Through different conversations with family members and friends, I have been told that it is good to apply a coat of car wax to the outside of the air conditioning unit frame. I assume that this is to maintain a protective seal and prevent corrosion. Has anyone done this before? I just bought a new Trane XR15 unit in April and I want to keep it in tip-top shape for as long as possible.

7 Answers 7


I have seen outside units whose paint has faded and become chalky-looking after several years of service. I suppose waxing it might prevent or delay this, but I agree with Doresoom that the benefit is really going to be mainly cosmetic.


I seems to me that waxing the outside of the AC unit is only going to protect cosmetic appeal. If you're interested in keeping the unit looking nice from the outside, then it could help. Otherwise, I wouldn't put in the effort.

  • Would waxing prevent corrosion? I assume you want the frame looking best to preserve the life of the unit. Jul 29, 2010 at 3:25

If you do this, make sure you don't get any wax on the coil! Doing so would hurt the unit's performance.

As others have said, this is totally a cosmetic thing. It won't help the life of the unit much. When the unit needs to be replaced, it will be because the coil or compressor is busted (probably 15yrs from now), and you've decided it isn't worth repairing. It's not going to need replacement because the frame has some surface rust.


The Trane unit has a special coat of paint that will make it look good for years and years, I doubt you will need to wax it.

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See Page 5 of the Trane informational packet:.

  • Ok, makes sense so they apply a powder coating. Jul 29, 2010 at 14:50
  • Even if it is powder coated, it could still rust. The odds of this are slim though, as it would have to be knicked in a spot to start to rust.
    – Evil Elf
    Nov 22, 2011 at 18:28

I've never heard of this before. Does it mention anything about doing that in the maintenance guide for your unit? If not, then I probably wouldn't bother.

  • I didn't see it. It was mentioned second-hand as word of advice from an air conditioning repairman. Jul 28, 2010 at 20:08

This will decrease your capacity and efficiency

As stated http://www.ccacac.com/maintenance-tips/tips/maintenance-homeowners-can-do/ it talks about just weeds, and dirt much less a thick coat of wax.

  1. Keep your outside unit clean and free of debris and plants. Grass clippings and vines can clog the outside coil and restrict the airflow. This will decrease your capacity and efficiency. Make sure that bushes and shrubs do not grow too close to the unit and restrict the airflow. The air must be able to escape freely from the discharge of the unit. Any restriction in this area can cause the hot air to be recirculated back through the unit. This will make the unit work much harder and reduce the efficiency and capacity.

  2. Rinse the coil on the outside unit. This will clean the loose dirt, salt, and sand from the coil. Do not wash it with pressure, simply rinse it from the top down to let the dirt freely flow out. Washing it with pressure may pack the dirt into the center of the coil. Pressure should only be used from the inside out to push the dirt out the way it came in. Rinsing the coil should be done about once a month during the cooling season.

  • 7
    I have to disagree with this -- that document is referring to dirt & weeds blocking the vents on the outside of the unit or collecting on the coil inside. These are things that could reduce the heat transfer from the coil. A coat of wax on the outside of the unit isn't going to have any effect on air flow or heat transfer. Note that we're not talking about a "thick coat of wax" but a very thin coat of wax -- if it's applied as you do on a car, almost all the wax is wiped off after it's applied. Jul 29, 2010 at 2:49

I'm assuming you're talking about the condensing unit sitting outside?

I'd say you'll wear out the unit long before the frame becomes damaged enough to affect it's function.

  • Yes, the condensing unit outside. As an aside, the air conditioning repairman said keep corrosive chemicals such as pesticides and fertilizers away from unit as well Jul 29, 2010 at 14:48
  • He probably said to do that because corrosive chemicals can get on the coil (the "radiator" behind the grates in the outdoor unit). A corroded coil will leak, and a leaking coil is often a >$1000 repair! Aug 2, 2010 at 20:41

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