Which parts fail
Components named in complaints (battery, alternator, wiring, ignition, instrument cluster, infotainment).
Mileage when the problem started
Owner reports
Selected complaints filed with NHTSA by 2008 Mercury Mountaineer owners, lightly cleaned up (personal details are redacted by NHTSA).
While driving on a long trip, without warning, the memory seats change seat setting and went back fully as if I shut the vehicle off, this happened several times while I was driving without my assistance. I finally realized that when I touched the keys in the ignition, the seat went back to its original setting. When this occurred I was unable to reach brake and accelerator pedals which could have caused a fatal accident to occur. If this happened at a time that I needed to apply the brakes, I would not be able to and there would have been no way for me to stop. I took my vehicle to an authorized dealer who replaced the ignition. On 6/6/2012 the same thing happened again (mileage 60774), this time I struck the car in front of me, it was a good thing it happened while I was in traffic, and neither vehicle sustained damage. …
While driving down the road, the seat will suddenly move backwards to the "open door" position, as though the key had been pulled out of the ignition. This creates a very dangerous situation, especially for people with short legs, as one can no longer reach the gas pedal or brake. Slightly "wiggling" the key or ignition switch will usually get the seat to move back to the preset driving position. When this happens, the interior lights also go on, and turn off when the seat moves back into position. This seems to happen at all different speeds, and it seems most events happen after the car hits a bump, but not always. There have been times when it just seems to happen without anything to set it off. It also can happen when the vehicle is first started up, or just as you start to shut the vehicle off. It is absolutely ridiculous that repair of this condition is not a recall item. …
Tl contact owns a 2008 Mercury Mountaineer. When the contact started the ignition, the dome light illuminated unexpectedly. The failure occurred intermittently and the dome light would not dim automatically. Whenever the vehicle was in operation, the dome light would illuminate and the front driver's easy-access seat retracted without warning. The vehicle was taken to an authorized dealer for diagnostic testing and they stated that the failure was related to the to keyless entry module. The vehicle was repaired under the service warranty; however, it was insufficient. On a separate occasion, the failure recurred. The contact was involved in a minor crash, which May have been caused by the vehicle's malfunctions. There were no injuries. The vehicle is in the process of being taken back to the authorized dealer for repair. The failure mileage was 16,000 and current mileage was 17,500.
Defective ignition. When driving, if you bump the key (or attached keychain), all interior lights will come on, and the drivers seat will retract all the way back into the "easy entry/exit" position, making it impossible for a shorter person to reach the brake or gas pedal. Sometimes during this event, the car will stall. This is very dangerous, and the internet is full of people having this identical issue. Why hasn't this been recalled yet?!? People are paying for a new ignition tumbler, but before long it starts happening to the replacement tumbler as well. Http://www.carcomplaints.com/Mercury/Mountaineer/2008/accessories-interior/seats.shtml
At 28000 miles the transmission started shifting erratic, the dealer reprogrammed the ECM and covered up the problem until the warrant ended and the battery failed at which time the car reverted back to default and continued to buck and jerk until the car reached highway speed. This continued until the transmission finally failed during operation on the highway on 3/5/20. The ABS module just failed during low speed operation for no apparent reason. Also the car indicated that there is an electrical problem even though all electrical components are in good operational condition. This error comes and goes constantly at any given time.
Tl* the contact owns a 2008 Mercury Mountaineer. The contact stated that the instrument panel lighting system was inoperable. The vehicle was taken to an independent mechanic who diagnosed the vehicle however, was unable to determine the cause of the failure. The instrument panel lights were replaced however, the failure recurred. The vehicle then was taken to maritime Ford (1305 franklin st, manitowoc, wi 54220) where the vehicle was diagnosed and it was determined that the dimmer switch needed to be placed. The manufacturer was made aware of the failure. The failure mileage was approximately 120,000.
While driving the vehicle, the seat suddenly went all the way back and the interior lights came on. This has happened several times since then, we finally figured out it was the ignition, with the car acting like the key just got put in the ignition or just pulled out, and the seat moving all the way back for easier ingress/egress and the courtesy lights coming on. Since I am only 5 foot 4 inches, when the seat moves back I can no longer reach the petals, a very dangerous situation while driving.
While driving the driver seat automatically goes back and the interior light comes on...this is gonna cause an accident cuz when the seat goes back the memory key for the seat position doesnt work until u turn the ignition off and back on again, once the seat goes back I cant reach the break or peddle. This is dangerous situation and isee im not the only one having this issue? It happens several times a day..soemtime when u first start it but mostly while driving down the road
After approximately 90,000 miles the dome lights turned on and automatic seats move back while driving. This issue persists and often occurs several times. There are several complaints of this issue found online. It is not due to a heavy key chain as I only have the fob and key attacked. This is a safety issue as the seats pull the driver away from the pedals and steering wheel. Investigate! Recall!
While driving the vehicle the interior light turns on and the seat moves back into the park position. This is a safety issue as it is difficult to reach the pedal/brake and it happens without notice. There is no rhyme or reason to this problem. I have seen multiple posts regarding this issue and don't see how it cannot be a recall for safety reasons
Electrical complaints in other Mountaineer years
Frequently asked questions
How common are electrical problems on the 2008 Mercury Mountaineer?
NHTSA has 39 complaints about the electrical system of the 2008 Mercury Mountaineer, 41% of the model year's 96 complaints. The component named most often is ignition (2 mentions).
Is there a recall for 2008 Mercury Mountaineer electrical problems?
No. NHTSA lists no electrical system recall for the 2008 Mercury Mountaineer, though it has 1 recall 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 2008 Mercury Mountaineer electrical problems start?
Half of the complaints with a recorded mileage happened before about 65,000 miles, and 20% before 25,000 miles.
Is it dangerous?
Owners linked 2 crashes, 0 fires and 0 injuries to electrical system problems on this model year. If you notice symptoms, have the car checked before driving further.
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.