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Why Is My RV Air Conditioner Leaking Inside?

RV air conditioners are a god-send when camping in the heat – assuming they function properly. But if your AC unit is leaking, there could be a number of causes. If it’s leaking when raining, it could be a problem with the seal around your AC, rather than the unit itself, for example.

The most common cause for an AC leak is that the drain pan is not functioning the way it should. It could also be an overly loose or tight gasket, or a drain pipe being clogged. These are all relatively easy fixes, so don’t panic quite yet.

Here’s how to figure out what’s causing your RV’s AC to leak into your vehicle, and what to do to get the problem fixed.

Drain Pan Puddles

The drain pan operates with the drain pipe to clear water from the AC unit. This is where the collected liquid will sit until the pip clears it to the exterior of your vehicle. This fix is easier than the next one, in that it’s kinda part of the upcoming process – but don’t worry, none of this is overly complicated.

  1. Climb (carefully) to the top of your RV, where the AC unit is located. Pop off the cover(s) with a screwdriver and take a look inside. Is the evaporator coil or drain pan looking gross? That’s likely the problem.
  2. Give the evaporator coils and drain pan a quick clean, pop everything back into place, and boot up the AC unit. If it works, problem solved! If not, move onto the next tip.

Drain Pipe Problems

In short, the drain pipe for your AC does exactly what the name implies. It drains liquid from the drain pan to the exterior of your vehicle. If you’re opposed to taking the unit to a professional, here’s what to do to check if this is the problem.

Quick And Easy Fix

  1. As with all electronics, it’s extremely important to fully turn off the unit (and any additional connected power, like the RV itself). It doesn’t matter how frustrating that puddle in the bottom of your RV is. Do you really want to become the guy who electrocuted himself with an AC unit? No, you don’t. So turn it off.
  2. If the drain pan already has water in it, dump it. Then, check the pan for any plant refuse or other grime that may clog up the works.
  3. If the pan is clean, it’s time to check the drain pipe itself. Gently clean the inside of the drain pipe with a soft brush. You don’t want to cause further damage by aggressively scrubbing.
  4. Once this is done, flush the pipe with bleach (careful to not get it anywhere else). This will make it about as clean as you can get it and stop any gross algae or bacteria from growing in the pipe.

Gasket Spacing

The rubber gaskets for AC units function as a sort of seal for the unit to function properly on your RV’s roof. Since these are pretty flexible (by design), it’s usually up to the owner to install them. Meaning that things can go wrong if you’re not careful.

If the gasket is too tight, the liquid from your AC could get trapped inside of your RV. Too loose, and you’ve got an unwanted gap in your roof – obviously also not ideal.

Generally, the ideal spacing for your rubber gaskets is roughly half an inch. This is the “Goldilocks” distance that allows your AC to do what it does without leaving large gaps in the roof.

Additional Gasket Tips

If it’s looking like your gasket has lived past its prime, it’s time to replace that bad boy. This is a relatively easy fix, but it’s important to be aware of your limitations. You’ll have to climb on top of the RV, so be sure you’re up to the task. There’s no shame in asking a professional for help.

If you’re dedicated to fix it yourself (look at you, Mr. Handyman!) then here’s how to go about it:

  1. Protect your roof – Lay down padding, such as blankets, to protect the roof of your RV. You have to climb around on it, so make sure you’re not causing additional damage to the roof while doing this. Tie the blankets down if needed.
  2. Remove the unit – Pop off the shroud and remove the unit from the roof of your RV. Now, as I’ve said it before here, I’m assuming you turned it off. If you didn’t – don’t do this step. Now turn around, turn it off, and congratulate yourself on being a smart mechanic… on the second try.
  3. Old gasket off – Remove the gasket in question and strip all of your sealing putty from the area. This means actually getting all of the sealant off – not just calling it “good enough.”
  4. New gasket in – Now pop in your new gasket, replace the AC unit, and reapply sealant – carefully. Too much sealant can also cause your AC to leak. If the space that moisture should be escaping is sealed too tightly, it’ll go down instead of out. And we’re trying to fix that, aren’t we?
  5. Test – Now throw on the power and try to run your AC. If it’s working, great! If not, it may be time to swallow your pride and take it to a professional. There’s no point in wasting time on guesswork.


If you’ve followed all of the instructions listed here carefully, your AC leak should be fixed. If not, that’s a sign you did something wrong (it’s okay), or that there’s another problem you didn’t see. This is where you should be consulting people who do this for a living – after all, they get paid to do this.

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