2009 Mercury Mariner Problems

RepairPal has identified the most common problems with the 2009 Mercury Mariner as reported by actual vehicle owners. We'll tell you what the problem is and what it'll take to fix it.

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7
Known Problems

The Mercury Mariner equipped with automatic temperature control may have a problem with frequent fan speed changes when using the heater or air conditioner. Normally, the fan speed changes only to maintain a selected temperature, but when the fan speed changes frequently and needlessly, there is an issue with the fan speed control unit. 

The fan speed control unit, sometimes erroneously called the blower motor resister, regulates the speed for the blower motor in order to maintain the temperature set by the driver. When it fails, the fan will run at random settings, and the climate control will be inaccurate.

Note: this does not affect the temperature of the air that comes from the vents, it affects the amount of air that comes from the vents. 

The repair is simple, and quick. The control unit is located behind the glove box in most models, and removal and installation takes only minutes.

Also note: this only applies to vehicles with single or dual automatic climate control.

The 2008-2011 Mercury Mariner with manual temperature and fan controls may have problems with the the blower motor only blowing air on certain settings. Most commonly the fan will only run on the highest setting. This is a well documented problem, and is caused by a failing blower motor resistor.

Correcting the problem is straight forward, and requires replacement of the small resistor. The resistor is normally found behind the glove box, next to the blower motor.

The check engine light may come on due to failure of the Variable Camshaft Timing (VCT) solenoids. The VCT solenoids will need to be replaced if they are the reason the check engine light came on.

Looseness in the steering shaft and steering shaft coupling U-joint can cause a knocking / popping noise from the steering column when turning. The steering shaft and coupling U-joint will need to be replaced.

If the transmission oil leaks out of left side half shaft area, it may be from a worn axle shaft seal. The seal can be damaged by a poor surface finish on the axle shaft. The axle shaft and seal should be replaced to correct the problem.

Shock bushing failure in the rear can allow the shock absorber to contact the body and cause a squeaking noise over bumps in the rear. The faulty rear shock absorber bushings should be replaced.

The transmission oil cooler may develop a leak, which will require replacement to repair.