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No drier replacement, no compressor warranty!

By Richard Hawkins, MACS contributor

Read the warranty information of just about any new automotive air conditioning compressor and you will find verbiage addressing drier replacement very similar to the following:

  • The filter drier or accumulator must be replaced.
  • All compressor warranty requests must show proof of purchase of an expansion device, drier and approved flush.
  • To avoid a compressor warranty from being denied, the installer must replace the drier or accumulator.
  • Always replace the receiver drier/accumulator and expansion device to validate your warranty.  
  • To qualify for the compressor warranty, the receiver drier or accumulator and expansion valve or orifice tube must be replaced.

The wording is slightly different in each, but the meaning is the same.  Compressor manufacturers and parts distributors are adamant about driers being replaced when one of their compressors are installed. No drier replacement, no compressor warranty!  Yet, the people who sell A/C parts report there is often some resistance encountered with customers when the subject of drier purchase and replacement comes up. NOTE: This also includes driers which are designed to use replacement desiccant bags.

Forfeiting a warranty is a compelling reason to purchase and replace a drier, but let us take a look at three technical reasons to do so:

1. Desiccant moisture absorption capability.  Depending on the system design, most receiver driers contain about forty grams of desiccant.  Accumulators might contain upwards of eighty grams.  According to an industry provider of desiccant, the desiccant used in automotive driers can absorb about 21% to 23% of its weight in moisture when it is fresh right out of the manufacturers oven.  Some of that absorption capacity is lost in the packaging process, the manufacturing process of being placed in a drier, and finally the drier being installed on a vehicle.  The desiccant manufacturer estimates that the absorption capacity is down to about 18% by the time a drier is installed, and a vacuum is pulled on a system. This reduction is due to desiccants ability to suck moisture right out of the air.  Please see picture #1.

Picture #1: Desiccant such as what might be found in a typical mobile A/C system drier.

Doing a bit of Googling indicates that one US teaspoon will hold 4.93 grams of water. Eighteen percent of 40 (grams) = 7.2 grams, so the average size receiver drier has a moisture capacity of just over 1.5 teaspoons of water.  A larger accumulator would have moisture capacity of just over three teaspoons of water.  As you can tell, this is a small amount of moisture.  It seems hard to imagine, but moisture has the ability to gradually permeate through the hoses used in A/C systems.  I have heard about it in training sessions that I have attended over the years, but I wanted more information.  

As a result, contact was made with a hose manufacturer and they provided an SAE specification for moisture permeation.  It is J2064 and specifies < 0.039 grams of moisture per CC per year.   That does not tell us how much moisture might get into a system per year, but it does verify that moisture ingression and permeation does take place.

When a drier has been in use on a system for a number of years, there is a  possibility that the desiccant may be close to its moisture capacity.  Also, when a system is taken apart for service, the desiccant in the drier will be directly in contact with moisture. Those two things are compelling technical reasons to replace a drier. Please see picture #2.

Picture #2: A/C hose moisture permeation information.

2. A normal amount of compressor wear occurs even when a compressor replacement is not due to a catastrophic failure. If there is a catastrophic failure, there will likely be a huge amount of debris. The filter in a receiver drier traps this debris and if enough is present, the drier can become restricted.  This is a compelling reason to replace a drier.

3. A drier can easily hold 25% to 30% of an A/C systems oil capacity.  If the oil is contaminated, then that means that easily a fourth or more of the A/C system oil will consist of old contaminated oil if a drier is not replaced when replacing a compressor. Most people won’t do an engine oil change without changing the oil filter for the same reason, but yet they might leave an old drier on a system.

Picture #3:  Cutting this accumulator open revealed some badly contaminated discolored oil. As accumulators might typically hold about 3 ounces of oil, this could represent well over 25% to 30% of the total oil amount in the system.

Check back in next week and we will continue our discussion of driers and explore a myth that is sometimes associated with driers.

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