Just as a dirty filter can cripple your air conditioning unit’s ability to cool your home, dirt and debris on the outdoor portion of your A/C unit can do the same. This outdoor unit is called the condenser, and it contains cooling tubes, fins, and a blower fan. Behind the unit, on the exterior wall of your home, you should find a box containing an electrical shutoff.
Before cleaning your condenser unit, you should open up that box and either flip the switch inside to “off,” or pull out the block shutoff. If you can’t figure it out, just go inside and turn off your A/C unit at the breaker box. Either way, you need to shut off power to the unit.
Now, get out your shop vac, put on the soft-bristle brush attachment, and vacuum the outside of the fins to remove any debris. Pull up any weeds or grass growing within two feet of the unit. If you see crushed or bent fins on the outside of the unit, you can gently straighten them with a butter knife, but be careful -- and don’t insert the knife blade more than half an inch into the unit.
Once you’ve finished cleaning the outside of the air conditioning unit, unscrew the top of the unit and gently lift out the fan. Don’t put any strain on the electrical wiring as you do so. Wipe off the interior of the unit with a damp cloth. Finally, use moderate water pressure from a garden hose to spray off the fins from the inside. Replace the fan, screw the top back on, and restore power to the unit.