When you boondock regularly — no hookups, no campground services, no one nearby to help — you develop a different relationship with your rig’s systems than a weekend camper does. Everything has to work. You learn the failure modes, the warning signs, and the repairs before you need them, not during. On a Newmar Bay Star, the rooftop AC unit is one of the first things that will humble you mid-summer — a failing run capacitor or a seized fan motor can turn a functional system into a box of hot air within a single afternoon, and in triple-digit heat, that’s not a comfort issue, it’s a safety issue. I’ve been through this repair firsthand, so what follows isn’t pulled from a service manual — it’s the actual process, with the real parts numbers, the small things that go wrong, and the details that make the difference between a fix that holds and one that fails again in two weeks.
Parts & Tools You’ll Need
- Fits for Dometic 3312195.000 Air Conditioner RV AC Motor Capacitor 60/5 MFD, Heavy Duty Air Conditioner Capacitor Replacement, Compatible with Dometic 3312195000 RV Air Conditioner Models — RV AC dual run capacitor (for Dometic or Coleman-Mach)
- HHQ RV Air Conditioner Motor with Capacitor, Direct Replacement for Coleman Mach RV AC Fan Motor, Replaces Fasco D1092, 1/3 HP, 115 Volts, 1675 RPM, 5-Year Warranty — RV rooftop AC fan motor
- 3106996022 3106996.022 Heat & Cool Thermostat Relay Analog Control Circuit Board Kit for Dometic RV Air Conditioner (White) — RV AC thermostat / control board
- CRC (05084-12PK) Brakleen Non-Chlorinated Brake Parts Cleaner – 14 oz., (Pack of 12) — AC evaporator/condenser coil cleaner foam
- LEDBarz RV Air Conditioner Shroud Cover Screws (10 Pack) for Dometic RV Brisk II and Penguin II Roof Top Air Conditioner, Replacement Parts for Dometic 3310724.0040000002 — Rooftop AC shroud / outer cover
- Dongxw Self Leveling RV Roof Sealant White, 4 Pack Camper Roof Sealant, Lap Sealants for RVs Roofs, Waterproof Flexible RVs Sealants and Caulk for Trailer, Maintenance, Repair — AC roof gasket & self-leveling sealant
- AMI PARTS FCR6 Fin Comb Set for Air Conditioner FCR6 Coil Fin Comb Ring Straighten Evaporator Condensor — Fin comb / coil straightener tool
- FKM Infrared Thermometer Gun Non-Contact Laser Temperature Gun,-58°F~986°F(-50°C~530°C) AdjustableEmissivity,Digital Thermometer Gun for Industrial,Kitchen Cooking,Oven,Automotive,HVAC,Not for Human — Non-contact infrared thermometer
Step 1: Diagnose AC Performance & Safety Check
Start by running your Bay Star’s AC system for 10-15 minutes and note any symptoms: weak cooling, unusual grinding noises, or the compressor cycling on and off rapidly. Use your non-contact infrared thermometer to measure the temperature at the AC outlet—it should read between 50-60°F when the thermostat is set to maximum cooling. Before proceeding, turn off power at your RV’s main breaker and verify the system is de-energized using a multimeter set to AC voltage mode on the capacitor terminals.
Step 2: Access Rooftop AC Unit & Remove Shroud
Climb onto your RV’s roof and locate the Newmar Bay Star’s AC unit, which is typically mounted toward the front section. Unbolt the rooftop AC shroud using a Phillips or flathead screwdriver (usually 6-8 bolts around the perimeter), then carefully lift it straight up to expose the internal components. Inspect and photograph the internal layout to aid reassembly, noting the wire routing and bolt positions.
Step 3: Discharge Capacitor & Disconnect Power
Even with the breaker off, discharge the RV AC dual run capacitor by using an insulated screwdriver to create a short circuit between each terminal pair for 3-5 seconds—you may hear a small pop or see a spark, which is normal. Once discharged, use a multimeter to confirm 0V across the capacitor terminals. Disconnect the two or three wire connectors from the old capacitor (noting their positions) and unscrew the mounting bracket bolt.
Step 4: Install New Dual Run Capacitor
Position your new RV AC dual run capacitor (typically rated 45+5 microfarads at 370V for Dometic or Coleman-Mach units) in the same mounting location and secure it with the bracket bolt—ensure it’s snug but not over-tightened. Reconnect the wire terminals in the exact same configuration as the original, double-checking that each connector is fully seated and secure. Verify the capacitor’s microfarad and voltage ratings match your AC unit’s specifications, which are usually printed on the compressor housing.
Step 5: Replace Fan Motor & Check Bearings
Locate the rooftop AC fan motor (usually a 1/4 to 1/3 HP unit) and disconnect its power harness by gently pulling the connector straight out. Remove the mounting bolts (typically 3-4 bolts) and lift the old motor away, noting its orientation. Install your new RV rooftop AC fan motor in the reverse sequence, ensuring the motor shaft spins freely by hand before reconnecting the harness—it should rotate with minimal resistance and no grinding sounds.
Step 6: Clean Coils & Reseal Unit Housing
Spray your AC evaporator/condenser coil cleaner foam across the aluminum fins and allow it to sit for 5-10 minutes, then rinse thoroughly with a low-pressure water source or compressed air—avoid high-pressure spray that may bend the fins. Use your fin comb tool to straighten any bent fins, working gently from the base outward at a 45-degree angle. Apply a bead of AC roof gasket sealant and self-leveling sealant around the shroud mounting surface before reinstalling, then bolt the rooftop AC shroud down securely.
Step 7: Test System & Verify Cooling Performance
Restore power at your RV’s main breaker and set the thermostat to cool mode at maximum setting, allowing the system to run for 15-20 minutes. Check the AC outlet temperature again with your non-contact infrared thermometer—you should see 50-60°F airflow and hear the fan motor running smoothly without vibration or noise. Verify that the compressor engages within 2-3 minutes and that the interior temperature drops noticeably; if cooling is weak or the motor doesn’t engage, recheck all wire connections and capacitor terminals for loose contacts.