Yes you have a relay that powers the headlights now, but the wires are small. By adding a relay rite off of the battery, this supplies the headlights tire from the battery. And then you use a bigger wire to supply the headlights. This makes a HUGE difference in how bright the headlights are. So much, that after I did the 4 high beam headlight mod on my truck, I added another relay form the low beams so that they would be feed from the battery. I used the wire that supplies the low beams, and used this wire to switch the relay on, and now the lights are feed rite off of the battery. I used a #10 wire to feed my headlights.

 

Brad,

First, you never want to run full amperage through a light switch, that is why there are relays. The relay is a glorified fuse that takes the blunt of the current load.

Voltage is what makes lights brighter, not amperage, not 10 gauge wires, just voltage. Having too much current draw will dim down the lights. That is why I'm asking the next question.

What is the "amperage" of the lights??? If you don't know, then I need all the resistance values of each bulb that is going to be powered for me to get the amperage consumption.

Another thing Kenny hasn't mentioned, did you notice the "amperage values" on the relays??? 99.999% of the people who use a relay system, ignore what all the technical crap means. If people knew what they were doing, they would know what all the chit means.

In this above picture, it tells me the relay is "normally open". That terminal 86 is ground, terminal 85 is switched power. That terminal 30 should be the voltage source for the accessory and terminal 87 is the accessory source that switch power needs to be applied.

I agree with Kenny on the 10 gauge wires, because if a 10 amp load is switched on, it's normal to have a "voltage" and "amperage" spikes for a few milliseconds that can almost reach 30 amps. You never want to over load any relay. If you want those relays to last, you run more like 30 to 40% amperage capacity to keep the relay cool.

God, ..I'd love to re-wire Kenny's relays in such a fashion they would look like a factory installation. No electrical tape, just the female electrical connector for the relay and my collection of convolute (plastic tubing in the picture) and harness wrap. There would be no solderless connectors.

 

There are several post on here about the 4 high headlight mod. The issue on a lot of trucks , and cars, is that the manufacturer uses a small wire that does a poor job of carrying the amprage needed for bright headlights. When you replace those OE wires, and come directly off of the battery, the supply wire run is very short, and the amprage flows a lot better. Electricity flows like water. A small hose will not let a lot of water through. Use a bigger hose at the source, and you will have a lot better flow. Same thing for amprage flow.

God, ..I'd love to re-wire Kenny's relays in such a fashion they would look like a factory installation. No electrical tape, just the female electrical connector for the relay and my collection of convolute (plastic tubing in the picture) and harness wrap. There would be no solderless connectors.

LOL as for my crappy job,, well I guess I am a little laze. The battery covers all of this. so none of it shows. Also I am a bit of a tightwad. I could have bought a kit , but I just made my own. The relays are taped because they are not water proof. All of my tie in connections are soldered. Here is a pic with the battery in place. The red wire on the side of the battery, is the supply wire for my headlights.

 

Oh one more thing. You need to fuse any new wiring that you add.

 

And Kenny, just to add a little to your very clear water flow comparison; the relay acts like a late gate valve that is electrically operated.

 

the 4 high and low mod is one of the best mods I've done to my truck.

I'll see if I can find my thread for you although you may have allready read it...

Al

 

https://m.ebay.ca/itm/302121113140?rmvSB=true&ul_ref=http://rover.ebay.com/rover/1/706-53473-19255-0/1?type=4&campId=5337560597&toolId=10001&customId=j8fyfaxqmv0102xb00005&mpre=http%3A%2F%2Fwww.ebay.ca%2Fitm%2F302121113140&srcrot=706-53473-19255-0&rvr_id=1328601156504&_mwBanner=1&ul_noapp=true

iv delt with this seller and used this kit once, great product at a great price and a great seller. it comes with detailed instructions, just remember to throw the blue plastic wire taps in the trash and solder and shrink wrap everything. there is waterproof automotive double walled shrinkwrap, I wish I knew about them when I modded my lights, get em and use them, they are awesome!

heres a pic of the relay harness and instructions, I didn't get a pic of the instructions themselves. just to note the pic says for 88-98. however this applies to all gmt400's which your truck is. the last gmt400's were built in 2000, tahoes or yukons or something...

cheers! Al

 

F! this site is getting to slow on my phone with all the new adds its really starting to piss me off! I just edited my post above and its gone.... GRRRR!

anyways heres the synopsis... get new or restore your old lenses, I have spyder glass lenses but originally restored my old ones with a 3m drill powered kit, worked like a charm but one of my lights was actually broken.

the other thing is perform a proper headlight alignment with a half a tank of gas in er.

proper headlight alignment procedure...

