After sitting idle all winter, your air conditioning unit has probably gotten a bit dusty and dirty. If you simply turn it on come summer, you will end up blowing that dust and dirt into your home. The debris can even cause damage to the fan and motor in some circumstances. You can avoid these issues by setting aside some time to clean out the external unit before the cooling season resumes.
Clean up around the unit
Wind and drifting snow tends to deposit a lot of debris around the exterior housing of the AC unit. Leaves, twigs, and even garbage can collect there too. Rake this debris up and dispose of it so it isn't in your way as you work. This will also prevent additional debris from getting inside the unit. In fact, it's good practice to keep the area around the AC unit clear at all times, regardless of whether it is in use or not.
Shut down the power
You don't want to chance an electrical shock. Cutting off power at the main AC switch or thermostat isn't enough. You also need to turn off the circuit breaker that sends power to the air conditioner. Just make sure to turn it back on afterward.
Remove and clean the housing
The outer housing is typically held on with a few screws, although there are some models that just snap into place. Locate the screws and remove them, if applicable, and then lift the housing or upper panel off the unit. You can set these aside and hose them off with your garden hose to remove any dust or dirt.
Clean out the interior
There may be leaves and other debris inside the unit. You can remove all of this with a shop vacuum. Spray the interior of the unit down with your hose so that water comes out of the sides. This forces any dirt out of the unit entirely, instead of forcing it further into the unit.
Fix the fins
The thin slats, or fins, on the exterior of the unit pull air through the condenser. They can become smashed over time, which inhibits air flow through the AC. You can purchase a tool called a fin comb, which is used to straighten these fins so that the AC works better.
Once the AC unit is clean, you can reassemble it and flip the power back on. Then, all you need to do is change out the filter before you begin using the unit. For more help, contact an AC contractor like Aggressive Mechanical Contractors, Inc. in your area.