RV Air Conditioner Leaks When It Rains

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One of the greatest fears with an RV is that the roof will leak on you. Damage to the roof is expensive to resolve and different solutions are required depending on what it’s made of.

In some situations, you may discover that the RV air conditioner leaks when it rains. Fortunately, it’s much easier to deal with this temporary problem than a serious roofing issue.

It’s important to isolate the leak and its true source. Only this way can you confirm if the trouble resides with the AC unit, its fittings, and seals, or the roof itself. It’s too easy to draw the wrong conclusion here and take incorrect remedial action.

So, read this article to diagnose it correctly and avoid wasting money.

RV Air Conditioner Leaks When It Rains

The common reasons for a Dometic air conditioner dripping water (or another popular RV AC brand) inside the RV, are as follows:

  • Mounting bolts are missing completely or worked themselves loose
  • The rubber gasket is faulty or broken
  • Shroud is damaged or missing
  • Roofing materials are damaged, or caulking has failed
Motorhome sitting on grass with picnic chairs outside

Now we cover these causes and what to do in each situation where the RV air conditioner is leaking into the RV interior.

4 Common Causes of the RV Air Conditioner Leaking When It Rains

#1. Mounting Bolts Loose or Missing

When the mounting bolts are too loose or have worked free and disappeared onto the road traveled, this could be causing the roof AC to leak water inside. It leaves a screw hole where water can access and reach the RV interior.

When the rooftop ac unit is leaking water, this is a frequent cause of it.

Get up on the roof and look at the AC installation setup. Visually inspect each bolt and check how tight they are. Note any bolts that are missing too.

Action to Take

Accessing the bolts is best done using a ladder inside the RV, not from the roof.

Take off the AC’s panel interior cover and inspect the bolts. Typically, there are three or perhaps 4 bolts in place.

Adjust the bolts one at a time. Do it gradually to ensure they aren’t excessively tightened and damage the bolt itself. Get a snug fit with the gasket, but don’t close the gap to nothing, because can break the gasket.

Once the bolts are resealed, the rubber gasket that surrounds the AC unit should improve the seal. Tightened sufficiently, a little bit of the gasket will still be visible. This is completely normal with under an inch of gasket observable once finished.

Read Also: How to Keep Moisture Out of RV in Winter

#2. Rubber Gasket is Faulty or Broken

The RV AC gasket provides a waterproof seal around the edges of the AC unit between the cover and the surrounding area. The seal is designed to prevent anything reaching the inside of the AC unit and water from finding its way down to the RV ceiling and below.

The tricky thing with the gasket is that it mustn’t be crushed down by the bolts to the point where it’s not visible. About half an inch or a bit more should be seen when properly fitted. This avoids the RV air conditioner sweating where condensation is getting stuck when the AC is operating, causing excess water around the seal creating a potential leakage.


Also, being rubber, the gasket can deteriorate with age. Wear and tear should be inspected by checking if the rubber has become hardened or is breaking off in the hands. This can lead to a split in the rubber with water penetrating the crack.

Note that if a gasket is cracked, it will undoubtedly allow water inside the AC unit when it rains. It may not be the only cause of water ingress, but it definitely is one of them.

Action to Take

Visually inspect all around the rubber gasket to check for excess compression, drying out, flaking, or cracks.

If you do find signs of serious degradation of the rubber, or a crack, it’ll be necessary to purchase a replacement rubber gasket, remove the AC unit, install the gasket, and then reinstall the AC unit once again.

It is also something that a qualified RV workshop can do for you. They can order the best RV ac gasket part and then book you in for an appointment in the workshop to fit it.

#3. Shroud is Damaged or Missing

The shroud covers the AC unit. It is designed to prevent debris from entering the functional space and clogging up the works. In addition to dirt, dust, twigs, and leaves, it also stops water too.

A broken shroud will eventually be a major cause of AC leaks. It’ll be necessary to get on the roof to visually inspect the shroud to confirm this. You’ll need to walk around for a close-up inspection to verify if this is another cause of water ingress.

Action to Take

When parts have broken off the shroud, the solution is to replace it completely. Any attempt to fix it otherwise is likely to only provide a temporary solution. The next major storm will remove any hotchpotch fix to an AC shroud.

Use Google to confirm the correct shroud cover for either the make/model or your RV or if the AC unit is aftermarket, then for that product specifically.

Read Also: Can I Use Flex Seal on My RV Roof?

#4. Roofing Materials Are Damaged or Caulking Has Failed

The last major possibility is an RV roof leak around the air conditioner. It can lead you to believe that the RV roof itself is helping to create water leaks inside the RV.

With the caulking, if it’s too high up, then condensation can pool below it, get inside the AC unit and into the RV. More caulking at a lower level can resolve this issue.

It’s also possible that water pooling around or near the AC unit could cause a water leak down into the RV. This could fool you into believing it’s an RV air conditioner problem. That’s even truer when water is leaking from near to the spot where the air conditioner is installed.

It is a low probability event that the roof has deteriorated, or roof damage is the cause of water leaks instead of the air conditioner unit. However, don’t rule it out entirely.

If recent damage or cracks are discovered on the roof near the AC, then it’s possible to use Flex Seal on the roof temporarily. This will help to seal it up before more permanent RV roof repairs. Also, if you haven’t sealed your RV roof in a few years, don’t be surprised to find it’s now leaking. The two issues could be overlapping here.

Action to Take

Inspect the roof for damage, paying special attention to the caulking. Look for damage or it being bitty and coming apart.

Take the time to look all around the AC unit area to see if any roof cracks or damage from a storm could be allowing water to ingress into the RV. If there is roof damage, maybe insurance will cover it.

How to seal around RV air conditioner? When the roof damage is found near the AC, this can be repaired using RV roof sealants. Also, if the caulking on the AC is too high, resealing at a lower position can prevent condensation build-up that gets into your AC system and down into the RV.

This Dicor Self-leveling sealant is one of the most popular for sealing and caulking:

Dicor Self-Leveling Lap Sealant – 501LSW-1 (4 Pack)

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It’s also possible to add either a shim or an additional gasket to increase the height of the RV unit above the water level on the roof. These steps can help to prevent future water from finding its way into the AC unit during a rainstorm.

Read Also: How Often Should You Seal Your RV Roof?

Closing Thoughts

A water leak through the AC to the motorhome floor only when it rains is likely caused by the mounting bolts, the rubber gasket, the shroud, or a roof issue.

There are other causes of RV air conditioner leaks such as a grubby evaporator coil, bad RV air conditioner drain tube, or blocked drain hole. However, these cause water leaks any time that the AC is running; not only when it rains. This is an important distinction to make when diagnosing an internal water leak originating near the AC unit.

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