Why isn't HVAC on 2005 buick lacrosse not working?

SOURCE: Air conditioner/heater blower fan on 1997 Buick

it will be hard to diagnose with out having my hands on it but try this.

this vehicle is known for blower motor resistor failure.

under the dash on the passenger side next to the blower motor there is a resistor attatched to the blower motor case it will have a single plug with 5 or 6 wires in it, they are normally within a couple of inches of the blower motor, remove this resistor and look at closely for any signs of burning this is a common problem, you can buy one at any parts house, do not operate the motor with the resistor removed from its mounting hole or you will damage it.

if the resistor looks good than purchase you a test light and drop me a line and i will explain how to test the entire system its not hard to do.

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SOURCE: lowbeams headlamp won,t work on 2005 buick

Start simple. Investigate your fuses, since it is unlikely, but not unheard of, for both low beams to fail simultaneously.

Do you know where your fuses are?

SOURCE: how to install/change complete headlight assembly

Buick Lacrosse - The bright light fitting is the same as the dim so take it apart first to see how the cover screws off/on and the light comes out. Both the cover and the bulb are removed by a standard twist to the counterclockwise and replaced by a twist to the clockwise. Now to the dim light. You have to release the entire light assembly before you can remove the screw-on cover to reach the light. On the rear edge of the light unit closest to the engine is a white locking tab. Pull that tab up just to the point where it releases…pull too far and it locks again. Next, locate the other locking bracket which is a metal bracket in the center-rear of the light assembly. This bracket is held down by a screw. Remove the screw with a 10mm wrench. Lift the bracket just like you did the white bracket. You should now be able to pull (or pry) the entire light unit forward a little. Depending on the size of your hands this might be enough. If not, then you need to release the plastic bumper assembly to give you a little more space. This is done by removing two expansion locking pins, one that holds the little plastic strip down between the bright and dim lights and one that is located inside a rubber bumper on the engine side of the light unit. To remove these locking pins, pull or pry up the little tab in the center of the pin just like you were pulling a nail by the head. That should give you more space.

SOURCE: 2007 Buick Lacrosse low beam headlights both went

The relay under the hood may have gone out. We had the same problem on our 2007 Buick LaCrosse CX. The bulbs were fine, high beams worked, all turn signals and everything except the low beams turned on. Turns out the relay had gone bad.