Your RV is sitting in a hot summer, and you want to know what to check before the heat costs you something. Here is the short answer. Heat goes after six things on every rig: roof sealant, tires, house batteries, the air conditioner, the fridge and the rubber seals. Check tire pressure cold on every travel day. Check the AC filter every two weeks in peak season. Walk the seals once a month. Keep the batteries charged and out of the sun. And get the whole rig into shade if you can, because shade protects all six at once.
Where you are changes the damage. Dry desert heat bakes and cracks. Humid heat does that too, then adds water. Both are below, with the full checklist at the end.
What does extreme heat do to an RV?
Rowley White RV, a Phoenix dealer, lists the damage in one line. Prolonged heat above 100 degrees raises the risk of tire blowouts, shortens battery life, cuts air conditioner efficiency, strains the refrigerator, dries out seals and speeds up damage inside. They also say a closed RV can pass 130 degrees inside.
Every item on that list has a maker behind it with a number.
Is dry heat or humid heat harder on an RV?
They break different things.
Dry heat goes after rubber and sealant. Rowley White names low humidity as one of the things that dries seals and rubber components, on top of the sun.
Humid heat goes after the inside. Airstream says relative humidity in an RV should be 60 percent or less, and that mold can begin to form colonies in 48 hours. The EPA puts the same line at 60 percent, ideally 30 to 50. In South Florida, the National Weather Service office in Miami says high humidity holds all summer, with dew points in the lower to middle 70s, from a median start around May 21 to an end around October 17. That is five months of air that wants to leave water on anything cooler than it is.
So a desert owner watches the roof and the tires hardest. A humid-country owner watches those too, and adds condensation, mildew and the AC drain.
Roof and sealant: check before the storm season, not after
Sealant is the first thing to go. Rowley White: “Over time, sealants can dry out, crack, shrink, or pull away from seams.” The roof makers put it on a schedule. Dicor suggests inspecting its DiFlex roofs twice a year and cleaning its Brite-Ply roofs at least four times a year. Alpha Systems says clean two to three times a year and inspect the caulking. Winnebago says twice a year, looking for cracks, soft spots, lifted seams and loose seals around vents, skylights, AC units and solar mounts. Lippert wants the seals around the roof, windows, doors and seams looked at monthly.
Pay attention to the air conditioner. Dometic’s installation instructions warn against any low spot on the roof where water collects, because standing water around the unit can leak into the interior. A puddle around the AC shroud after rain is worth a closer look.
Do the roof walk before your storm season starts. A seam that cracks in May leaks in July.
Tires: cold pressure, age and shade
Pressure first. The RV Industry Association says to check tire pressure every travel day before you leave, because it should only be measured with the tires cold. Michelin adds, “Do not reduce pressure when tires are hot.” A tire that reads high at 4 p.m. is reading the afternoon.
Then age. Michelin says tires in service ten years or more from the date of manufacture should be replaced even if they look fine, spares included, and that the five-year inspection and ten-year replacement guideline runs from the manufacture date whether the tire was rolling or sitting in storage. The date is on the sidewall.
Parked tires need shade. Goodyear’s storage bulletin says stored tires should be protected from sunlight and ozone. North Phoenix Storage puts it in plain terms: tire covers, or a covered space that keeps them shaded.
House batteries: the heat number that matters most
Trojan Battery: “For every 18° F (10° C) rise above room temperature (77° F or 25° C), battery life decreases by 50%.” Do the math on a battery living at 113 degrees and it is running at a quarter of its rated life.
Shade the battery compartment if you can. For storage, Trojan says to fully charge batteries first. Interstate says to check the water level and state of charge on flooded batteries every 45 to 60 days. Lithium is easier: Battle Born says its batteries do not need a trickle charge or maintenance while stored, and recommends charging to 100 percent and disconnecting them.
Rooftop air conditioner: filters, coils, voltage and water
Coleman-Mach says to clean the outside condenser coil at least once a year and to clean or replace filters as needed. Furrion is more specific for summer: “Check every two weeks in peak season.”
Watch the voltage on a hot afternoon, when every unit in the campground is running. Coleman-Mach says its units run safely between 105 and 125 volts and warns that running outside that range can cause serious component damage.
Humidity changes what “working” looks like. Coleman-Mach says a healthy unit blows air 16 to 22 degrees cooler than the air going into the filter, and that humidity is a big factor in that number. Dometic’s instructions say high fan on cool gives the best results in high humidity or high outside temperatures. Winnebago points out the AC is also a dehumidifier, pulling water out of the air.
That water has to go somewhere. The EPA says to keep AC drip pans clean and drain lines flowing. Dometic says moisture condenses on cold surfaces, so some sweating on the ceiling vents is normal, and keeping doors and windows shut cuts it down. Water running out of the unit is not normal. In the owner question in the FAQ below, it was a blocked drain and dirty coils. If it is cooling poorly instead of dripping, the AC not cooling guide goes step by step.
