After buying, repairing, and reselling more than thirty rigs, I’ve crawled into every corner of every coach body style you can name. I know exactly which systems manufacturers cut corners on, which repairs look scary but are actually straightforward, and which ones will drain your wallet if you wait too long. The rooftop AC on a Keystone Cougar is one I’ve seen fail the same way, over and over — a weak or blown run capacitor kills the compressor’s ability to start, and a failing fan motor usually isn’t far behind, especially on units that’ve spent summers baking on a blacktop lot. Most people hear “capacitor” and immediately picture an expensive service call, but this is genuinely one of the most doable DIY repairs on any RV, and catching it early is the difference between a forty-dollar fix and replacing the entire AC unit. This guide walks you through exactly what I do when I flip a Cougar with a struggling rooftop unit — no fluff, just the process that actually works.
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 Safety Prep
Turn off your RV’s main electrical breaker and locate your rooftop AC unit to identify whether you’re experiencing cooling loss, fan motor noise, or complete system failure. Use your non-contact infrared thermometer to measure the air temperature difference between the return and supply vents, which helps confirm capacitor or motor dysfunction before proceeding with removal.
Step 2: Remove Rooftop AC Shroud Cover
Climb onto your Cougar’s roof and locate the bolts securing the outer AC shroud, then carefully unbolt and lift away the cover to expose the internal components. Take photos of the current wiring configuration before disconnecting any components, as this will serve as your reference guide during reassembly.
Step 3: Replace Dual Run Capacitor Unit
Disconnect the wire terminals from your old capacitor by gently pulling on the connectors, then unbolt and remove it from its mounting bracket. Install your new Dometic or Coleman-Mach dual run capacitor by reversing the process, ensuring all wire terminals are firmly seated and the unit is securely bolted to prevent vibration damage.
Step 4: Service Fan Motor and Connections
Unplug the fan motor wiring harness and remove the mounting bolts holding the motor assembly in place, then carefully lift it out of the AC housing. Inspect the motor shaft for rust or debris, clean the bearing surfaces with a dry cloth, and install your replacement motor by securing it firmly with all mounting bolts torqued evenly.
Step 5: Clean Evaporator and Condenser Coils
Spray your AC coil cleaner foam evenly across both the evaporator coils (located inside the housing) and condenser coils (on the exterior), allowing the solution to penetrate for the manufacturer’s recommended time. Use your fin comb tool to gently straighten any bent fins and improve airflow, then rinse the coils thoroughly with clean water to remove all foam residue.
Step 6: Reseal and Reassemble AC Unit
Apply your self-leveling lap sealant around the edges of the new AC roof gasket, then carefully lower the shroud cover back into position and align all bolt holes. Torque the shroud bolts evenly in a cross-pattern to ensure proper gasket compression and prevent future roof leaks around your AC penetration.
Step 7: Test System Performance and Temperature
Restore power to your RV’s AC system and run it on the highest cool setting for 15 minutes while monitoring the thermostat/control board for proper operation. Use your infrared thermometer to verify that the air temperature difference between return and supply vents is at least 15-20 degrees Fahrenheit, confirming that your capacitor and motor replacement has restored full cooling capacity.
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 |