Complete repair guide for the Keystone Montana – AC Capacitor & Fan Motor Service. Follow these steps to diagnose and fix the issue yourself.
Parts & Tools You’ll Need
- RV AC dual run capacitor (Dometic/Coleman-Mach)
- Rooftop AC fan motor
- RV AC thermostat / control board
- AC evaporator/condenser coil cleaner foam
- Rooftop AC shroud / outer cover
- AC roof gasket & self-leveling lap sealant
- Fin comb / coil straightener tool
- Non-contact infrared thermometer
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Step-by-Step Repair Guide
Step 1: Diagnose AC Issues and Ensure Safety
Begin by turning off your RV’s main electrical breaker and the AC unit to prevent electrical shock during diagnosis. Use your non-contact infrared thermometer to check if the AC is producing cold air, and listen for unusual fan noises or motor grinding that indicate capacitor or fan motor failure.
Step 2: Remove Rooftop AC Shroud Cover
Climb onto your Keystone Montana’s roof and locate the bolts securing the AC shroud to the rooftop unit. Carefully remove all fasteners and lift off the outer cover, setting it aside on a clean surface to avoid damage to the gasket.
Step 3: Replace Dual Run Capacitor Assembly
Locate the cylindrical capacitor inside the AC unit and take a photo of the wire connections before disconnecting them for reference. Remove the mounting bracket bolts, install the new Dometic/Coleman-Mach capacitor in the same orientation, and reconnect the wires according to your reference photo.
Step 4: Service Fan Motor and Coils
Inspect the fan motor for debris, corrosion, or bearing wear, and spray it lightly with appropriate electrical contact cleaner if needed. Apply the evaporator/condenser coil cleaner foam to both coils, allow it to sit for the recommended time, then rinse thoroughly with distilled water and a soft brush.
Step 5: Straighten AC Fin Damage Carefully
Use your fin comb tool to gently straighten any bent aluminum fins on the condenser coil, working in the direction of the fin rows. Work slowly and carefully to avoid puncturing the thin fins, as this improves airflow and cooling efficiency significantly.
Step 6: Reinstall Shroud with New Gasket
Apply a fresh AC roof gasket around the shroud perimeter and position the cover back onto your RV’s air conditioning unit. Reinstall all bolts in a crisscross pattern to ensure even pressure, then apply self-leveling lap sealant around the gasket edges to prevent future roof leaks.
Step 7: Test AC Performance and Monitor Temperature
Restore power to your RV and run the AC system for 15-20 minutes while monitoring the outlet temperature with your infrared thermometer. You should see the discharge air temperature drop to 55-60°F within a few minutes; if temperatures remain above 65°F, shut down and review your capacitor and motor connections.
Recommended Parts
| Part | Link |
|---|---|
| RV AC dual run capacitor (Dometic/Coleman-Mach) | View on Amazon |
| Rooftop AC fan motor | View on Amazon |
| RV AC thermostat / control board | View on Amazon |
| AC evaporator/condenser coil cleaner foam | View on Amazon |
| Rooftop AC shroud / outer cover | View on Amazon |
| AC roof gasket & self-leveling lap sealant | View on Amazon |
| Fin comb / coil straightener tool | View on Amazon |
| Non-contact infrared thermometer | View on Amazon |