Refrigerator: expect less in July
An absorption fridge makes cold by moving heat out of the box, and hot air makes that harder. Dometic puts it this way: “In hotter climates during summer period, we would expect the temperature to be around the 32°C (95°F) boundary.” Its support page also calls venting, clearance and airflow “imperative.” Keep the outside vents clear, keep the rig level, and expect less from the fridge in July than in January. The refrigerator guide covers the four checks and the hard upper limits.
Slides, seals and awnings when storms roll in
Lippert says heat can soften rubber slide seals, adding friction, and that metal parts can expand enough to make a slide move sluggishly. Wet weather has its own problem: Lippert says wet conditions let dirt and debris collect along tracks and seals, which can keep the slide from closing tight. Clean the seals and check for debris before you move the slide.
Awnings take the worst of the afternoon storms. In West Central Florida, the Tampa Bay office of the National Weather Service says the rainy season runs from late May to mid October, and that hail, damaging winds and waterspouts are common early in it. The rule is the same everywhere: retract the awning when you leave the site. In humid weather, Lippert also says a wash helps rid the fabric of mold and mildew.
Water heater, fresh water and generator
Suburban says to check the anode rod every 6 to 12 months, and to drain the tank whenever the RV is not being used. Winnebago’s schedule: sanitize the fresh water system every six months. For the generator, Cummins Onan’s manual says to run it at least two hours a month at about half its rated load if you do not use it much. If it fights you, the generator guide is the next stop.
How to store an RV through a hot summer
Some of this is the same anywhere hot:
- Batteries charged and disconnected, or on a maintainer (North Phoenix Storage, Trojan).
- Fresh, gray and black tanks drained and flushed, and the water heater drained (North Phoenix Storage, Suburban).
- All food out, canned goods included, because cans can burst in extreme heat. Fridge and freezer doors propped open (North Phoenix Storage).
- Tires covered, or the whole RV under a roof.
- Roof vents cracked under covers that keep rain out, so the inside breathes and stays cooler (North Phoenix Storage). In an open lot with blowing dust, some owners seal them instead.
- A walk of the roof seams, so you know what you left.
In humid country, add the moisture steps. Airstream says to open closets, cabinet doors and drawers while it sits, and that a dehumidifier helps if you check its bucket regularly. Winnebago’s own writers keep moisture absorbers in the cargo bays when they travel somewhere humid. The EPA says wet spots dried within 24 to 48 hours usually do not grow mold.
In the desert Southwest: monsoon season
Arizona has its own storm calendar. The National Weather Service office in Phoenix says monsoon season officially runs from June 15 through September 30. The Tucson office says thunderstorm wind gusts in Arizona almost always exceed 40 mph, and that dust storms are more common early in the monsoon. Forty miles an hour is plenty to fold an awning.
So in Arizona the sun does the drying all spring, and the monsoon does the testing. Check the roof in May. Retract the awning from mid June on, every time you leave.
The checklist
Every travel day, cold tires only: tire pressure (RVIA).
Every two weeks in peak season: AC filter (Furrion).
Monthly: seals around roof, windows, doors, slides and seams (Lippert). Generator run, two hours at half load (Cummins Onan). Flooded batteries: water and charge every 45 to 60 days (Interstate).
Twice a year: roof inspection (Dicor, Winnebago). Sanitize the fresh water (Winnebago). Anode rod, every 6 to 12 months (Suburban).
Yearly: AC condenser coil (Coleman-Mach).
Humid weather, all season: inside humidity at 60 percent or under (Airstream, EPA). AC drain flowing and no standing water around the unit (EPA, Dometic). Dry any wet spot within a day or two (EPA).
Before summer storage: the storage list above.
Every five years: tire inspection. At ten years from the date on the sidewall: new tires, whatever they look like (Michelin).
Do it yourself or call a tech?
Most of this list is yours. Tire pressure, filters, battery water, the dehumidifier, storage prep and a seam walk from a ladder need no special skill. Do them in the morning, before the roof is too hot to touch and while the tires are still cold.
Call a tech when the check turns up something past maintenance. Soft spots on the roof, or sealant that has pulled away over a long run, point to a reseal and maybe more. The roof guide helps you size it up. An AC that keeps dripping inside after you have cleaned the filter needs its drain and coils cleaned, and that means going inside the unit. A fridge that fails all four checks or a slide that keeps dragging are tech calls too. The cost guide shows what that visit usually runs.
Your next step: tomorrow morning, before the sun is up high, check the tire pressure cold and pull the AC filter. Then look at the roof. If what you find is more than you want to fix on a hot roof, the techs below list roofs, air conditioning, batteries or refrigerators among the work they do.