HLF ??

DFD382

Member
May 25, 2010
224
SOUTH CAROLINA
Can someone please tell me if a 2011 gmc sierra is possitve or negative swictched. I am wanting to install a hlf in my truck..I am also wanting to install a tail light flasher as well any sugestion what tail light flasher to use...Thanks
 

cajunblitz

Member
May 20, 2010
1,217
Saint Martin Parish LA
DFD382 said:
Can someone please tell me if a 2011 gmc sierra is possitve or negative swictched. I am wanting to install a hlf in my truck..I am also wanting to install a tail light flasher as well any sugestion what tail light flasher to use...Thanks

They should be positive switched, but it's easy to test to see what they are. To check what type of headlights you have, follow these instructions:


With the vehicle off and the headlights off, test all of the leads going in to the headlight with a VOM or test light to ground. If you have power to any one or more of those leads while the vehicle is OFF, chances are you have a ground side switched system. This means that the bulb already has 12 volts to it, and the headlight switch system provides the grounds to the bulbs when activated.


For a ground switched system, with your test light connected to 12 volts, Have someone flick on the high beams while you probe, and if you get ground at one lead with the high beams switched on only, this is where you want to tie in (test the leads on both lights, imports usually have separate HB circuits). Make a note on each headlight which color is the high beam wire and wire your flasher according to the directions for whichever headlight switching you have.


With the vehicle off and the headlights OFF, if you have no power to any of the leads at the headlamps, chances are you have a positive side switched system and also tells you you already have ground to your bulbs, and the headlight switch system provides 12 volts positive to activate the bulbs..


For a positive switched system, with your test light connected to ground, Have someone flick on the high beams while you probe, and if you get 12 volts at one lead with the high beams switched on only, this is where you want to tie in (test the leads on both lights, imports usually have separate HB circuits). Make a note on each headlight which color is the high beam wire and wire your flasher according to the directions for whichever headlight switching you have.


I also recommend the SoundOff ETFBSSN-P for the tail light flasher.


Good luck.
 
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