Which parts fail
Components named in complaints (headlights, tail lights, turn signals, interior lights).
Mileage when the problem started
Owner reports
Selected complaints filed with NHTSA by 1999 Mercury Grand Marquis owners, lightly cleaned up (personal details are redacted by NHTSA).
Intake manifold failed (burned and disintegrated in the area of the thermostat ) and had to be replaced at considerable expense . Presently the speedometer fails intermittently dropping to zero at random moments. Most importantly the lights cut out intermittently usually when the heat is on and on longer trips. Also, most times it has happened when it has been raining and colder. Drove upwards of 40 miles with the headlights cutting out intermittently in the rain and cold, problem has continued to recur but seems to be related possibly to having the heat on. I believe the lighting control module is located near a heating outlet and May be suffering a failure as a result but this is just speculation. Also, previously when I had pulled into a rest area for awhile, after cooling down, the problem went away for a little while then resumed after about ten miles with the heat on. …
We own three Mercury Grand Marquis, love the cars however all three( 2000, 1999 and second 1999 all intemitantly loose headlights when high beams are on. If I quickly go to low beams I can see again...its like they are overheating with the amp draw of high beams and circuit breaks. This is way too common to be OK. It dangerous especially if one gets rattled with complete darkness at night and high speed. Bumps also seam to slightly affect it sometimes. This happens any time the gray 99 has high beams on for about 45mins. Only 10-15mins on blue 1999 and 2000 not as frequent yet but only has about 75K miles, where as the 1999 are 150-210 respectively. Started 5 years ago on my first and I just did not use high beam since I purchase second 1999 to replace first and had title issues so bought the 3rd 2000 and found they all have the same flaw!! My cell [redacted].
The 3/4 key on the driver side door randomly quit working. Every other button still works, and when any button other than the 3/4 key is pressed, the keypad lights up. My key code includes the 3/4 key though, so I cannot use this keypad to unlock my vehicle or trunk. However the keypad lights up on its own, which causes my exterior and interior lights to illuminate. These lights cycle on for about 15 seconds and turn off for about 30 seconds. I had to remove my interior dome lights because they would drain the battery. If I am parking for an extended period of time, I have to disconnect my battery so the lights will not drain it. The Ford dealer checked for a recall on the lcm, but the recall does not affect the 1999 model.
Tl* the contact owns a 1999 Mercury Grand Marquis. While driving approximately 40-45 MPH, the headlights stopped functioning independently. The failure happened without warning. The vehicle was taken to an independent mechanic who diagnosed that the control module behind the dashboard malfunctioned and needed to be replaced. The vehicle was not repaired due to parts no longer being manufactured. The manufacturer was not made aware of the issue. The approximate failure mileage was 140,000.
Tl* the contact owns a 1999 Mercury Grand Marquis. The contact stated that while driving at approximately 35 MPH, the low beam headlights failed intermittently. The contact mentioned that the headlights would activate and deactivate independently. The vehicle was taken to the dealer where it was diagnosed that the control module was damaged and needed replacement. The manufacturer was notified of the failure. The vehicle was not repaired. The approximate mileage was 133,596.
Tl* the contact owns a 1999 Mercury Grand Marquis. While driving approximately 45 MPH, the headlights suddenly began to flicker off and on. The vehicle was taken to an independent mechanic who diagnosed that the light control module was faulty and needed to be replaced. The vehicle was not repaired. The manufacturer was notified of the failure, but no assistance was offered. The local dealer was not notified. The failure mileage was 134,000.
Tl* the contact owns a 1999 Mercury Grand Marquis. While driving 65 MPH, the headlights failed to operate intermittently. The contact stated that the vehicle exhibited the same symptoms as listed in NHTSA campaign number: 15V861000 (exterior lighting). The vehicle was not taken to a dealer to be diagnosed or repaired. The manufacturer was notified and did not assist. The failure mileage was approximately 160,000.
My headlights, hazards, and turn signals all just randomly went out while driving. They have not come back on since. After reading forums I believe it to be the lcm but my year model is not included in the recall. I believe this issue dates back farther than 2000 and Ford should step up and recall more of these lcm components.
Vehicle was parked. I went to turn my headlights on. No headlights, turn signals, dash lights, hazard flashers or dome light. The 2003-2005 models were recalled for this same thing with the lcm failing. Please look into this as this is a serious safety issue.
Problem: intermittent headlight failure while driving at night with 1999 (1998 year of manufacture) Mercury Grand Marquis. Lights go off for as long as 2-3 seconds and come back on again for a second or two, then go off again, then back on again, etc--and only occurs after the vehicle has been driven for 20-30 minutes. This happened once before, about two years ago, with this very same vehicle and I solved the problem by replacing the headlight switch on the dash. Apparently there is no headlight-related recall* for this particular Mercury and the cost to dig deeper into the cause of this problem by the Mercury dealership will be therefore at my expense. The cheapest repair cost scenario at the dealership is over $300. …
Headlight complaints in other Grand Marquis years
Frequently asked questions
How common are headlight problems on the 1999 Mercury Grand Marquis?
NHTSA has 21 complaints about the lights of the 1999 Mercury Grand Marquis, 13% of the model year's 164 complaints. The component named most often is headlights (7 mentions).
Is there a recall for 1999 Mercury Grand Marquis headlight problems?
No. NHTSA lists no lights recall for the 1999 Mercury Grand Marquis, though it has 3 recalls for other components. If the problem is widespread, a repair may still be covered by an extended warranty or a manufacturer service bulletin — ask a dealer.
At what mileage do 1999 Mercury Grand Marquis headlight problems start?
Half of the complaints with a recorded mileage happened before about 140,000 miles.
Source: U.S. National Highway Traffic Safety Administration (NHTSA) — owner complaints through October 20, 2026, recalls and defect investigations; fuel economy from the EPA. Complaints are unverified reports and are not proof of a defect. How we rate model years.