Why Your RV Air Conditioner Leaks When It Rains


If the air conditioner in your RV leaks when it rains, you are not alone. Leaks from the roof, whether from the air conditioner, or something else, are one of the most common RV concerns. Unlike problems like a flat tire or battery failure that can be easily fixed, fixing a water leak is a process of trial and error.

Photo ID 124755463 © Andrey Popov | Dreamstime.com

Why Does Your RV Air Conditioner Leak When It Rains? There are several common issues that could cause a leak around your air conditioner:

  • Gasket and bolts
  • Gap between unit and roof
  • Roof deterioration
  • Plugged drain holes
  • Dirty evaporator coil

Any leak needs to be investigated immediately so that water damage is minimized.

Water damage to an RV is obviously a serious matter. But unlike in a house where a visit to the attic usually reveals the source of the leak, there is no attic in an RV. That’s why you need to be extra vigilant. Let’s look at the most common culprits to help you determine what is causing your water leak and how to solve it.

Gaskets and Bolts

In order to seal your air conditioner to the roof, technicians bolt a rubber gasket between the unit and the roof. This gasket has a little give in it so that it seals the unit to the roof. The gasket is designed to last several years, but it does need to be replaced every few years. Cracking is a sign that it’s time to replace the gasket.

If the gasket looks good, then you need to check that it has not been over-tightened. An overtighten gasket creates small pockets that allow water to enter. The gasket should be ½ inch high. If the gasket is in good repair and not overtightened, then make sure the bolts are tight.

Again, they should be tight, but not too tight. The bottom of the air condition unit should not sit directly on the roof.

Maintain a Gap Between the Air Conditioner and the Roof

Almost all rooftop A/C units are designed to let the condensation drain out of the bottom of the unit. They sit inside a drain pan that collects the condensed water, and the drain pans have small gaps on the side to let the water drain out. If there is no gap between the unit and the roof, then the water in the pan will instead flow down, either into the air conditioner or into the wall.

For this reason, never seal that gap closed. The gap is not the cause of a leaking air conditioner. Instead, it helps keep the unit from leaking.

Check for Roof Deterioration

The next thing to check for is roof deterioration. This can occur because water has been leaking long enough to weaken the roof material. It can also be due to age. If the unit is sagging, then the condensed water will pool against the air conditioner unit.

To check for this, you’ll want to get a string. Pull it tight across the roof, from one side to the other. If the unit is sagging significantly beneath the string, then you’re going to have to find a way to raise the unit up some. One way to do so is by installing a second gasket. Another is to shim up the unit or build a small platform for it.

Make Sure Drain Holes are Not Plugged

Sometimes the drain holes get plugged up. If they are, the A/C will leak only when it is being used. A plugged drain hole is easy to spot and easy to fix.

If your unit is leaking only when it rains then it may not be the drain holes but it is still important to check they are clean.

Inspect the Evaporator Coil

Sometimes the evaporator coil becomes dirty. If this happens, the coil will create enough suction to keep the water from draining as it should.

The evaporator coil is located at the front of the unit while the condenser coil is located at the back. To access the evaporator coil you need to remove the cover from your air conditioner as well as the sheet metal shroud.

Vacuuming the coils may be enough to clean them our otherwise you can pick up a degreaser product such as Formula 409 to get off any other built-up gunk.

Look for the Leak Elsewhere

Unfortunately, if none of those fix the leak, then the problem is elsewhere. Here are some possibilities

  • Check for leaks elsewhere on the roof. The seams on the roof of your RV are likely culprits especially if they haven’t been resealed lately.
  • Look for cracks in the pan the A/C unit sits on. A crack would cause water to drain straight down instead of down and out.
  • Still not sure where the leak is? Get a product such as Leak Finder and test the area around the A/C unit. This is an excellent way to test for a cracked pan. but be warned it will make a mess.

Maybe It’s Just Normal Condensation

Ever notice how much hotter it feels when the humidity is high? To help provide the cooling conditions, A/C units don’t just cool the air. They also lower the humidity by removing moisture from the air. As this moisture is pulled outdoors, some condensation is formed. A few drops of condensation are expected. An increase in condensation could be due to higher humidity.

How to Inspect Your RV Roof

A leak is a sign that water has penetrated your roof somewhere. If you catch it early, the damage will be minimal. The longer it takes to discover the leak, the more water damage will occur. That’s why it’s a good idea to periodically check your roof. Follow these steps

  1. Assume that you will need some sealant, so find out what kind of sealant should be used for your vehicle. Don’t discover a leak? Now you have sealant when the roof leaks.
  2. Look at all roof seams, not just the ones around openings that were cut into the roof for roof or plumbing vents, air conditioners, and antennas.
  3. Investigate discoloration and soft spots. They can indicate water damage even though there are no visible cracks or gaps. Soft spots, in particular, can indicate water damage.
  4. Roof investigation goes beyond looking at the roof. Take note of other openings in the RV, such as the water heater and water fills and then look for signs of moisture or leakage around those openings.
  5. Don’t forget to check outside storage compartments for leaks.
  6. Check for delaminating, or the fiberglass separating from the sidewall. While standing at the front or rear of the RV, look for bulges or ripples. Fiberglass separating from the sidewall bears further inspection.
  7. Once you finish the outside inspection, it’s time to head indoors. Check for wallpaper that is wrinkled or discolored. Also, feel the interior walls around windows, doors, vents, or any other openings that were cut into the walls.
  8. Inspect the corners of overhead cabinets where the walls and ceiling meet. A leak where they meet can create soft spots or discoloration.
  9. If your RV has a bed over the cab area, be sure to check under the mattress as well as for soft spots or discoloration. Over the cab sleeping areas have a reputation for leaking.

Final Thoughts

If there is a way to get in your RV, water will find it.”

Mark Polk

Water is essential to life, but there are places we want water and places where we don’t. That’s why you want to periodically check your RV for leaks. Water dripping from the air conditioner, whether it is raining or not is a sign that something is wrong. Take time to check for the cause and fix it ASAP!

Diane Dee

Diane is a lover of all things travel. She and her young family wanted to explore North America from the comfort of their own home so they bought an RV. After fully rehabbing a 1994 Safari Trek, they set out to explore both Canada and the USA.

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