Take out the fuse.
The engine air filter is in the engine compartment , on the passenger side front corner , inside the plastic housing
You cannot and should not disable the air bag.
The cabin air filter on a Mercury Mountaineer is located on the passenger side of the vehicle. The unit is behind the glove box and can be replaced by removing the glove box.
The passenger air bag is disabled by a weight sensor in the passenger seat. If the weight of the occupant is under a predetermined weight or is unoccupied the passenger air bag is automatically disabled.
If you live in the USA, you have to get a form from the National Highway Traffic Safety Administration and have a doctor fill it out proving medical reasoning for airbag disabling.
In the front of the engine compartment , on the passenger side , inside the engine air filter housing
Is it the fan behind the radiator, or the fan that blows air into the cabin?
I'm not sure why you would want to disable this.. There is an on and off switch in the trunk on the passenger side. In the off position the air compressor will not operate.
Some vehicles have a switch to disable the passenger air-bag. Others have a system that can detect a suitable (transponder equipped) child-seat in the passenger seat, and deactivate the air-bag while the seat is fitted. Unless the vehicle has such a switch, or is equipped with such a system, it is not normally possible to disable the passenger air bag without also disabling all the air bags and seat-belt pre-tensioners. For this reason it is recommended that child seats be fitted in the rear, or that those with medical reasons that make an air bag "undesirable" are seated in the rear.
The rubber valve stems are on the wheels , they allow you to put air in the tires
THE REFRIDGERANT USED IN A 98 MOUNTAINEER IS 134A. THAT INFO IS ON A STICKER UNDER THE HOOD THAT TELLS TYPE AND CHARGING CAPACITY.
Disconnect the negative battery terminal and remove the fuses pertaining to the air-bag(s)