If the windshield wipers on your Mercury Grand Marquis are not doing their job properly, it becomes not only a question of aesthetics but a safety issue. Sometimes the windshield wipers can get misaligned and therefore become almost useless. No matter what the reason for this damage is, adjusting the windshield wipers on your car is a fairly simple task. With some basic tools and a few extra minutes, you can do the job as well as a professional mechanic can do it.
Prepare the Mercury Grand Marquis for working on the wipers. Turn the key in the ignition to the first setting, but do not turn on the engine. Turn the windshield wiper control to the slowest setting and let the wipers sweep a quarter or half of the way through a cycle
Turn off the ignition and remove the keys. This puts the arms of your windshield wipers in a parked position so you can easily access the bottom of their rubber blades.
Locate the adjusting nut at the base of each wiper arm. Remove the cap from the adjustment nut using a flat-head screwdriver. Do not forget to check to see if there are any leaves or other debris under the border of the hood where the windshield wipers rest. If there are, clean out the area.
Use a wrench to loosen the adjustment nuts if your windshield wipers are making a screeching sound when you use them in the rain.
Tighten the adjustment nuts if your wipers don't properly clear the rain off your windshield.
Start the car engine and spray some water on the windshield to see if the wipers are functioning properly. Adjust as necessary, following Step 4 and Step 5.
