The outside air conditioner unit sits on top of slab to help keep it level. Over time, one side of the slab might sink into the soil deeper than the other side. This usually happens on the side that is closest to the house and the dripping water from the roof when it rains. Leveling an air conditioner that has sunken on one side requires an assistant. Since the slab requires some prying, it might be necessary to have two assistants so two people can lift the slab.
Turn off the circuit breakers to both the indoor and outdoor air conditioning units. This prevents the air conditioner from operating while you are re-leveling the slab and also avoids accidental shocks.
Dig a small trench around the outside circumference of the air conditioner slab with a shovel, opposite the side that is too low. Place the bags of gravel next to the low side of the slab.
Position a 4-inch-by-4-inch block of wood on the ground next to the low side of the platform. Place a level across the top of the air conditioner unit. Insert the end of a crow bar under the low side of the slab and drape the crow bar across the top of the wood block.
Push down on the end of the crow bar to pry the slab up until the air conditioner is level. Depending on the size of the slab and how much it is out of level, it might be necessary to ask one of your helpers to push down on the pry bar with you.
Hold the crow bar and ask your helper to shovel gravel from the bag under the slab. Slowly release the hold on the crow bar and allow the air conditioner pad to settle on the gravel.
Check the levelness of the air conditioner. Pry the slab up and fill with gravel as necessary until the air conditioner is level. Turn the circuit breakers back on once the air conditioner is level.