2007 chevy trail blazer low beam lights wont work.

check the headlight relays ,
Check for possible faulty light stalk switch also. Dash lights may fail with this possible cause.
Check fuses

ok if you run a power wire to the positive on battery does it go?
if so its a plug or cable issue. if not make an earth wire for the earth side of light and try the power again. if it goes you have a bad earth.

Could be the dimmer switch.

Hello Linda! Replacing the HDM relay for the low beams will not trigger any of these problems. If the blower isn't working, you probably need to get a new blower motor resistor (for manual controls) or blower motor module (looks the same) for automatic climate control. To access, need to remove the plastic kick panel near your feet on passenger side. After removed, look up you'll see the resistor, it's about 4" long with 2 small screws in it. You'll also need to drop the glovebox door to remove the connector from the resistor to the motor. Suggestion- buy a pig tail for the resistor also, these tend to melt. Very common problem. The ABS dash could be a bad wheel hub assembly or a hub starting to go bad.

I work for a chevy dealer I will look into the problem and get back to you.

I believe in a Chevrolet you push the left stalk (turn signal stalk) foward for high beam and back for low. If you have the lights on low beam and pull the stalk back, you'll "flash" your high beams.

Are these automatic headlights?

check the low / hi beam switch

If they work at night leave it alone
(Those ******* "Driving Lights" cost you gasoline to run.)

check the head lamp dimmer swicht