Can I keep my factory rear AC and add house AC

The short answer and what it really means

Yes, in most modern vans you can keep the factory rear AC and add a house AC. The two systems are separate by design. The factory rear unit uses an engine driven compressor, factory refrigerant lines, an evaporator and ducts in the rear cabin. A house AC is typically an electric system powered by shore power or your battery bank through an inverter, or it can be a high efficiency direct current compressor unit. Because they operate on different energy sources and different plumbing, they can coexist without sharing parts or controls.

Keeping both brings clear benefits. The factory rear AC can pre cool the cabin while driving, move a lot of air to the third row area, and use the engine as the powerplant for cooling during travel. The house AC takes over once parked, giving steady cabin temps without idling. Together they create redundancy for hot climates and give you options whether you are moving or off grid.

Key considerations before adding a house AC

• Electrical capacity: A typical rooftop unit falls around 1200 to 1800 watts while running, with short spikes on startup. Direct current compressor systems vary widely but can pull sustained high amperage from the battery bank. Sizing the battery, inverter, and charging sources is the first gate. Think in energy per hour, not just peak draw. If your goal is to sleep through a summer night, model duty cycle and ambient temps, not just nameplate numbers.

• Charging while driving: Pairing the house AC with a strong alternator to battery charging pathway helps replenish energy used during drive days. A properly set up high output DC to DC charge stage can restore a meaningful portion of the energy consumed by the house AC without stressing the vehicle electrical system.

• Roof structure and placement: Roof AC units require a cutout and proper sealing. Placement affects center of gravity, roof load limits, and shadowing over solar panels. Distance from the sleeping area changes noise perception and airflow feel. Some owners prefer a forward mount to keep cool air drifting rearward at night.

• Condensation management: House AC units produce condensate that must be routed away from the cabin and from sensitive electronics. Well planned drain routing with positive slope and secure exits prevents drips, odors, and corrosion. The factory rear system handles its own condensate separately, so the two do not share drain paths.

• Noise and comfort: Large roof units may have a noticeable hum. Newer variable speed compressors and soft start electronics reduce startup noise and smooth the cycling. Insulation and vibration isolation at the mounting points make a big difference inside the cabin.

• Weight and headroom: The factory rear AC often occupies ceiling space for ducting and bulkheads. If you keep it, plan cabinetry and bed heights around those shapes. A house AC adds weight up high; be mindful of total payload and roof rail ratings.

• Warranty and guidelines: Vehicle makers publish upfitter guides with roof cut locations, wire routing zones, and load limits. Respecting those drawings protects safety systems and keeps serviceability intact.

How both systems work together on the road

A practical way to look at the pairing is by trip phase. While driving in the heat, the factory rear AC can blast cool air to the back quickly because the engine supplies significant power to the compressor. That keeps passengers comfortable and lowers the thermal load on interior materials. As you approach camp, you can ease the cabin temperature down. Once parked, switch to the house AC for quiet, steady cooling that does not depend on idling.

Set control strategies that make sense for your routine. Use the vehicle climate controls for travel and the house thermostat for overnight. Keep vents unobstructed and avoid closed compartments that trap heat around appliances or batteries. Good insulation, window coverings, and thoughtful airflow paths will reduce the workload on both systems and extend run time off the battery.

Electrical architecture basics

A dependable house AC plan starts with energy math. Calculate expected overnight runtime and ambient highs, then select battery capacity, inverter rating, and charge inputs to support that demand. Shore power gives you unlimited runtime at campgrounds. When off grid, solar can help with daytime duty cycle but is rarely enough on its own in midsummer. Alternator charging during drive days fills the gap.

Fitment and layout constraints

Keeping the factory rear AC means the existing ducts, headliner contours, and sometimes side panels remain. Those shapes influence ceiling height, cabinet depths, and bed positions. If your layout calls for a continuous ceiling or tall upper cabinets, account for these components early to avoid airflow blockages.

Safety and service access

All electrical work should maintain proper fuse protection, wire sizing, and clean service loops. Leave access for filter replacement, condensate inspection, and roof fastener checks. Maintain clear separation between vehicle systems and house systems so future service is straightforward.

Pros and tradeoffs of keeping both

• Pros

  • Redundancy in extreme heat and during long trips
  • Faster pull down while driving using engine power
  • House AC can stay optimized for quiet overnight comfort

• Tradeoffs

  • Space taken by factory ducts and components
  • Added roof weight and height from a house unit
  • Extra complexity requires careful planning and professional integration

In practice, the decision comes down to your travel pattern. If you often haul people during hot daylight hours, retaining the factory rear AC is compelling. If your build prioritizes a clean ceiling and maximum cabinet space, deleting the factory rear unit opens room but removes redundancy. A balanced design can keep both and still deliver a tidy interior when planned from the start.

How OZK Customs designs balanced cooling that just works

We design climate systems around how you actually travel. That begins with a usage model, not a parts list. Our team maps your expected climates, drive time, overnight goals, and storage needs, then engineers a dual system plan that preserves the factory rear AC and adds a house AC sized for your lifestyle. We route condensate thoughtfully, select quiet mounts, protect roof structure, and tune charging so your battery plan matches your real nights, not ideal math. The result is steady comfort on the road and at rest, without surprises.

Explore what we build for adventure travel and see where your van can go next:

• Explore recreational vans
• Custom van build options
• Finance friendly vans

Ready to plan your cooling system. Tell us about your platform, climate goals, and travel rhythm. We will spec a house AC that complements your factory rear AC and integrates cleanly into your build, then hand you a van that stays comfortable wherever you park. Submit the form and let us draw up your path to calm, cool nights.