I have a 2000 chevy blazer. My headlight daytime driving light and brights do not work manually or automatically. I have checked the fuses and relays and the are good.

run an auxiliary ground wire to verify, you might be surprised...

The headlight relay provides power to the dimmer relay, then power goes thru a fuse for each light for each circuit (4). The low beam fuses are in fuse block 2. The dimmer relay is controlled by the daytime running light module. The headlight and dimmer switches send signals to the DRL module. You may need a shop manual to troubleshoot the circuits.

there is a relay under the hood in the fuse/relay panel called drl, or daytime running lamps, that relay is most likely bad, a good way to tell is switch it with the high beam relay, if they come on you know thats it, if they dont, its the relay for the lowbeams, again switch it with the high beam relay and see.. either way i can tell you for sure one of those two are bad... but most of the time it is the daytime running lamps, or sometimes called driving lights relay. hope this helps you

The wiring for these headlights is complicated. The body control module (BCM) controls whether the headlights should be on or off depending on the ambient light sensor readings. Your headlight switch should override this if switched to on - if it doesn't do this, the headlight power relay may be faulty.
The daytime running lamps (DRLs) are also controlled by the BCM and a DRL relay, also controlled by readings from the ambient light sensor. If they will not come on, the DRL relay may be faulty.
However, the root cause could be a fuse, faulty light sensor, headlight switch, or BCM. I would start by checking the fuses and checking/replacing the two relays.

Check the fusible links under the hood. Also, double check the bulbs are in fact good. Lastly it could be a defective daytime running light relay.

If you have daytime running lights but when you turn on your regular headlight on they do not come on. Take the bottom of your steering column off (Two Small Screws) and look at the back of your turn/dimmer switch make sure that the light blue wire is connected. The wires will break off after years of raising and lowering your steering column.

car headlights have 2 filaments each, 1 for high beam and other one for low, if both headlights are off there might be problem with the wires or relays and fuse. Have this serviced by an authorized auto-electrician since electrical wirings for gasoline engined cars are quite delicate and requires urgent attention.

Hello there - I would suggest checking the fuse for your lights in the fuse box, and check under the hood for a fuse/relay box, and have the relay tested. If the fuses and relays are good, open the hood, and try to check the connection to the headlights and make sure they are securely connected. You also mentioned that when you push the headlights switch forward for brights, and turn on the night time head lights, and neither come on but the daytime lights do, makes me suspect the switch itself may be bad. I would first check the fuses and relays if any. Second, I would replace the bulbs (if replacable). Other than that, my last guess would be an electrical problem in the wiring somewhere. I hope this information helps you fix your lights. Thank you for your time and consideration in my suggestions/answers.

check the fuses for the lights or it might be the dimmer switch check at autozone

Not sure about a body control module, there is a pcm under the hood on the pass. side that controls most everything on these, however i would check your fuses for the seat, on the 00 models the headlights do stay on all the time while driving due to daytime running lights but if they stay on after you take the key out then id check the headlight switch or sensor on the pass side dash.