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Chevy Suburban Daytime Run Lights

Posted: Wed Oct 03, 2007 6:36 am
by ljbeng
The run daytime lights on my Suburban are on all the time. There is a photosensor in the rear view mirror that points toward the windshield. Is that sensor supposed to turn the lights on if the daylight gets a little low? Has anyone torn apart the Chevy mirror to get to the electronics? Would the photo sensor go bad or is there a relay stuck shut somewhere? Thanks.

Posted: Wed Oct 03, 2007 10:32 am
by haklesup
The Daytime running lamps (DRL) option keeps the lights on low beam as long as the car is powered on. This is a required feature in cars sold in Canada but AFAIK they are generally not optioned in US sold vehicles except maybe some fleets. If your car is used, check the VIN online to see whare it was made. DRL generally has nothing to do with a sensor, it is controlled by a module near the headlamps under the hood.

Seperately, some cars especially newer ones have auto sensing headlights and in my car, the sensor is a little bump in the dashboard covered with plastic similar to a remote control. The sensor in the rear view mirror is strictly for the electrochromic auto dimming feature of the mirror. I can select auto or manual headlamp operation at the headlamp switch so its easy to know what mode I'm in. ... 53/c-10101[/url]

Posted: Wed Oct 03, 2007 10:45 am
by gerty
Mine (98 Silverado ) shut off when I apply the emergency brake. The switch is mounted near the end of travel, you can press the pedal down about a 1/2" and the drl's shut off. There is a dash indicator, green I think, that let's you know if they are on or not..

Posted: Wed Oct 03, 2007 11:23 am
by ljbeng
I remember someone trying the parking brake trick but then the parking brake light came on.... Maybe I can find the switch and force it closed. Thanks.

Posted: Wed Oct 03, 2007 11:30 am
by gerty
On mine the parking brake light doesn't come on untill you press the pedal down at least 2", that's about when the brake actually engages. Incidentally, on mine the drl's are the low beam headlights..

Posted: Wed Oct 03, 2007 1:39 pm
by dacflyer
some systems have 2 seperate switches, one for the brake light indicator and the other for the DRL's

as for the sensor in the mirror, its probably a day time / night time feature that adjust the mirror

as for the sensor in the dash,,i had a vehicle that it would turn on the head lights if it got too dark and you forgot to turn them on.
nice feature, especially if you live in the city and theres a lot of street lights,,hard to tell if you have your lights on at all sometimes,
i see many around here that do that,,( forgetting to turn them on.

Posted: Wed Oct 03, 2007 2:10 pm
by ljbeng
Here is a little from the manual. This is a 1999.

"The DRL system will make your headlamps come on at a reduced brightness when:
Ignition is on,
Headlamp switch is off and
Parking brake is released."

"When it begins to get dark, your DRL indicator light is a reminder to turn your head lamp switch on."

I think I totally mis-read this. I thought it meant when the daylight was at reduced brightness, the lamps come on. It means the lights come on at a reduced brightness. OOPS.

It's not a big deal but in a small town <900 people, they all wonder why that dad-blane fool drives around with his lights on all the time....:)

Posted: Wed Oct 03, 2007 3:06 pm
by jwax
Tell them its a way to save money on your car insurance. :grin:

Posted: Wed Oct 03, 2007 5:28 pm
by jollyrgr
There is a fuse on the driver side internal fuse block that disables the DRL. It is labeled DRL or similar and this is the only thing (at least on my brother's 96) on the fuse.

Posted: Wed Oct 03, 2007 6:36 pm
by philba
ljbeng wrote:...
It's not a big deal but in a small town <900 people, they all wonder why that dad-blane fool drives around with his lights on all the time....:)
A lot of people always drive with their light on. It's considered a safety feature. In fact, my 2006 Volvo ALWAYS has it's headlights on.

Posted: Wed Oct 03, 2007 8:44 pm
by Robert Reed
My '97 Blazer also came with "daytime headlights" and when I purchased it new, i was not fond of this feature. But as time went by, i grew to really like it especially around twilight when you are most apt not to turn your headlamps on. It wasn't until recently that I learned this is not a mandatory feature,as I had always assumed that if GM gave it to me, the government made them do it.
I do notice that on long road trips the majority of cars are lit during daytime hours.

Posted: Thu Oct 04, 2007 5:56 pm
by jollyrgr
I believe GM did this (DRL) to comply with Canadian laws. Rather than make two different cars for the "North America" market, they made them all the same. Plus it easily allows cars bought in the US to comply with laws in Canada.

It appears that you have a 1999 model Suburban. You also have the manual. On online version is here: ... burban.pdf
Go to pages 6-62 and 6-63 of the manual (342 and 343 of the PDF). You will see that fuse 15 is for the DRL relay and the Fog lamps relay. If you don't have fog lamps, PULL THE FUSE! Problem solved. If you DO have fog lamps, do this trick.

Turn the key forward.
Make sure fog lamps are off.
Pull fuse 15 out and listen for click of the relay.
Put fuse back in and listen for click of the relay.
(Repeat as needed.)

Find relay and pull. Confirm headlights function normally. Confirm fog lights work normally.

Bob's your uncle.