In my Haynes manual under electrical, its pretty simple to do.

Before doing a headlight alignment make sure you have half a tank of gas and not a heavy load in the truck.

Basically park the truck inches from a wall on level ground.

Take masking tape and mark the center of each low beam bulb then back the truck up straight so that the lenses are 25' away from the wall.

Take masking tape and run a line from one of your previous marks to the other. Then place an X 2" down and in toward the center from your original mark. And mark the very center with tape as well.

Now you aim the low beams so that the most intensity is right on the X.

I placed plywood over the lense I wasnt working on to make things a bit easier. Once you get it close take it for a drive and see if it lights the road properly.

I had a dark spot on the passenger side that I wasn't pleased with so I brought the truck home and made an adjustment which wasnt quite right so I did it again and it was perfect.

Of course the haynes manual says to take it to a shop as soon as possible for a proper alignment but nobody flashed me and I'm very happy with them!

Heres a pic...

Al

 

some of my threads...

gmt400 headlight mods

http://www.gmtruckclub.com/forum/threads/gmt400-headlight-mods.1127114/

Spyder glass lenses

http://www.gmtruckclub.com/forum/threads/spyder-glass-lenses.1127154/

adding fog lights to gmt400

http://www.gmtruckclub.com/forum/threads/adding-fog-lights-to-gmt400.1124802/


Headlight Restoration


http://www.gmtruckclub.com/forum/threads/headlight-restoration.987850/

I thought I had a couple more but cant find them n I'm out... have a good one all!


Al

 

Grate job Al. I was looking for the thread, and couldn't find it.

 

Kenny can you show/tell me where the relay is? I've read some models have no relay, some have one for both hi and low and some have two relays, one for each hi and low.

 

For the 4 high beam mod, you add 1 relay. You tie in at the headlight bright wire, and use this as the switch wire to activate the relay. The other side of that relay (the lead side ) comes off of the battery, and powers the low beams when the highbrams are switched on. Then I added a second relay, just for the lowbeams. For this I cut the supply wire from the headlight switch (next to the battery) and used it as my switch wire for the second relay. This is now also supply by a larger wire from the battery. When doing the low beams, you need to pull the fuse from the DRLs. There are some good videos on doing the 4 high mod on YouTube. If you need something else, just ask

 

Got it, thanks. My question above was about the stock relay. Do you know where it is located?

 

Thanks Kenny! mine are wired exactly the same thanks to you man! CHEERS!

Brad, my 97 burb dosent seem to have a stock relay for the headlights unless its not in either of the fuse boxes. I would assume yours is the same.

I snapped a couple pics...

fuse box.... no relay just a big fuse.

4 High n low relays...

 

Thanks Kenny! mine are wired exactly the same thanks to you man! CHEERS!

Brad, my 97 burb dosent seem to have a stock relay for the headlights unless its not in either of the fuse boxes. I would assume yours is the same.

I snapped a couple pics...

fuse box.... no relay just a big fuse.
View attachment 108097

4 High n low relays...
View attachment 108105
View attachment 108113

The OE headlight relay is in the fuse box under the hood I think. I know there is one, but the OE wiring is just to small. Your looks grate Al. Just like mine, like you said. I hope all is well with your and yours.

 

Yeah, I had read that mine may not have a relay at all and just uses the switch but then Rick's reply made it sound like there's always a relay.

 

Here's a thought. Let's say I install a relay just for the low beams to make them brighter. Simple right, just use the existing low beam wire as the trigger for the relay and then the lows would be powered right from the battery through the relay potentially making them brighter. I think I just described a common mod. Now, If I connect a diode from the high beam wire to the low beam trigger it would turn on my low beams any time the highs were on but the diode would block the low from going to the high wire. If this works then I only need one relay (and a diode) to make both mods. Both mods meaning brighter lows and 4 hi. As a note, the existing low beam wire would be cut and go directly to the relay as a trigger. It would not continue to the low beams with just a tap going to the lows. Hope this makes sense. Probably should draw it and post a pic. Can anyone correct me if I'm wrong?

