Living full-time in an RV changes your math on repairs fast. You start calculating the cost of parts versus the cost of a mobile tech, and you realize that most of these jobs — once you understand the system — are absolutely within reach for someone who’s willing to read a guide, watch a video, and take their time. On the Forest River Impression, the rooftop AC unit is one of those systems you cannot afford to ignore — when it starts humming, struggling to kick on, or the fan stops moving air altogether, the culprit is almost always a failing run capacitor or a worn-out fan motor, and in the middle of summer, that’s not a comfort issue, it’s a livability crisis. The good news is that both repairs involve straightforward components that cost a fraction of a service call, and with the right steps, you can have cold air blowing again the same afternoon. This guide walks you through exactly how to diagnose which part has failed, how to safely replace it, and what to double-check before you button everything back up.
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 Problems & Safety
Start by identifying symptoms like weak cooling, unusual noises, or complete AC failure on your Forest River Impression. Turn off power at the main breaker and disconnect the RV from shore power to ensure your safety before beginning any work.
Step 2: Remove Rooftop AC Shroud Cover
Climb onto your RV roof and locate the mounting bolts securing the outer shroud of your rooftop AC unit. Carefully unbolt and lift away the shroud cover, keeping track of all fasteners and noting the gasket condition for potential replacement.
Step 3: Access Capacitor & Fan Motor
Once the shroud is removed, you’ll see the dual run capacitor mounted on the AC unit frame and the fan motor assembly. Take photos of the wire connections before proceeding to ensure accurate reassembly of your electrical components.
Step 4: Replace Capacitor & Fan Motor
Disconnect the wires from the old capacitor using needle-nose pliers, then unbolt it from its mounting bracket and install the new Dometic/Coleman-Mach capacitor in its place. Remove the fan motor bolts, disconnect its wiring harness, and install the replacement motor, ensuring proper alignment with the blower wheel.
Step 5: Clean Evaporator & Condenser Coils
Apply the AC coil cleaner foam to both the evaporator and condenser coils, allowing it to sit for the recommended time to dissolve debris and mold. Use your fin comb tool to gently straighten any bent fins on the coils to restore proper airflow and cooling efficiency.
Step 6: Reinstall Shroud & Seal Gasket
Position the outer shroud cover back over the AC unit and secure all bolts firmly. Apply self-leveling lap sealant around the gasket perimeter to create a weather-tight seal and prevent roof leaks around your AC unit.
Step 7: Test System Performance Thoroughly
Restore power to your RV and turn on the AC at the thermostat, listening for smooth motor operation and checking for proper cooling. Use the non-contact infrared thermometer to verify that air temperature at the vents drops appropriately within 10-15 minutes of operation.
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 |