Air Conditioning Service

Is it necessary to routinely replace the air-conditioning filter/dryer? If so, how often?

No. That’s only replaced if the AC system is opened for some reason.


In you are talking about the in-cabin air filter, yes, it should be replaced according to the maintenance schedule in your owner’s manual.

There are professional sources that say driers/accumulators should be replaced every 4 years. This is a subject the Forum has agreeded to disagree on. It is not a practice that I apply to my own car or ever insisted a customer do but the issue is out there,something about the material bag in the accumulator losing its ability to absorb any more moisture.

The A/C system is a closed system. If the system is charged and not leaking, additional moisture cannot get in. The only time to replace the accumulator/dryer is if the system were to be discharged. THEN, the accumulator/dryer should be replaced before recharging the system. Just discharging the system to replace the accumulator/dryer makes absolutely no sense, unless your mechanic needs to make a boat payment.


The system is not so fully closed as you think. There are designed leak tolerences,the engineers know that the system will leak. The idea replacing the dessecant bag in the accumulator is to halt the forming of damaging acid which will attack and cause damage to metals like the condensor.

Hmmmm. Let’s see. A typical A/C system is constantly under pressure. At rest, before the system is engaged, the system equalizes to about 100-120 psi. When running, the high side has pressures in the range of 250-350 psi, and low side has pressures of 25-50 psi. These are pressures in relationship with normal atmospheric pressures.

If a leak develops, or occurs ‘within tolerance’, then the natural effect will be refrigerant escaping from the higher pressure system, not moisture-latent air to enter the higher pressure system. This is simple physics.

And the effect of moisture in the system is simple chemistry. Why do you think there is a dessicant bag in the system in the first place? because the enginers know that moisture gets in the system.

Check out what the pros have to say about typical life span of the dessicant bag. You will have to read into the description of the function of the accumulator.

Probably to take care of any moisture/contaminants that may have been left behind during the installation process.

IMO, driers are not a routine replacement item.
Question though. If the system, even at rest, is hovering around 115 PSI then how does moisture enter the system in the first place? Atmospheric pressure is not near high enough to overcome even a leaking system with a partial charge.

The accumulator replacement falls under the same logic as buds replacement of 3 injectors with no problem “to be on the safe side”. The effects of acid created by moisture in the system can cost many times what a accumulator costs.

The, to be on the safe side rational is not one that is entirely foreign to auto repair. Like I said initaly this is a issue we choose to disagree on. I have presented some of the sources for my conclusions,I am just not pulling this out of my hat.

Oldschool, I have respect for most of your advice you’ve given on this website. Usually, the answers you provide are spot-on with the given problems posted here.

However, on this subject, I have to wonder if you read the links you’ve posted. For instance, at ‘’, I quote the following:“as a standard practice, accumulators or receiver driers should be replaced whenever you are replacing the A/C compressor.” And at ‘’, I quote “It is a good idea to replace the accumulator each time the system is opened up for major repair
and anytime moisture and/or debris is of concern.”

Neither site supports your contention that it is normal and best to replace just the accumulator as a preventative measure or as regular maintenance. Only when the system has been cracked open for other repair, or if there is evidence of other internal system problems.

Did you also read at the first site where it says it is proven that dessicant bags are saturated after 4 years?

Did you also read at the second site where it says if there is any doubt about a moisture concern to replace the accumulator just to be on the safe side.?

The first site said that, but did not recommend replacing every 4 years because of it.

The second site did mention concerns of moisture in the system, but this would cause problems within the system, like icing of the expansion valve or orifice tube. Such a fix would require discharging the system, and, as I and the article mentioned, replacing the accumulator then.

As a preventative measure, neither article mentions that at all, and I still say it is a waste of money.

If your dessicant bag can no longer absorb moisture isn’t that a good enough reason to replace the accumulator?

The receiver-drier must be changed each time a system is empty regardless of the reason for loss of refrigerant. It should also be changed every three years, because the desiccant pellets will break down and clog the expansion valve. This will in turn cause the system to become inoperable and May damage the compressor. This is a cut and paste from the site from the link given,there are more.

I think your trying to read between the lines and see something that is not there. The moisture your referring to is introduced when the system is charged up. Once charged and sealed, moisture can’t get in. The desiccant will remove the trace amounts of moisture that get into the system then, but loses it ability to after 4 years. So, if the system is ever discharged, replacing the accumulator is strongly advised. But, no where have I heard that the desiccant will release it’s moisture back into the system after 4 years. And, I’ve never heard of additional moisture getting into a system that is charged up.

However, moisture can be added to a system when it is being re-charged, or refrigerant added due to a leak. I believe this is when most people start having endless problems with the A/C system. The proper course of action is to find the leak, discharge the system, fix the leak, replace the accumulator, evacuate and re-charge. Most go for the short-cut of adding refrigerant with leak-stop, and hoping for the best. If they add moisture to the system then, and the desiccant cannot remove it, then they will have problems that way.

As I have stated the recommendation is based on a better safe than sorry rational. Even one drop of free moisture can cause erratic or degraded cooling. Irreparable damage can be caused by moisture in the system. Many other parts on the automobile are replace with even less of a reason. Why gamble?

My text indicates that even a closed but discharged system for any lenght of time should have its accumulator replaced.

I feel you dont realise the consequences of moisture in the system and the degrading affect on performance it will cause.

I’m not being argumentative at all. Just trying to understand how 1 Bar of atmospheric pressure could force water molecules into a system (normal one for example) that is pressurized to 8 or 9 Bar.

If an A/C system has moisture in it then it has to be because someone did not perform a thorough enough evacuation; the purpose of which is more to remove moisture than purge the air.

If the system has ever been down to a very low pressure (under a Bar) or has been opened I could see it.

4450 Did you look at the additional link I posted in regards to drier replacement recommendation every 3 years? It is up in the thread a bit.