There are several kinds of relays. Some activate when grounded so de-activate when grounded. Or the power applied relays like the ones I have for my fog light setup. Got a PN for the relay handy? I have 100+ relays in my shop so I was going to cross reference.

 

More than you ever wanted to know about relays:
http://www.the12volt.com/relays/relays.asp

As far as part numbers go...

Radioshack - 40A relay - 275-001 - $8
Autozone - 40A relay - PL-RY2 - $6

Neither of those have a normally closed (pin 87A) contact, but that isn't necessary for the task at hand.

 

Wow the military needs to refer to this site for relays that was very thorough. When I went through BEC for my MOS training they skimmed through relays like they were nothing and relays are a vital source in the multi-million dollar aircraft I work on.

Goes to show that does not matter how much money you spend on training if you fail to find the most thorough and best teaching methods...your pissing that money away.

Thanks for the link I bookmarked it for further reading. As you never know everything.

 

On my '98 I just grounded the yellow wire on one side to the chassis and it works on both headlights. Seems to work fine, the wire doesn't get hot or anything (as would be expected if the wire was sinking enough current for both lights).

 

I wonder why the Blazer's don't have relays in the fuse box? On the fullsize trucks (I can't remember the numbers, probably pin 87A) the guys run a diode between "turn on" pins on the highbeam relay and the lowbeam relay.

Quick read
the wiring diagram for my relays witn a 1n4004 diode


I no longer have a Blazer to go off of, but can someone confirm that there aren't any relays present under the hood for the headlights?

 

There is one for the headlights under the hood. Do you need a picture Oktain?

 

Only one relay labelled hdlp? or headlamps or w/e? hmmm, then you guys are stuck cutting into the harness, I was hoping there would be a separate relay for high and low beam.

Notice in the diagram I provided the HDLP-HI and HDLP-LOW relays. That's for a fullsize GM truck 03+.

 

There are three relays in the non-zr2 98+ trucks. It is not as simple as the method you mentioned.

 

Which is why I probably will not have this mod done.

So to date only method for this is cutting wiring harness?

 

The way I'm going to do mine is with a relay on the yellow wire to ground it so I have control over when all 4 are on or not. This way I'll keep the DRL's & be able to have high beams normal or along with the low beams at my choice. Flick a switch in the cab & low current wires trip the relay as to ground the yellow wire. - presto majico quad beams!

Switch off = open circuit, all headlights are normal
Switch on = quad beams

& with the 5000K HID's I have to go in the high beams - WOW lots of light on the highway along with the 8000K lows in projectors while pulling the boat back from the lake at 1AM. Just flick the switch when there are oncoming motorists & it's back to just lows.

This might also help Mykeboy01 in his dilemma with his low beams on at full power