How To Disassemble Your AC Condensing Unit To Check The Fan, Fan Motor, And Condensing Coils

Has your central air conditioning started cycling on and off even though you can hear it start up properly? Does the fan in the condensing unit seem to spin slower than normal or make a loud noise while spinning? All of these problems can be signs of problems in the condensing unit – namely in the fan assembly and the closely related condensing coils.   

Checking the fan assembly and coils for problems is a fairly straightforward process with little risk if you turn off the electricity – either at the fuse box or the circuit breaker-- and work carefully. Finding a problem can help you determine the cause of your unit's malfunctions.

Things You Need:

  • Screwdriver
  • Wrench
  • Foaming coil cleanser
  • Stiff brush

Step 1: Check the Fan Assembly

Locate the domed grated covering on top of the condensing unit. Unscrew the fasteners surrounding the dome and put the screws aside somewhere you won't lose them. Lift the grated cover up and the fan assembly attached underneath will come with it.

Note that there are still attached wires so don't jerk the assembly out violently or try to lift it up high. Simply lift up, flip over, and then set the grated-side down on the exterior of the condensing unit. You should now be looking at the fan blades, which are attached to the motor that sits underneath.

Look for dents or breakages in the blades. Small dents can be gently pounded out by hands but breakages and major dents mean you need a new fan.

Use your hand to push the fan around in a few full rotations and make note of how easily it turns.  If the fan turns easily but you've been hearing it slow down while running, you likely have a blown motor that needs replacing. If the fan wobbles when you turn it, check the set screw at the center of the blades to see if it is tightened. Tighten the screw with a wrench, if necessary, and then test the fan again.

Step 2: Check the Coils

You will need to gain access to the interior condensing unit to check the coils. The condensing unit has a cover that comes off via fasteners of some kind, which are usually either screws or latches. Locate the fasteners, remove the fasteners, and then remove the condensing unit cover.

Look inside and you should easily spot the condensing coils attached to an interior wall. Visually inspect the coils for any signs of breakage or denting and, if you spot these problems, immediately call an HVAC tech for a service call. If the coils look undamaged but dirty, you can perform the cleaning yourself.

Purchase a foaming coil cleanser at the hardware store and follow the package directions for application to your coils. The formula is no-rinse so you will need to let the cleaner sit on the coils for a specified period of time and it will then dissolve on its own.

Do the coils still look a bit dirty after the cleaner? You can use a stiff brush but a gentle hand to scrape loose any remaining dirt. 

For any further assistance, contact local professionals, such as those from Ron Hammes Refrigeration.