Thor Palazzo – AC Capacitor & Fan Motor Service

I’ve got my workbench set up in the shade behind bay two, and sitting on it right now is a Dometic AC shroud I pulled off a Thor Palazzo last week. The owner called me at 2 PM on a Saturday—kids playing in the background, wife asking what was wrong—because the unit had quit mid-afternoon. He told me the same thing I’ve heard a hundred times: it started humming strangely a few weeks back, then got louder, and finally just stopped responding. What kills me is how predictable it is. That drawn-out hum before the compressor kicks in, or the fan straining like it’s fighting invisible resistance—those are exactly the warning signs that show up three, sometimes four weeks before total failure. By the time I roll up, the run capacitor has given up, and it’s usually dragged the fan motor down with it. I’ve learned that this two-part collapse happens together far more often than you’d expect, which is why I’m walking you through the diagnosis, the replacement, and the safety steps I actually use in the field so you can get your cooling back without waiting on a service call to wreck your trip.

Diagnosing the Capacitor Failure on Your Palazzo’s Dometic Rooftop Unit

When your Dometic rooftop AC produces that extended hum for several seconds before the compressor engages—or refuses to start at all—you’re almost certainly staring at a run capacitor that’s reached the end of its service life. Push it further and you risk burning out the fan motor entirely, leaving you with a cooling system that’s completely offline.

Why this replacement works

• Matches Dometic part 3312195.000 exactly—no cross-referencing rabbit holes or hunting through obscure part catalogs.
• The fan motor engages immediately and smoothly once installed; that hesitation and delayed spin-up vanishes the moment power flows through.
• Built to OEM durability specs, which means it won’t follow the pattern of cheaper knockoff units that quit again inside of 18 months.

Where the limits are

• Getting to the capacitor requires opening the AC shroud and carefully disconnecting high-voltage wiring—if 240V connections make you nervous, 20 minutes of technician time is money well spent for peace of mind.
• Stock delays happen, especially with non-Prime inventory on larger retail platforms, which can mean 2–3 days waiting for the part when you’re sitting in a July campground baking in 95-degree heat.

I replaced one of these on a Palazzo that had been running on fumes for two weeks, and I half-expected the motor to be already cooked—but it fired right up and stayed cool the rest of the summer, which told me the owner had caught it just in time. Grab the 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 before that humming becomes silence.

Parts and Tools

• Replacement dual run capacitor matched to the microfarad and voltage rating on the old one (60/5 MFD for Dometic units) — check current price
• Replacement fan motor assembly (Dometic 3312195.000 or equivalent) if the motor has seized or won’t spin freely — check current price
• Needle-nose pliers or small wire strippers for disconnecting spade terminals from the capacitor
• Multimeter set to capacitance mode to verify the old capacitor is actually failed before removal
• Flashlight or headlamp for visibility inside the shroud and around the mounting bracket
• Socket set or wrench to remove the shroud fasteners and any motor mounting bolts
• Electrical tape and a marker for labeling wire connections before disconnection

Step-by-Step Instructions

Step 1: Kill power to the rooftop unit at the breaker

Locate your AC disconnect switch or breaker panel and flip the 120V AC circuit that feeds your rooftop Dometic unit to the off position. Wait 30 seconds to allow any residual charge to bleed from the capacitor. Do not skip this step—capacitors can hold a dangerous charge even after power is cut. If you’re unsure which breaker controls the AC, flip it and have someone inside confirm the unit is dead before you touch anything.

Step 2: Access the shroud and photograph the wire layout

Climb onto the roof safely and locate the AC shroud—it’s the large metal box housing the compressor and fan motor. Remove the fasteners holding the shroud in place (usually four to six bolts or clips). Before disconnecting anything, take clear photos of how the wires attach to the capacitor terminals and motor leads. This photograph is your insurance against reassembling it wrong. Note the color and position of each spade terminal.

Step 3: Test the capacitor with a multimeter

Set your multimeter to capacitance mode. Touch the probes to the capacitor terminals and read the value. A healthy 60/5 MFD capacitor should read close to that specification. If it reads zero, significantly lower, or shows an open circuit, it’s failed. If the reading is within spec but the unit still won’t start, the motor itself may be seized—spin the fan blade by hand to check for resistance or grinding.

Step 4: Disconnect the old capacitor and motor leads

Using needle-nose pliers, carefully pull each spade terminal off the capacitor. Work slowly to avoid bending the terminals. If the motor is being replaced, disconnect its lead wires the same way. Label each wire with electrical tape and your marker before removal so you can’t mix them up during reinstall. Keep the wires organized and visible—don’t let them fall into the shroud where you’ll lose them.

Step 5: Remove the old capacitor and motor if necessary

The capacitor usually clips or bolts to a bracket inside the shroud. Unclip or unbolt it and set it aside. If the motor is being replaced, unbolt it from its mounting bracket—typically two or three bolts. Lift it straight out and set it on your workbench. If you’re only replacing the capacitor, leave the motor in place and skip this step.

Step 6: Install the new capacitor and motor

Position the new capacitor on the same bracket and secure it with the original clip or bolt. If installing a new motor, align it with the mounting holes and torque the bolts snug—don’t over-tighten, as the mounting bracket is aluminum. Double-check that the fan blade spins freely by hand and doesn’t rub the shroud. Verify the motor shaft is fully seated in any coupling or connection point.

Step 7: Reconnect wires and reassemble the shroud

Using your photograph as a guide, reconnect each spade terminal to its original position on the capacitor and motor. Push each terminal firmly until it seats with a click. Reinstall the shroud and tighten all fasteners evenly. Do not over-tighten—you’ll crack the plastic or strip the bolt holes. Ensure no wires are pinched between the shroud and the roof.

Step 8: Restore power and test the unit

Climb down from the roof and flip the AC breaker back on. Set your thermostat to cool and listen for the compressor to engage within 30 seconds. The fan should spin smoothly without humming or grinding. Feel the condenser coil for warm air discharge. If the unit starts normally and cools, you’re done. If it hums again or won’t start, turn it off immediately and recheck your wire connections against your photograph.

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