Thor Palazzo – AC Capacitor & Fan Motor Service

Thor Palazzo – AC Capacitor & Fan Motor Service

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

Parts & Tools You’ll Need

Step 1: Diagnose AC Issues and Prepare Workspace

Begin by running your Thor Palazzo’s air conditioner and listening for unusual humming, buzzing, or clicking sounds that indicate capacitor failure—these typically occur when the fan motor won’t start despite power reaching the unit. Turn off the AC at the thermostat and the main 120V breaker, then wait 5 minutes for residual charge to dissipate before proceeding. Gather your tools on the roof, lay out a drop cloth to protect the RV finish, and take photos of the current wiring configuration for reference during reassembly.

Step 2: Remove Rooftop AC Shroud and Access Components

Unbolt the RV rooftop AC shroud/outer cover using a socket wrench—typically four to six 1/4-inch bolts around the perimeter—and carefully lift it away to expose the internal capacitor and fan motor assembly. Set the shroud aside on a padded surface to prevent damage, and inspect the AC roof gasket for cracks, compression damage, or separation from the rubber seal. Photograph the current component layout, including wire terminals and color-coding, before disconnecting anything.

Step 3: Discharge and Test the RV AC Dual Run Capacitor

Locate the RV AC dual run capacitor (typically a cylindrical component rated 35+5 microfarads at 370V for Dometic or Coleman-Mach units) and use an insulated screwdriver to discharge it by shorting the terminals together—do this twice to ensure complete discharge. With your multimeter set to the 250V capacitance setting, measure the capacitor’s microfarad rating; readings below 90% of the marked specification indicate failure and replacement is necessary. Document the exact microfarad and voltage ratings printed on the capacitor casing before removal.

Step 4: Disconnect and Remove Failed Capacitor Assembly

Take detailed photos of the capacitor’s terminal connections (noting which wires connect to common, run, and herm terminals), then carefully disconnect the spade terminals using needle-nose pliers. Unbolt the capacitor mounting bracket—usually a single 1/4-inch bolt—and slide the capacitor out of its position, being mindful of any remaining residual charge. Inspect the mounting area for corrosion, dust accumulation, or burnt insulation, and clean the bracket with a dry cloth before installing the replacement RV AC dual run capacitor.

Step 5: Install New Capacitor and Verify Fan Motor Continuity

Slide the new RV AC dual run capacitor into the mounting bracket, ensuring it seats fully and securely, then reconnect the spade terminals to their original positions—common to common, run to run, and herm to herm. Before powering up, test the fan motor for continuity using your multimeter’s ohms setting on the motor terminals; you should read 10-30 ohms of resistance indicating a healthy motor winding. If the motor shows open circuit (infinite resistance) or near-zero resistance, the motor requires replacement.

Step 6: Clean Coils and Replace AC Roof Gasket Seal

While the shroud is removed, apply AC evaporator/condenser coil cleaner foam to the aluminum fins in a sweeping motion, allow it to sit for 3-5 minutes, then rinse thoroughly with low-pressure water from a garden hose—this restores cooling efficiency by up to 15%. Use a fin comb/coil straightener tool to gently straighten any bent fins, working in one direction only to avoid damaging the delicate aluminum. Remove the old AC roof gasket by peeling it away carefully, then clean the mounting surface with mineral spirits and allow 10 minutes drying time before applying a new gasket with self-leveling sealant according to manufacturer specifications.

Step 7: Reinstall Shroud and Conduct System Performance Testing

Reposition the rooftop AC shroud/outer cover and reinstall the bolts in a cross pattern (alternating sides) while tightening to 40-50 inch-pounds to ensure even sealing without over-torque. Restore power at the breaker, set your thermostat to cooling mode at 72°F, and verify that the fan motor starts smoothly within 3-5 seconds without humming or chattering sounds. Using a non-contact infrared thermometer, measure the air discharge temperature at the outlet (should read 15-20°F cooler than the return air) and confirm the unit cycles normally over a 15-minute operating period before considering the job complete.