 

I found some schematics to avoid all the confusion what I might of said.

Aftermarket lights "will need" a minimum 30 amp relays for each level of lighting.

Some factory lighting systems go through the power distribution center (PDC), some through the Daytime Running Light (DRL) module or the Body Control Module (BCM). Relay hunting is an adventure!

Now to the schematics for study:

 

There is no need for a diode. Just tie into the supply for the highbeams. Thats all there is to it. This is your switch wire for the 4 high mod. When you are on low beams, there is no power to the high beams so the relay is off. It only switches on when you go to high beams. On the lowbeams, you cut the supply wire and use it to switch on the second relay. The DRLs will switch on this relay, so you need to disable the DRLs. You are on the rite track with your thinking on the low beam relay. Keep in mind that a relay is just a switch that is controlled by an electromagnet. When the rely is switched on is the only time power can flow through it. When it is off electricity can not flow. This is why you do not need a diode. Erick the car guy is the bomb, check out this video

 

Diodes are use for voltage spikes, ...and to protect electronic circuits that can't handle voltage spikes. Some relays have the diode built in as not to leave a voltage spike signature. Kenny's relays do not have the diode option.

 

The diode Brad mentioned is used for blocking. Yes every relay winding should have them to keep the relay winding from acting like an ignition coil but that's not why he wanted to use it.

Yes Brad the diode will work fine. You might want to read through this thread for suggestions.

http://www.gmtruckclub.com/forum/threads/diode-conversion-for-all-lights-on-high-beams.52682/

Ted

 

A diode is a one way directional valve use in electrical circuitry.

 

I just thought maybe I could get away with one relay and a diode to do both mods instead of using two relays.

 

It all comes down to "amperage load", ...and you don't need a diode unless some electronics are in the light circuit. If and when you get a diode, measure the mega resistance, then swap the leads and watch no resistance. A diode is a one way electron flow valve.

If your more than 15 amps for each lamp group, use the above 2 relay diagrams.

 

When Brads diode conducts it will only pass the current needed to pull in the relay. A 1n4001 will do it, although I only use 1n4005 for peace of mind. He is going to put the diode between high beam and the relay pin that his low beam signal trigger is on. When high beams are on the diode will trigger the low beam relay. When low beams are on the diode will block the low beam trigger from getting to the high beams. He will need another relay to supply the high beams.

Edit: Just to be clear two relays and 1 diode, Brad.

Ted

 

Ted, can you explain why I would need two relays? Couldn't the low and high trigger the same relay? Oh I get what you're saying but I wouldn't cut the high beam wire. Just tap into it. The highs could continue to be powered as they are now. I guess the high beam wire would be carrying more current because it would have to source current to the highbeams and also current to energize the low relay.

 

Ted, can you explain why I would need two relays? Couldn't the low and high trigger the same relay?

First off relays are dirt cheap. Less than $5 each. Second, the reason you need 2 is if not, you'll have 4 headlights on all of the time. When you hit the highs, this will trigger the low beams. When you hit the lows, the relay will back feed and triger the highs, because you ha ve both high and low beams tied together. 2 relays is what you need to do this mod, just drive around with dim low beams untill you triger the highs with just one relay and, once you see how much brighter the lows are on a relay, you will gladly spend the extra $5 for another relay. I did, when I told Al, he did, and I think Ted did too. This is the correct way to do the mod. My truck has had this mod for about 3 years.

 

Brad,

It all depends on amperage load on the given accessory. You have to figure in the peak power spike when the accessory is first turned on and the steady power the accessory gives the relay.

On one of my older C3 Corvettes I have 2 "aircraft landing lights" installed as high beams. They are each 100 watts of undiffused direct beamed light. Knowing I'm running at 14 volts, my amperage 14.285 amps for the pair. With that bit of information, I run one 30 amp relay without issue.

If I were to run a 15 amp relay, the relay would kick out within 5 minutes because of current overheat issues. Higher the amperage rating, lower the operational heat output.