Electric Vehicle Maintenance: A/C Desiccant Replacement

What is a desiccant bag? A desiccant is a hygroscopic substance, meaning it absorbs water. Think of those silica pouches inside a shoe box; the ones that say “do not eat” on them. They’re a desiccant and used to prevent moisture build-up during storage. Every vehicle on the road utilizes a desiccant inside the air conditioning system to remove harmful moisture. In gasoline vehicles the desiccant normally doesn’t require replacement, but it has become a regular service item on electric vehicles. Why’s that? In an EV, the air conditioning system is actually used to cool the battery and electronics as well! If the system fails, your vehicle may not be drivable.

Alberta automotive air conditioning repair.

Why does it need to be changed?

As mentioned above, the desiccant controls moisture inside your air condition system. Moisture is especially harmful to an EV A/C system for two reasons:

  1. Moisture inside aluminum parts causes corrosion, which leads to parts failure. Hybrid and EV air conditioning components under a lot of stress: For example, the air conditioning compressor usually runs all the time because it’s part of the motor/inverter/battery cooling system, whereas the compressor in a gasoline vehicle operates about 25% of the time. Hybrid and EV air conditioning components are also much more expensive. A belt-driven compressor on a gasoline vehicle typically costs between $300 and $1000, while a high voltage compressor often costs $3000 or more!
  2. As moisture builds up inside the system, it causes the refrigerant oil to become conductive. (The POE oil used in EVs is hygroscopic (meaning it absorbs water) and water conducts electricity, as we know.) Once the conductivity reaches a certain level, this can set a “loss of isolation” fault code in one of the vehicle computers, and the vehicle will be disabled.

One some electric vehicles, the desiccant also includes a filter that traps metal particles (from compressor wear, etc) that could damage other components. Replacing the desiccant on time will help prevent unplanned breakdowns and extend the life of expensive air conditioning system parts.

How often should it changed?

Different electric vehicle manufacturers specify different desiccant service intervals, ranging from every 3 years to every 7 years. You’ll find this information in your owner’s manual, or by asking one of our friendly, non-commission Client Advocates. Please feel free to contact us any time!

You’ll be happy to know that we make our maintenance recommendations in accordance with your vehicle manufacturer’s service schedule – we haven’t cooked up an overly aggressive in house service schedule like so many of our competitors have. Occasionally we will recommend certain services sooner, but only when our industry experience allows us to determine that the manufacturer’s service interval isn’t enough to protect from expensive failures. We don’t take our clients’ trust for granted and therefore won’t “over-sell” maintenance like some of our competitors.

Electric vehicle service in Airdrie, Alberta.
Chevrolet Bolt Owner’s Manual showing the desiccant due for replacement every 7 years.

Benefits of checking the refrigerant level:

As part of your desiccant replacement service, we will replace any refrigerant that was lost over the years, “topping up” your air conditioning system. Here’s why that’s important: Most hybrid and electric vehicles feature a variable displacement air conditioning compressor with adjustable output. A variable displacement compressor can mask a low refrigerant level by just working harder, to the point where a system could be only 50% charged but the driver doesn’t notice a difference in their air conditioning cooling. However, all of this extra work can take years off the compressor’s life and generates a lot of extra heat in the system. Recharging your A/C system will take a load off your compressor, and it’s part of the reason that most automakers recommend the desiccant replacement every 3-6 years.

Image Gallery: Electric Vehicle Desiccant Replacement