Thor Four Winds – AC Capacitor & Fan Motor Service

I’m standing in front of a Thor Four Winds right now with the access panel off the rooftop AC unit, compressor humming like it’s working hard but the fan blades aren’t moving at all. Hand on the housing—it’s hot enough that I’m not leaving my palm there long. This is the moment where most owners start pricing out a full replacement unit and calling their bank, but I’ve seen this exact scenario play out a hundred times, and it almost always comes down to two cheap parts: a failed run capacitor or a motor that’s seized up. Catch it early and you’re out maybe forty bucks in materials. Let it sit and cook the compressor? You’re looking at a four-figure hit. I’ve built a repeatable diagnostic process through countless flips and side-work troubleshoots—what you’re about to read is that actual sequence, field-tested on rigs exactly like yours, not some dealer pamphlet version. Before you start looking at replacement costs for the whole AC unit, walk through this first.

The Run Capacitor That Powers the Dometic Rooftop Fan on Four Winds Models

When your Dometic compressor is running—you can hear it laboring—but the fan motor stays locked and there’s no cold air moving through the ducts, a dead or failing capacitor is almost certainly your culprit. The capacitor is what shifts the electrical phase so the fan motor can turn; without it working, the compressor runs in a bind and slowly cooks itself toward failure.

Why this part works

• Matches the Dometic OEM part number 3312195.000 down to the terminal configuration—no splicing, no adapter hunting, it seats exactly where the old one came out.
• Rated at 60/5 MFD, which is the spec sheet requirement for Four Winds Dometic systems; slip it in, power up the AC, and the fan blade starts spinning instead of sitting dead.
• Built with thicker housing and stronger internals—not a disposable part that fails every season if you’re using your AC hard, it’s made to last if you’re not hammering it 24/7 in 135-degree conditions.

Where it falls short

• Standard shipping is 5–7 business days; if you’re stranded in August heat and need this installed tomorrow, you’re either expediting the cost or sitting tight, and neither option feels good when the temperature inside is climbing.
• Sometimes the capacitor is the messenger, not the disease—if that compressor was already pulling high amps before the cap failed, the motor windings inside may be heat-damaged beyond saving, and swapping the capacitor won’t fix a cooked motor.

I once swapped the capacitor on a Four Winds and the fan still wouldn’t turn, which made me wonder for a solid 20 seconds if I’d grabbed the wrong part—until I realized the motor shaft was seized from months of sitting idle. 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

Parts and Tools

• Replacement run capacitor matched to the microfarad and voltage rating on the old one (Dometic 3312195.000 or equivalent 60/5 MFD) — check current price
• Replacement fan motor assembly (Dometic 3312195.000 or equivalent) if the motor does not spin freely after capacitor replacement — check current price
• Needle-nose pliers or terminal puller for safe disconnection of spade terminals without bending
• Multimeter set to capacitance mode (or ohms mode for quick continuity check)
• Insulated screwdriver set (Phillips and flathead) for access panel and terminal fasteners
• Photograph or phone camera to document terminal positions and wire routing before disconnection
• Work gloves and eye protection for rooftop work and handling aged electrical components

Step-by-Step Instructions

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

Locate your RV’s main electrical panel and flip the breaker labeled for the rooftop AC unit to the OFF position. Wait 30 seconds, then test the AC wall thermostat—it should not respond. This prevents shock or arc when you touch the capacitor terminals. Even with the breaker off, a charged capacitor can deliver a nasty jolt, so treat every terminal as live until you’ve discharged it.

Step 2: Access the rooftop unit and photograph the capacitor setup

Climb safely to the roof using a ladder and secure footing. Remove the access panel covering the Dometic AC unit (usually four to six Phillips screws). Before touching anything, photograph the capacitor terminals and wire routing from multiple angles. Note which wire connects to which terminal—red to common, black to fan, brown to compressor. This photo prevents costly reconnection mistakes.

Step 3: Discharge the capacitor safely

Using an insulated screwdriver, touch the blade across both terminals simultaneously to bleed any residual charge. You may see a small spark—this is normal and means the capacitor held charge. Repeat this step twice more to be certain. Do not skip this; a charged capacitor can cause injury or damage sensitive electronics.

Step 4: Test the capacitor with a multimeter

Set your multimeter to capacitance mode (µF setting). Touch the probes to the capacitor terminals. A healthy 60/5 MFD capacitor should read between 54 and 66 microfarads on the 60 side and 4.5 to 5.5 on the 5 side. If the reading is zero, climbing toward infinity, or wildly off spec, the capacitor is dead. If the reading is in spec, move to motor testing before replacing.

Step 5: Test the fan motor for seizure

Disconnect the fan motor wires from the capacitor terminals using needle-nose pliers (photograph first). Gently try to spin the fan blades by hand—they should rotate freely with minimal resistance. If the blades are locked solid or grinding, the motor is seized and needs replacement. If they spin freely and the capacitor tested bad, the capacitor is your only repair. If both test good, check compressor discharge line temperature and refrigerant charge before concluding the AC is functional.

Step 6: Disconnect and remove the old capacitor

Using needle-nose pliers, carefully pull each spade terminal off the capacitor posts. Do not twist or bend the terminals—pull straight out. If a terminal is corroded or stuck, apply a tiny drop of penetrating oil and wait two minutes. Once all three wires are free, unscrew the capacitor mounting bracket and lift the old unit clear. Set it aside; do not discard it yet in case you need to verify the rating.

Step 7: Install the new capacitor and reconnect terminals

Position the new capacitor in the mounting bracket and secure it with the original screw. Align the three terminals so they face the wire connections. Using your photograph as a guide, reconnect the wires: red to common, black to fan, brown to compressor. Push each terminal on firmly until it seats—you should hear a small click. Tug each wire gently to confirm it will not slip off under vibration.

Step 8: Restore power and verify the fan motor runs

Climb down and return to the electrical panel. Flip the AC breaker back to ON. Set the thermostat to cool and listen for the compressor to start. Within 2–3 seconds, the fan blades should begin spinning smoothly. Feel the air coming from the ceiling vents—it should be noticeably cooler within 5 minutes. If the fan does not spin or the compressor shuts down after 10 seconds, turn off the breaker immediately and recheck your terminal connections against your photograph.