Did the mod. Very surprised at how thin the wire gauge is on the Lighting Harness. There must be a lot of Voltage drop to the bulbs.
Brought the wire in and Grounded it to the Passenger side Horn mounting bolt.

Question: if the car was equiped with DRL, would the lights come on when the car is in Gear only or would the lights come on as soon as you start it? Looking at the first Post got me wondering what the Stock lighting does without the Mod.

 

Did this mod and my headlights went out all together. No fuses. Relays clicking. What can be shorted out

 

My thought on the quad beam mod... only use the factory wiring as a trigger for two relays that are fed straight from the battery. This way there is virtually no voltage loss from battery to the bulbs. I have not had my Jimmy long enough to do it yet (less than 3 weeks) but when I did it to my 86 mustang I measured voltage at idle, stock wiring at 11.7. But once I put in relays and power straight from the battery voltage at the bulbs at idle was 14.3, exactly what my alternator put out. The light output was phenomenal compared to stock.

 

Very valid point as far as voltage drop and brightness. But Many people can live with the increase of justy having all four bulbs on at High Beam.

I designed a Relay Board for my other car. It's literally a plug and play for the 9004 bulb setup in my other car. Teh board is in-line with teh Bulb harness and teh bulb. As you say, the headlight switch JUST triggers the relays which gets it's power direct from the battery via a 10 gage wire.
13.7 volts at the bulbs makes a big difference over 11.5V.


87yellow subi: What year Blazer, and are you sure you got the Yellow wire in the Harness to the headlights? You don't cut that yellow wire, you just ground it.

see here why pay $50+ when you can do this? its almost free - Zr2USA.com

 

True, but I hardly ever get to use my Highbeams, as there is a lot of traffic around here, and there seems to always be someone infront of me or coming at me... I also wonder about the heat generated by both bulbs on at the same time... granted I have a 95 so i only have one bulb, but in the past I have seen some headlight housings melt due to the lights being wired in this fashion... I would rather send true 13+volts to th bulb, or retrofit true HID projectors in like I did to my 02 Mustang GT. to bad i cant find any clear lens lights for my Jimmy...

 

99 blazer 4x4. Yeah, I know. I spliced into the yellow wire [I didn't cut it. But now my headlights don't work at all. I gues its about time I just put everything back to normal and take the piece of junk to the dealership and tell them to fix it. I'm stumped on this one

 

Odd. I did the mod to a '99. I jumped out the Passenger side but it doesn't matter.
I can't say what you have going on there. Mine went seamlessly.