Tech Q&A: A/C Blows Warm Air on the Highway, a Solar/Battery Upgrade, and More

Our RV expert shares his insights and advice on a variety of topics. Got a question of your own? Send them to us at [email protected].

Hot Hot Highway Heat

Q: We have a 2023 Thor ACE 32B on a Ford F-53 chassis. The dash air conditioner blows warmer air when we’re on the highway. At idle, 40-degree air comes out of the dash vents. At highway speeds, the air hits 60 degrees—no difference when the A/C is switched to recirculate. Neither RV dealer nor Ford dealer can solve the issue so far. Any insight?

—William Taylor, Findlay, Ohio

A: This is a fairly common problem. The heater and A/C controls in the dash are operated by vacuum servos, which rely on engine intake manifold vacuum. When the engine is idling, it produces peak vacuum, and therefore the system works fine. Then, as the engine’s load increases, vacuum drops off. If there is any leakage in the hoses or other components in the HVAC system, there won’t be enough vacuum. The system will then default to Defrost mode and divert airflow causing symptoms like you describe.

The system needs to be diagnosed for vacuum leaks. It could be something as simple as a cracked or loose hose. Many well-equipped shops have smoke injection machines, designed to push smoke into the vacuum hoses and system. Smoke comes out, revealing the leaks. To ensure better operation, add a vacuum storage tank: Crown Automotive produces one. Also add a one-way check valve that when the engine is under heavy load it, doesn’t reduce the vacuum in the tank.

Towable Twofer

Q: I’m a longtime camper and never missed an issue of Trailer Life with your articles and columns back in the day. I am looking at adding to my solar array and changing to AGM batteries because of conventional battery maintenance issues. My favorite supplier has closed. Can you recommend another source?

—Ralph Spear

A: Absorbed Glass Mat (AGM) batteries don’t require refilling and do generally last somewhat longer than conventional lead-acid batteries. However, if you are a heavy user of solar power, you might want to consider switching to lithium. They last much longer, are much lighter and maintenance free and have more usable capacity for a given size. You can discharge them more deeply without damaging them. Prices have been coming down, and there are good used ones available at a substantial savings. Suppliers include RV Solar Concepts and Precision RV Service, We’d love to hear from readers about their favorite solar supplier.

Airbag Advice

Q: Is there a consensus on the use of air bags for trailer towing?

—Kathy and Cliff Andrews, Keizer, OR

A: I doubt there is any consensus—folks argue about everything. But air bags are a great addition to many tow vehicles. Without knowing the specific year, make and model and the make and model of trailer, or its approximate tongue weight, I can only provide generalities. It’s important for the tow vehicle to be fairly level when hitched up and towing. Stiffer rear springs could keep the rig level, but when you are not towing the vehicle might ride very stiffly.  Air bags allow you to add pressure when the trailer is attached and reduce pressure when not towing. Some kits even have onboard compressors with remote filling capabilities, so you can adjust pressure from the cab.

One important thing to remember: air bags should not be used to enable a vehicle to be overloaded. Never exceed the maximum gross rear axle weight rating or the tire ratings. Several companies manufacture air bags for pickup trucks. Kelderman Manufacturing, Firestone Airide and Air Lift are all well-known producers of air suspension systems, including those for light trucks. AccurAir Suspension also offers air suspension kits for various vehicles, including pickups.

Ask Us Anything!

Share your tech tales and send us your questions: [email protected].

This article originally appeared in Wildsam magazine. For more Wildsam content, sign up for our newsletter.