnormal".
 

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Your head light switch is bad. Junk money making part for GM.
 

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I did see this once on an old Ford. I thought the switch took a dive, come to find out, BOTH low beams went at the same time... so don't rule out the simple stuff.
 

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Umm, no. My DRL's use the low beam light, and all fullsize GM trucks from 94-up with composite lamps that I have seen use the low beam lamp (trucks with sealed beams may be different). So, thanks for your advice, but I will continue to be "abnormal".
Gonna disagree with you there. DRL's do use the high beam at 40% - at least they do on my truck.

IIRC:
On my 94 - the DRLs and high beams are the inside the composites, and the low beams are the outside composites.

On my dad's 97 - the DRLs and high beams are the outside comosites, and the low beams are the inside composites.
 

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My '97 uses the low beams (outside lights) for DRL. Why anyone would bypass the DRL's is beyond me. It is much easier to see vehicles with DRL's

Bill
 

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Here are some pics:

DRLs


Dims


Brights
 

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I think there is a difference in the 94 DRL vs. 95-up, or there is a difference with Canadian spec trucks. I stand corrected on my earlier statement that all 94-up trucks use the low beam lamp for DRL's, but I know how my 97 headlamps work. My sister had a 94 Sub that was a Canadian truck, and I remember that the DRL's did work with the high beams. There is absolutely no way that some trucks use the inside lamp for low beams, though. All of the composite headlights from 88-2000 in our body style trucks are the same, and the high beam and low beam lenses are designed differently for different light patterns.

Because of the way my 97 works, I am confused by what the original poster in this thread is saying. When I switch from DRL's to low beams, there is only a slight difference in the amount of light (definetely not a 60% reduction, more like 10%), and it is really hard to tell the difference. That is why I drive with the DRLs and my parking lamps on when towing (and only in well lit areas with plenty of street lights). I think it reduces the glare for other drivers when the front end of the truck is up (due to a heavy trailer), but probably makes no difference, but it might extend the life of my low beam bulbs.
 

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When I switch from DRL's to low beams, there is only a slight difference in the amount of light (definetely not a 60% reduction, more like 10%), and it is really hard to tell the difference.
Then there must be some differences throughout the years becuase as you can see in my pics, there is a huge difference in brightness between the DRLs in pic 1 and the Brights in Pic 2. Even my dims in pic 2 are brighter than my DRLs in pic 1
 

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My 1995 is exactly the same setup as yours Chris. Inside lights are DRL's and high beams when activated. The outside lights are for low beams alone.

I believe the setup changed in 1996. The outside lights are the DRL's and Low beams and the insides are the highs. Why they changed this who knows....The 96' and up DRL's do look brighter than mine so i wouldn't be suprised if it is hard to see the difference as those here with 97's are claiming. The difference between my DRL's (high beams on low power) and my low beams is very noticable.
 

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1990-1994 trucks drl are high beam wires in series to reduce brightness. 1995-up trucks use outside light-low beam through a diode to reduce brightness. If your headlights do not work it could also be the headlight relay which is located in the convenience center down by your left foot.
 

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Discussion Starter #20
well I first checked the switch. I took one of another truck but still nothing. Then I took apart tht tilt colum there and noticed tht the wiring there was burned. I fixed tht up and now it works :) thanks for all ur help guys
 
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