Mercury Grand Marquis Parts And Mercury Grand Marquis Accessories
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Mercury Grand Marquis: Headlight Problems and Fixes
The earlier versions of the Mercury Grand Marquis sported an old-fashioned automotive design with their heavy body-on-frame construction and solid rear axle. This full-size rear-wheel drive luxury sedan eventually caught up with the advancing times with its lighter unibody structure and fully independent suspension. Although it has its shortcomings when it comes to ride quality and vehicle handling, it\'s rather valued for its spacious cabin and quiet ride. If what keeps you from taking your Marquis out for a spin is impaired visibility due to faulty headlights, here\'s an easy way to figure out the problems and solutions.
Only one headlight works
If one of the headlights won\'t work, the bulb has probably burned out. Bulbs typically last 5 to 6 years based on how they\'re used. Vehicles that are used for night time driving and suffer from vibrations due to driving on rough roads would have bulbs that could fail much faster. As the burned-out bulb is replaced, the electrical connector should also be checked for corrosion, damage, and looseness.
Both headlights don\'t work
With both headlights failing to work, you have to check for a broken headlight relay, module, fuse, switch, or wiring if the problem doesn\'t involve burned out bulbs and appear to be a case of having no voltage or power to the headlights. The first thing to check would have to be the main fuse for the headlight circuit to see if it\'s blown and needs a new one. A blown fuse indicates a shorted headlight circuit, which needs to be traced and fixed. If, after inspection, you found out that you don\'t have a bad fuse, you should check whether or not there\'s power at the fuse using a volt meter or a 12-volt test light. Lack of power at the fuse could mean that there\'s a wiring fault in the fuse block or somewhere between the block and the battery. If there\'s power, the next thing you have to check would be the relay or control module. A bit of investigation would reveal whether or not you have to replace the relay or module. If the module is receiving power while the switch is on and the headlights still won\'t work, the module should be replaced. You probably have a bad relay if something inside it rattles when it\'s pulled out and shaken a bit. You can blame it on a damaged headlight switch if the relay or module isn\'t getting power while the switch is on. The dimmer switch is malfunctioning if the headlights work only on low or high beam.
If the headlights appear dim or the brightness fluctuates when the engine is revved, the problem is most probably with the charging system. It could be a case of a bad alternator or a slipping drive belt. The charging voltage while the engine is idling should be checked to verify the cause. When headlights fail to illuminate the road well, the headlights could be dirty, there could be fog inside the lens cover due to moisture, the plastic headlight cover is discolored, or the lights aren\'t aimed the right way.