There will be two ports with caps on the lines running from the a/c cmpressor. The smaller one is the low side.
On a 2004 Mercury Mountaineer : The ELECTRIC fuel pump is INSIDE the gas tank
The electric fuel pump is inside the fuel tank
In the right front passenger footwell , by the kick panel
According to the 2004 Mercury Mountaineer Owner Guide : ( 22.5 U.S. gallons )
The 2004 Mercury Mountaineer does not have an automatic transmission fluid dipstick . I know that the 2002 and newer Ford Explorer four door versions do not have a dipstick for the automatic transmission fluid level .
fuel gauge not working and power windows and radio.2004 mercury mountaineer.
wheel bearings mountaineer 2004
A door panel on a 2004 Mercury Mountaineer is held on by several screws. Once all the screws are removed the panel can easily come off.
# 24 is a 15 amp fuse for the cigarette lighter , OBD II , in the passenger compartment fuse panel of a 2004 Mercury Mountaineer
Starting with the 2002 model , there is no automatic transmission fluid dipstick on the Mercury Mountaineer ( and the Ford Explorer , 4 door )
To reset the tire pressure sensor on a 2004 Mercury Mountaineer, start by checking and adjusting the tire pressures to the recommended levels. Next, turn the ignition to the "ON" position without starting the engine. Press the reset button, usually located under the steering wheel or in the glove compartment, until the tire pressure light blinks three times. Finally, turn the ignition off and then back on to complete the reset.
Disconnect the negative side of the battery