I asked this same question a while ago but the timeline has changed and I just want to double check. I assembled my A/C earlier this year and found the evaporator leaked after I got it assembled. The accumulator is (was) new, never run, never charged with freon, but has been exposed to the atmosphere now by changing the new evaporator and by being exposed thru the leak for a month and a half now, should this be replaced seeing it has been exposed or will sucking it down with vacuum for a long time make it usable?

 

My opinion you should be alright. It really has not been wide open to the atmosphere. When I replaced the engine in my firebird I had my system open for several weeks and recharged it and for 2 years now it has been cooling fine. Make sure you pull a good vacumn on the system

 

What I was always told back when I did this stuff for a living, was either 4 years in service or 4 hours open to the atmosphere, and the drier needs changing if you are working on it. Evacuating (vacuuming) the system will not remove moisture from the dessicant in the drier.
Depending on how long you had everything wide open you may be OK to re-use it. The system will probably work fine. If it was me though, I would change it.

 

I'd change it as well, I agree with the 4 hours. If it freezes up you'll have some problems.

Frank

 

Change it. They are cheap.

 

I personally would not change it. However, I would vacuum it down for an extended period of time, like overnight.

 

Change the thing, its function is to remove moisture from the air, and if you live in a humid climate, thats exactly what it will do. As said before, it is not that expensive, and it is good future insurance. When you get the new one, compare the weight of it to the old one. That will give you an indication of how much water it has absorbed, I think you may be suprised.

 

 

I just priced a dryer at AutoZone $16
Is it worth $16, ..... to not have to tear into your A/C system again ?
Replace it.
69VETT

 

Thanks guys, I did order one today. Its not worth having it give me headaches in the future.

 

Hopefully this is not too much off topic..

What is the shelf life of a accumulator/dryer? I have one in an AC Delco box. It has the plastic caps to close off the input/outut. However, I'd think that after all these years some water vapor has snuck in there. Can it be re-activated to ensure there's no water vapor in there?

 

I don't think a year or two would affect it as long it has the plastic plugs tightly fitted to both sides. I personally wouldn't use a dryer that sat for more than that, as the guys said, its so cheap that its illogical not to replace it with a new one, why do you need to bite the bullet?

 

You bring up a good point. I don't believe their is a shelf life for desiccant, but I think that most new dryers have some moisture in them anyway. I worked at Advance Auto for a few years and can remember looking at new dryers where the caps had been removed and just laying loose in the box. Also, I remember customers asking to see a particular dryer, remove the caps and looking inside for some unknown reason, and then saying it was the wrong one. So when you buy a dryer, you really have no idea of what you are getting.

To combat this problem, I have read/heard of putting dryers in an oven for a while (don't recall the temp) to dry out the desiccant prior to installation. What I do, though, is vacuum the system down for several hours, sometimes up to 12, which will remove all moisture from the system, including that in the dryer. That, of course, is assuming you have a good vacuum pump. The way a vacuum pump works, if you recall your high school science class of temperature/pressure relationships, is the lower the pressure, the lower the boiling point of a liquid. In this case, a good vacuum pump pulling a vacuum of 29.76 in. HG, water boils at 40 degrees F. The boiling of water turns it into a vapor at this temp., which in turn is sucked out of the system by the vacuum pump.

Manuals will tell you that every time you open a system, the dryer/accumulator should be replaced, which is the subject of this thread. However, these are "shop" manuals written for a/c shops. Such shops usually pump down an a/c system for only about 1/2 hour, due to time is money, which is not enough time to do the job properly.

A case in point to the longer pump down theory is a fully restored '67 Vette I used to own. I worked on the a/c system several times and never replaced the dryer, which was probably over 20 years old, as I would have had to remove the hood due to the lack of room to access it, and since the car had a $10,000 paint job on it, I wasn't about to chance damaging the paint. In any event, I never had a bit of trouble with the system that was the result of moisture. However, as stated above, the system was pumped down for extended periods of time after it was opened.

This is why I recommended above not replacing the dryer and just pumping the system down for a longer period of time. I would suggest this to you also rather than purchasing another dryer.

Hope I didn't put anyone to sleep reading this.

 

FYI, you can rejuevinate welding rod that has been exposed to moisture by baking it between 700 to 800°.

A/C vacuum pumps are rated by the amount of cfm they can pull and also the amount of vacuum they can attain.
Only the better pumps can get low enough to boil almost all the moisture out. It has nothing to do with the time involved, a lesser pump can't do it, no, matter how long it runs.
That is why a pro shop can evacuate rather quickly.

You must use a micron gauge (expensive) and get to around 700 microns to get the moisture out. Ordinary dial gauges just can't read this.

Just for fun, I always vacuum my own stuff overnight anyway.

 

All due respect, noonie, but you might want to do a little reading on the subject of evacuating an a/c system if you really think time is not a factor in the removal of moisture with a vacuum pump.

 

Been doing a/c for over 30 years. I'm a little beyond the Advance Auto thing.

You try and suck down to 700 microns.
The moisture boils out at 1500 microns.
You let the closed system sit for a minimum of 15 minutes and if moisture is still present, it will go back up to 1500 microns or above.
You repeat as necessary until it holds at much less than 1500.
A pump that doesn't have the micron reading will NEVER get there.

Air powered venturi vacuum pumps can't get there.
A lot of electric pumps that are not rated or not maintained well not get to below 1500 microns at all. Imagine holding a Geo Metro at WOT. Do you think if you hold it there long enough it will reach the top speed of a C6?
Time is not a consideration.You use the readings of a thermistor vacuum gauge or micron gauge instead solely, as the cfm's of pumps vary.
The needle width of a good set of coumpound manifold gauges roughly represents 1" of vacuum, so it is impossible to read with them.

If you need any more info, let me know.

 

Good post. I love it when someone actually knows what they are doing, instead of guessing.

 

I enjoyed reading this. If I ever vacuum my AC myself, I'll let it set in vacuum soak for a long time.

When you get down to a low vacuum, there aren't many air/water molecules left in the system. Due to Brownian motion at room temp, the molecules are all moving and bouncing off the internal surfaces of the AC circuit. Simplistically speaking, a molecule is not going to exit the system until it just happens to bounce into the oriface the vacuum pump is connected too. So when there's not many molecules left they have to bounce around for many hours until they just happen to hit the vacuum line orifice. Sort of like randomly bouncing a billiard ball of the edges of a pool table. It'll take a lot of random bounces for the ball to finally go into a pocket.

 

Interesting reading,isn't physics fun???

 

Well, it wasn't fun at all when I was in school!