Thor Four Winds – AC Capacitor & Fan Motor Service

Thor Four Winds – AC Capacitor & Fan Motor Service

by

Complete repair guide for the Thor Four Winds – AC Capacitor & Fan Motor Service. Follow these steps to diagnose and fix the issue yourself.

Parts & Tools You’ll Need

Step 1: Diagnose AC Failure and Disconnect Power

Start by turning off your RV’s main electrical disconnect switch and breaker for the air conditioning unit to ensure safety before any work begins. Use a non-contact infrared thermometer to measure the temperature differential between the AC intake and output vents—a difference of less than 12°F typically indicates either capacitor failure (preventing the fan motor from running) or a failing motor itself. Listen for humming sounds without fan rotation, which signals a bad capacitor, versus complete silence, which suggests motor failure.

Step 2: Remove Rooftop AC Shroud and Assess Components

Climb onto your Thor Four Winds roof and locate the four corner bolts securing the rooftop AC shroud/outer cover. Using a 3/8-inch socket wrench, remove these fasteners and carefully lift the shroud away from the AC unit, exposing the capacitor and fan motor assembly. Document the exact wire connections with photos or a diagram before disconnecting anything, as the dual run capacitor typically has three terminals (common, fan, and compressor) that must be reconnected correctly.

Step 3: Test and Replace the Dual Run Capacitor

Using a multimeter set to capacitance mode, test the existing RV AC dual run capacitor against its rated specifications (commonly 45+5 microfarads for the fan and 15+5 microfarads for the compressor on Dometic or Coleman-Mach units). If readings fall below these ranges or show zero continuity, the capacitor has failed and must be replaced. Discharge any residual voltage from the old capacitor by using an insulated screwdriver to short the terminals together before removal, then install the new capacitor by matching the wire terminals to your documented photo references.

Step 4: Inspect and Clean or Replace Fan Motor

With the shroud removed, visually inspect the RV rooftop AC fan motor for visible damage, corrosion, or bearing play by gently rotating the fan blade by hand (with power disconnected). If the motor rotates freely and smoothly, the issue was likely just the capacitor; however, if rotation is stiff or the motor shows rust or burnt insulation, you’ll need to replace it. Unbolt the motor from its mounting bracket using a 1/2-inch socket and disconnect the power wires, then install the new fan motor in reverse order, ensuring the mounting bolts are torqued to 15 foot-pounds.

Step 5: Clean Evaporator and Condenser Coils Thoroughly

With the motor and capacitor exposed, spray the AC evaporator/condenser coil cleaner foam across the entire coil surface, working from top to bottom to allow gravity to carry debris downward through the fins. Let the foam sit for 10-15 minutes, then rinse thoroughly with a soft stream of water from a garden hose, being careful not to bend the delicate aluminum fins. Use your fin comb/coil straightener tool to carefully straighten any bent fins, which restrict airflow and reduce cooling efficiency by up to 15%.

Step 6: Reinstall Shroud with New Gasket and Sealant

Before replacing the rooftop AC shroud, remove the old AC roof gasket completely and clean the mounting surface with a dry cloth to remove debris and old sealant residue. Apply a 1/4-inch bead of RV AC self-leveling sealant around the entire perimeter of the shroud base, then position the new gasket on top and lower the shroud into place. Reinstall all four corner bolts and torque them in an X-pattern (diagonal) to 18-20 foot-pounds to ensure even pressure and prevent leaks.

Step 7: Power On and Verify Complete System Operation

Turn the main electrical disconnect and AC breaker back on, then set your RV AC thermostat/control board to cooling mode at 65°F and listen for the compressor to engage within 30 seconds. Verify that the fan motor runs smoothly and continuously, then measure the output temperature using your non-contact infrared thermometer—you should see at least a 12-15°F temperature drop across the unit within 5 minutes. Allow the system to run for 15 minutes while monitoring for any unusual noises, vibrations, or electrical odors, and confirm that your living space reaches your target temperature.