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High/low Headlight System

rngr746

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rngr746 Enthusiast

rngr746

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I have a 2007 GMC Sierra and am looking for information on how to wire up the headlights so that when the high beams are switched on the low beams stay on as well. Ideally, I'm looking for a simple step-by-step process using just a relay.

zeven13 Enthusiast

zeven13

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Search.

 

I have a 2007 GMC Sierra and am looking for information on how to wire up the headlights so that when the high beams are switched on the low beams stay on as well. Ideally, I'm looking for a simple step-by-step process using just a relay.
MS3DALE Senior Enthusiast

MS3DALE

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If your '07 is a GMT900 you don't have to do anything,The low-beams already stay on with the high-beams.

lsuguy Senior Enthusiast

lsuguy

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It's for sure on this site. Again is it a gmt900 ( Newer body style) or gmt800 (not as new body style)?

rngr746 Enthusiast

rngr746

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My truck is an 07 Sierra Classic W/T. Hope this helps. I was not aware the body styles made a difference. Thank you for your patience as I learn more...!

redvett Senior Enthusiast

redvett

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1999 to 2007 is GMT800 2007 & later is a GMT900. Forget the NBS,NNBS its not an accurate designator.

 

My truck is an 07 Sierra Classic W/T. Hope this helps. I was not aware the body styles made a difference. Thank you for your patience as I learn more...!
rngr746 Enthusiast

rngr746

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Thanks for all the assistance and patience with me during this process. The low beam lights now stay on when I activate the high beams. What I did was to use a 1n4004 diode. I kept the white strip towards the high beam #85 pin relay and ran the other side to the #85 pin on the low beam relay. Everythings workd fine and it sure helps tremendously with the night driving I have to do on rural county roads.

Just as an FYI, I tried the same set up with a 30Amp relay and kept blowing the left low beam fuse.

ike-sierra Enthusiast

ike-sierra

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This mod seeems very easy just 1 stupid question. Where is the connector(s) where you put the diodes? under the dash, side fuse panel, or under the hood fuse box? Any pics would help too thanks.

rngr746 Enthusiast

rngr746

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There is no such thing as stupid question!! I forgot to include some information. I used the under the hood fuse box. Refer to diagram on the underside of the fuse box lid. By pulling the highbeam relay, I was able to insert the wire from the diode (white stripe facing this relay) into the #85 pin "socket" for the high beams and then to the #85 pin for the low beams. Hope this helps! I'm not much of a computer type so am unable to post any photos.

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