Tiffin Allegro Bus – AC Capacitor & Fan Motor Service

Skip this repair and your Tiffin Allegro Bus AC won’t just underperform—it’ll trap you in a rig that either won’t cool at all or keeps nuking your breaker every time you fire it up. A weakening capacitor or dragging fan motor is the kind of failure that sneaks up: one week the AC is sluggish on startup, the next week it’s cutting out mid-cycle, and by week three you’re overheating in July with no backup plan and a service bay that’s booked solid. I’ve watched owners ride this out too long, thinking it’ll limp along, only to watch a $60 capacitor neglect turn into a $1,200 compressor replacement. The motor can’t spin up without that capacitor doing its job, and when it struggles, it pulls hard amperage that your breaker can’t handle. This walk-through covers everything I do to spot the problem, swap out the capacitor and fan motor on the Allegro Bus, and get you back to real cooling—with no prior experience required.

Replacing the Capacitor on Your Dometic AC Unit

A failed capacitor on your Tiffin Allegro Bus Dometic rooftop AC doesn’t just rob you of cold air—it forces your motor to draw excessive current on every startup cycle, and that’s when your breaker gets tripped. Fix it before summer heat pins you down with no AC and no power to run anything else on that circuit.

Advantages of the right replacement

• Fan and compressor spin up with the smooth authority they should have—no more stumbling starts or breaker trips when the system cycles on.
• Matches the Dometic 3312195.000 specification exactly; your voltage and microfarad rating are locked in with your existing hardware, no compatibility headaches.
• Installation is a 15-minute job from rooftop to cool air—unclip the old capacitor, disconnect two terminals, secure the new one in the bracket and you’re finished.

Gotchas to know about

• Inventory on marketplace suppliers swings wildly; a Friday order might not show up until the following week, leaving your AC offline longer than you planned.
• Some replacement units ship with the mounting bracket not fully seated in its clamp—test the fit before you pack away your tools and come down from the roof.

I pulled the old capacitor thinking maybe it was just dusty, caught it with a multimeter and saw zero microfarads—I almost wasted a day troubleshooting the motor itself when the capacitor was already dead. 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 dual run capacitor matched to the microfarad and voltage rating on the old one (60/5 MFD for Dometic 3312195.000) — check current price
• Replacement AC fan motor assembly for Dometic 3312195.000 rooftop unit — check current price
• Needle-nose pliers or terminal puller for safe capacitor wire removal
• Insulated screwdriver set (Phillips and flathead) for access panel and terminal fasteners
• Multimeter with capacitance setting to test the old capacitor before removal
• Electrical tape and wire labels or masking tape to mark wire positions before disconnection

Step-by-Step Instructions

Step 1: Kill power to the AC circuit at the breaker panel

Locate your main breaker panel inside the Allegro Bus and flip the 120V AC breaker serving the rooftop unit to OFF. Wait 60 seconds to allow any residual charge to bleed from the capacitor. Do not skip this step—capacitors hold voltage even when power is cut, and a shock from a live capacitor can cause serious injury. Verify the breaker is fully in the OFF position before proceeding.

Step 2: Access the AC unit and photograph the wire configuration

Climb onto the roof using a stable ladder and secure footing. Locate the Dometic rooftop AC unit—it’s the large box mounted above the main living area. Remove the access panel or shroud covering the motor and capacitor assembly (usually four to six Phillips screws). Before touching any wires, take a clear photo of the capacitor terminals and all wire connections. This photo is your map for reassembly and prevents reversed polarity or crossed wires.

Step 3: Test the capacitor with a multimeter to confirm failure

Set your multimeter to the capacitance (µF) setting. Touch the probes to the capacitor terminals. A healthy 60/5 MFD capacitor should read close to 60 microfarads on the run side. If it reads significantly lower (below 50 µF), reads zero, or the meter shows an open circuit, the capacitor is dead. This test confirms the problem before you disconnect anything and rules out a motor-only failure.

Step 4: Discharge the capacitor safely and remove wire terminals

Use an insulated screwdriver to short the capacitor terminals together for 3 seconds to fully discharge any remaining voltage. Label each wire terminal with masking tape (mark them C, R, S for common, run, and start, or use numbers 1, 2, 3). Using needle-nose pliers, gently pull each spade terminal straight off the capacitor posts. Do not twist or yank—spade terminals bend easily and won’t seat properly on the new capacitor.

Step 5: Remove the old capacitor and install the replacement

Unscrew or unclip the mounting bracket holding the capacitor in place. Lift the old capacitor out and set it aside. Position the new 60/5 MFD capacitor in the same bracket and secure it with the original fastener. Verify the capacitor sits flat and does not touch any metal surfaces or wiring. Reconnect the three spade terminals to the new capacitor posts in the exact order shown in your photo—common, run, and start. Push each terminal firmly until it clicks or seats fully.

Step 6: Inspect and test the fan motor for mechanical drag

Spin the fan motor shaft by hand (with power still OFF). It should rotate freely with minimal resistance. If it feels stiff, grinds, or won’t turn, the motor bearings are worn and the motor must be replaced. If the motor spins freely, reconnect power at the breaker and run the AC on low for 30 seconds. Listen for smooth startup and normal fan noise. If the motor hums but doesn’t spin, or if the breaker trips immediately, the motor is seized and requires replacement.

Step 7: Verify cooling performance and monitor for breaker trips

Set the thermostat to cool mode and run the AC for 10 minutes. Feel the air coming from the vents—it should be noticeably cold within 2 to 3 minutes. Check that the compressor cycles normally without stuttering or clicking on and off. Monitor the breaker panel for any trips over the next 24 hours of operation. If cooling is restored, startup is smooth, and the breaker holds steady, the repair is complete. If the breaker trips again or cooling is weak, the motor is likely the culprit and must be swapped.