Tiffin Open Road Allegro – AC Capacitor & Fan Motor Service

Tiffin’s Allegro coaches are solid builds, but there’s something the factory service bulletins and owner’s manuals gloss over: the Dometic rooftop AC units on these rigs have a lifespan that’s almost entirely dictated by one small, cheap component that nobody thinks about until it’s already gone bad. The run capacitor degrades quietly through heat cycles, the fan motor starts working twice as hard to compensate, and somewhere between year three and year five you’re either looking at a complete condenser motor replacement or a fried control board. The trap is timing — catch the capacitor failing while it’s still just a capacitor and you’ve spent $60 and a Saturday morning on the roof. Ignore the early warning signs and you’re into a $400+ repair that might leave you without air conditioning in the middle of summer. I’ve pulled apart enough Allegros to recognize the pattern cold, and this walkthrough shows you exactly what to look for and how to handle the fix before it cascades into something worse.

The Allegro’s Dometic AC: Why the Capacitor Fails First

The sequence is always the same on these units: the run capacitor loses its charge capacity from thermal stress, so the fan motor has to draw harder to maintain airflow, and that extra current load eventually burns out windings or trips the circuit before the motor seizes entirely. Swap the capacitor while it’s still functional and you’re looking at an $80 parts-and-labor job; wait until the motor starts failing and you’re replacing both components at $400-plus, with the added risk of collateral damage to the control board.

Parts and Tools

• Replacement run capacitor rated 60/5 MFD at 370V AC, matched to Dometic 3312195.000 specifications — check current price
• Needle-nose pliers or small adjustable wrench for terminal fasteners
• Multimeter with capacitance setting (or dedicated capacitor tester)
• Insulated screwdriver set for control panel access
• Electrical tape and wire markers for labeling connections
• Replacement fan motor assembly (Dometic 3312195.000) if capacitor test confirms motor damage — check current price

Step-by-Step Instructions

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

Locate your main 120V AC breaker panel inside the Allegro and switch off the circuit dedicated to the rooftop air conditioner. Wait 30 seconds, then use a multimeter set to AC voltage to confirm zero voltage at the AC unit’s power terminals on the roof. This prevents shock and protects the control board during diagnosis. Do not skip this step—capacitors can hold residual charge even after power is cut.

Step 2: Access the AC shroud and photograph the capacitor terminals

Climb onto the roof using a ladder and secure footing. Locate the Dometic unit’s access panel on top of the shroud (usually held by four Phillips screws). Remove the panel and take a clear photo of the capacitor terminals and wire connections before touching anything. Note which wire connects to which terminal—the capacitor has two terminals and the wires are often color-coded but faded. This photo prevents reconnection errors.

Step 3: Test the capacitor with a multimeter or capacitor tester

Set your multimeter to capacitance mode (or use a dedicated capacitor tester). Discharge the capacitor fully by touching an insulated screwdriver across both terminals. Then probe each terminal with the meter leads. A healthy 60/5 MFD capacitor should read between 54–66 MFD on the 60 side and 4.5–5.5 MFD on the 5 side. If readings are significantly lower or the meter shows zero, the capacitor has failed and must be replaced. If readings are normal but the fan still won’t run, the motor itself is likely damaged.

Step 4: Disconnect the old capacitor and remove it

Using needle-nose pliers or a small wrench, loosen the terminal nuts on both capacitor leads. Slide the wire terminals off the capacitor posts. If the capacitor is mounted in a bracket, unbolt or unclip it from the frame. Inspect the mounting area for corrosion or heat damage. If the bracket or surrounding components show burn marks or melting, the motor has likely overheated and will need replacement alongside the capacitor.

Step 5: Install the new capacitor and reconnect terminals

Position the new 60/5 MFD capacitor in the same orientation and mounting location as the original. Slide the wire terminals onto the new capacitor’s posts, matching the wire colors or positions from your photo. Tighten the terminal nuts firmly but do not over-torque—hand-tight plus a quarter turn is sufficient. Ensure no wires are pinched or touching the shroud. Double-check that all connections are secure before proceeding.

Step 6: Restore power and test the fan motor

Climb down from the roof and return to the breaker panel. Switch the AC circuit breaker back on. Return to the roof and listen for the fan motor to start within 10 seconds. The fan should spin smoothly and quietly. If the fan does not start, immediately kill the breaker again and check your terminal connections. If connections are correct but the motor still won’t run, the motor windings are burned out and the motor assembly must be replaced.

Step 7: Run the AC system for 15 minutes and verify cooling

Set the thermostat to cooling mode and allow the unit to run for at least 15 minutes. Check that cold air is flowing from the interior vents and that the compressor is cycling normally (brief on-off cycles, not continuous running). Feel the condenser fins on the roof unit—they should be warm, not hot. If the unit runs smoothly and cooling is restored, the repair is complete. If the fan cycles on and off erratically or the unit shuts down after a few minutes, a secondary fault may exist and further diagnosis is needed.

What works

• Exact match to the Dometic 3312195.000 specification — no improvisation on microfarad ratings or voltage tolerance. The fan spins up cleanly after replacement and draws normal amperage instead of that labored, overheating spin.
• Built with the kind of durability that means you’re not replacing it again in three years on the same rig. Right after installation you’ll notice the AC cycles without hesitation or that grinding startup sound.
• Stopping the failure at this stage lets you do a $60 swap, not a full motor disassembly or a mobile technician service call that costs three times as much just for the diagnosis.

What doesn’t

• You’ll need to power down the AC completely, safely discharge the residual voltage stored in the old capacitor (they hold a charge even when unplugged), and access the unit from the roof — that’s not a quick job if you haven’t worked on AC shrouds before.
• If the motor is already pulling fault current when you attempt this repair, a new capacitor by itself won’t rehabilitate damaged motor windings. At that point you’re committed to full motor replacement and this becomes an incomplete fix.

I second-guessed myself on one unit where the fan wouldn’t spin for the first 30 seconds after power-up — turned out the old cap was already partially shorted and this replacement brought the unit back to normal cold-start behavior. Order 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 while the system is still cycling, not after it goes silent.