I put new bulbs in. I've checked all fuses. The relay works, the other one for drl works. I've changed the headlight switch and still no low beams. Please someone help this is getting frustrating!

 

So, is it the high-beams are working as high beams or are they working in DRL mode? For the DRL function, the high beam filaments are run in series so that they are dimmed. That is why I ask.

Just to eliminate the obvious, you are turning on the headlights using the switch and not relying on the auto-lights feature. Right? What happens when you try to switch from hi to lo when the switch is in headlight mode? Do the headlights go out?

I'm attaching a schematic I made up in my attempt to understand this circuit in my 99 Blazer (below). Note that there are three relays, the headlight power relay (which must be working otherwise the headlights would not come on at all), the DRL relay that reroutes the current path to put the hi-beam filaments in series, and the head-light ground relay that provides grounding for the headlights when not in DRL mode. The states of these are determined by outputs from the body control module (BCM) so all of the connections for the inputs and outputs of the BCM must be good for the system to run correctly.

To test if the high-beams are being run in series or not, you can measure the voltage drop across one of them. If it is close to about 12V across the one, then that filament is in parallel with the other. If it is only about 6V, then it is in series with the other one and is in DRL mode.

Hope this helps.

 

If the relay clicks as it is supposed to then Im willing to bet your has the same issue that mine did. I had the exact same symptoms as you and started tracing wires.

First disconnect your battery negative terminal so you dont have any shorts while doing this work. Then remove the positive lead from the front of the underhood fuse block.
Then remove the 3 bolts holding the underhood fuseblock to the fender and flip it over. you should see 3 large plugs with a center bolt securing each of them. unscrew and remove the rear most large plug, then unclip the cover to reveal all of the wiring (it has 4 little tabs holding it).
Im willing to bet you will find one the the pins, (i believe #5) burned and black due to a bad connection and how much power goes through this tiny wire. i chose to uncrimp the wire from the pin, remove the burnt portion, strip back a good section and recrimp it to the terminal.

It will look sort of like this picture and you want to remove C1



as soon as you remove the big connector from the fuse block you may even be able to see which pin is burnt from the top. Mine was pretty bad and had even discolored the top of my plug.

 

The high beams do come on when I hit the switch. But I noticed when I kept switching the high beams on and off there were times when I would switch the high beams on and they wouldn't turn on. The high beam light in the dash that shows the high beams are on is on all the time now. Could it be a bad a turn signal switch? As far as the fuse block i will definitely try that tomorrow. Before i created this post the low beams wouldnt turn on at all. Then after, they were very dim. I got home from work and I checked again now they don't turn on again. Oh and going back to the high beams, when i switch on the high beams which bulbs are supposed to turn on? I thought it was the ones towards the middle but I don't have bulbs in them becuase I dropped them when i was doing a quick check of things. So i don't have bulbs for the high beams but when I switch the high beams on they still turn on. Will someone please clarify that as well.

 

If You have a filament bulbs and they glow, then it's the connectivity issue somewhere:
- relay
- lamp connector
- ground wire
Actually, Christine posted the diagram You need to follow. Get a voltmeter and look for the voltage drop.

 

I got it. Turned out to be the turn signal switch.

 

Good deal! I just want too say it is great when someone reports back once they fix a problem, it kinda makes all of us here as members cheer!!!

 

Congrats. How were you able to diagnosis it as the problem?