How to Replace an RV Rooftop Air Conditioner: Dometic Penguin II Install Guide

If your rooftop air conditioner is more than a decade old, struggling to keep up, or rattling like a toolbox on the highway, replacement is usually smarter than repair — and it's a genuinely achievable DIY job. Nearly every RV rooftop AC drops into the same industry-standard 14″ × 14″ roof opening, which means a modern low-profile unit like the Dometic Penguin II 15,000 BTU is a direct swap for most old units.

Here's the full process. Budget a half day, and recruit a second person for the lifting.

Before you start

• Confirm the opening. Measure your existing roof cutout — you're looking for 14″ × 14″. Still unsure whether you need 13,500 or 15,000 BTU? Read our BTU comparison guide.
• Ducted or non-ducted? The Penguin II works both ways. Non-ducted installs need an air distribution box on the ceiling side; ducted rigs reuse the existing ceiling plenum.
• Kill the power. Disconnect shore power and switch off the AC breaker. You'll be working with 120V wiring.
• Check your roof rating. You'll be walking on the roof with a unit that weighs around a hundred pounds — use plywood to spread your weight on thinner roofs.

Step 1: Remove the old unit

1. Inside, remove the ceiling assembly (shroud, filters, and the bolts that clamp the unit to the roof). Photograph the wiring connections before you disconnect anything.
2. On the roof, cut through any old sealant around the base with a putty knife.
3. Lift the old unit off the opening — this is the two-person part — and lower it down carefully.
4. Scrape the old gasket residue off the roof around the opening and clean the mounting surface. A clean, flat seating surface is what keeps water out; don't rush it.

Step 2: Set the new Penguin II

1. The new unit comes with its roof gasket. Set the Penguin II over the opening and align the gasket with the cutout — the aerodynamic housing points forward.
2. From inside, install the mounting bolts through the ceiling frame and tighten them evenly, in a cross pattern, to the torque in the included instructions. This compresses the gasket uniformly. Over-tightening one corner is the #1 cause of both leaks and vibration.

Step 3: Wiring and ceiling assembly

1. Reconnect the 120V supply per the wiring diagram in the manual — it matches what you photographed in almost every replacement scenario.
2. For non-ducted setups, mount the air distribution box; for ducted, connect the divider and duct openings.
3. Install filters and the interior grille.

Step 4: First startup

1. Restore the breaker and shore power.
2. Run the fan first, then cooling. Compressor startup should settle into a smooth hum — the Penguin II's rib-reinforced base pan and low-profile housing make it noticeably quieter on the road and at the campsite than decade-old units.
3. After the first rain (or a hose test), check the ceiling perimeter for any sign of moisture. A properly torqued gasket needs no extra sealant on most installs.

Common mistakes to avoid

• Reusing a crushed gasket from the old unit. Always seat the new one.
• Sealing with self-leveling lap sealant “just in case.” The gasket is the seal; burying the base in sealant makes future service miserable and can trap water.
• Uneven bolt torque — leads to leaks on one side and rattles on the other.
• Ignoring the refrigerant type. The Penguin II runs modern R-410A — a sealed system, nothing to charge or top up on installation.

FAQ

Can one person do this install? The wiring and torque work, yes. The roof lift, no — get help or rent a lift for the unit itself.

Will it work with my existing thermostat? Non-ducted installs use the controls on the air distribution box. Ducted installs vary by rig — check the control kit compatibility in the manual before ordering.

How long does it take? Most first-timers finish in 3–5 hours including cleanup.

Ready to swap? The Dometic Penguin II 15,000 BTU ships free with free 30-day returns — and code RVSAFE10 takes 10% off your order.