The GMC Sierra 1500 HD headlight assembly is built to keep you safe from dark tunnels and the night sky. In time however, batteries weaken, moisture builds up inside, and electronics falter. This of course leads to the headlight assembly not being able to function properly, which could lead to a disastrous road accident if unprevented. If you are starting to have issues regarding your GMC Sierra 1500 HD headlight assembly, then you better start doing some troubleshooting. Listed below are some of the common problems associated with the part, as well as their causes and some quick solutions:
If your headlight assembly ceased to function, then there are two things to check: the bulbs and the wirings. Burnt out bulbs are usually common occurrences, especially if you have been using them for quite some time. If this is the case, then it is as easy as unscrewing the defective bulbs and putting on a new one. As for the wirings, it could range from corroded wires, blown fuses, or broken switches. Be sure to check carefully so that you will not misdiagnose the problem.
When you experience your headlight assembly suddenly going dim, or flicker on and off, but the bulbs and wires are working fine, then go look at your vehicle's battery. Use a voltmeter to measure the battery's strength and whether it is able to give out enough power to activate the lights properly. Another possible cause could be the alternator. A defective one could weaken the battery's charge. This in turn would result in it slowly losing its power. Because it can't recover, it will eventually power out and kill the lights. Do not simply ignore this problem, as it could cause a vehicular accident, especially during the night.
Place your car inside your garage and turn off the lights. Turn on your headlight assembly and measure whether or not it is aiming at the correct angle. If the alignment is wrong, then adjust the headlight lenses. Correct aim is important to prevent your vehicle from blinding anyone in front of you.