How long can the AC drier be open before it's shot? - PeachParts Mercedes-Benz Forum

Chad300tdt · #1 07-22-2009, 10:18 PM

I'm flushing the AC system in my TD tomorrow and need some advice.

Should I leave the drier capped until just before the R12 charge or can I make all the connections and take it to the garage where it will be charged.

How long is too long for the drier to be open without getting the system charged with refrigerant?

Matt L · #2 07-22-2009, 10:20 PM

Unless you can charge the system with oxygen-free nitrogen, leave the dryer disconnected and capped until you are ready to pull a vacuum. It comes charged with nitrogen. ANY exposure to air is too long.

How do you know that you got too much water in the dryer? You find out years later when the acid formed eats through your evaporator.

kmaysob · #3 07-22-2009, 10:20 PM

you will be fine connecting it all up

kmaysob · #4 07-22-2009, 10:23 PM

Quote:

Originally Posted by Matt L

Unless you can charge the system with oxygen-free nitrogen, leave the dryer disconnected and capped until you are ready to pull a vacuum. It comes charged with nitrogen. ANY exposure to air is too long.

How do you know that you got too much water in the dryer? You find out years later when the acid formed eats through your evaporator.

BS a good vacuum will pull that little bit of moisture back out. if it really bothered you you could put a heat gun on the dryer for a few seconds while pulling a vacuum
and i have never seen one charged with nitrogen. infact, i have never seen one with caps tight enough to hold a charge.

Matt L · #5 07-22-2009, 10:30 PM

No vacuum will remove any moisture from the dryer, unless you put the dryer in a very hot oven. Your heat gun isn't going to help. The dryer is designed to hold that water, and hold it, it does.

But it's your car, care for it however you want.

There is a very slight positive pressure in the dryer. You may not notice it. If yours had no pressure, or if the caps were insufficient, complain to your supplier and not to me.

kmaysob · #6 07-22-2009, 10:38 PM

Quote:

Originally Posted by Matt L

No vacuum will remove any moisture from the dryer, unless you put the dryer in a very hot oven. Your heat gun isn't going to help. The dryer is designed to hold that water, and hold it, it does.

But it's your car, care for it however you want.

There is a very slight positive pressure in the dryer. You may not notice it. If yours had no pressure, or if the caps were insufficient, complain to your supplier and not to me.

i have never seen one with caps that will seal it that tight. that was both working for a parts supplier and a automotive shop. i guess we had better complain to fastlane too then. as the one in the picture has a plastic cap on one fitting and none on the other, or is it a display model?

leathermang · #7 07-22-2009, 11:04 PM

Chad, Kmaysob does not know of what he speaks...
Listen to Matt L.

kmaysob · #8 07-22-2009, 11:05 PM

Quote:

Originally Posted by leathermang

Chad, Kmaysob does not know of what he speaks...
Listen to Matt L.

ok, i guess i dont

Matt L · #9 07-22-2009, 11:12 PM

Sometimes the caps fit inside the fitting. That could be the case there, but in any case, yes, of course that is a display piece. They do not show you a picture of the part that they are about to ship to you.

You don't need much of a seal for this application. The pressure is about zero. The idea is to keep the air out, so as to keep out moisture.

If you have a dryer that has been sitting with no caps, do not use it. It is spent, and won't do the job.

The more time spent between installation of the dryer and evacuation, the more water the desiccant will absorb out of the air in the system. And, as I said before, you have no indication that the system is wet until you get leakage resulting from the acid formed in the system.

However, I will agree that you probably won't get much water in the dryer in most cases. It does come full of nitrogen and it's not like it's under a vacuum when you connect it to the lines, so it won't suck the air in from the system. But temperature changes (e.g., driving the car) will move the air around somewhat, and you have no idea how much.

leathermang · #10 07-22-2009, 11:29 PM

Quote:

Originally Posted by kmaysob

ok, i guess i dont

Thanks for being so gracious in accepting the fact...

compu_85 · #11 07-22-2009, 11:29 PM

Leave it open to the air for the shortest possible time. If that means installing it right before you pull the vacuum then do that

-Jason

kmaysob · #12 07-22-2009, 11:30 PM

ok, from what i gather, he is not talking about installing it and having it charged a month from now. he simply wants to get everything installed and tightened down before heading to the shop. yes i will agree that they all come with "caps" but i have never seen one with a cap that would seal so well that it would hold a nitrogen charge in. most accumulators have slip on caps and are just that, slip on, but lets assume that there is a Slight positive pressure in it, do you really think that its gonna stay for the 6 months or so that the part sits on the shelf? its been a while since i worked in parts, so to verify i called a buddy that still does. he said the same thing, they are not sealed tight enough to hold a nitrogen charge in

leathermang · #13 07-22-2009, 11:35 PM

The point is that the ability of the silica jell or pearl media under the oil in the receiver dryer to capture moisture is a one way function. If half its ability is used up before it is installed by not minimizing the open time then that half left is all that is available for conditioning the oil and refrigerant charge.
That media is UNDER oil and moisture can NOT be vacuumed out of it once attached.

kmaysob · #14 07-22-2009, 11:46 PM

Quote:

Originally Posted by leathermang

The point is that the ability of the silica jell or pearl media under the oil in the receiver dryer to capture moisture is a one way function. If half its ability is used up before it is installed by not minimizing the open time then that half left is all that is available for conditioning the oil and refrigerant charge.
That media is UNDER oil and moisture can NOT be vacuumed out of it once attached.

i can agree with the idea of shortest time possible. in the short time it takes to run to the shop is not gonna use half or even a quarter of the dessicant up. i belive it can be removed, but thats fine, i can admit the possibilty that i am wrong here. my biggest argument is on the new dryer being so well sealed that it will hold pressurized nitrogen. NOW, if we are talking a nitrogen "purge" i will call that plausible, but i will also argue that there is a great possibility that air has mixed in that purge.

whunter · #15 07-23-2009, 12:21 AM

Quote:

Originally Posted by Chad300tdt

I'm flushing the AC system in my TD tomorrow and need some advice.

Should I leave the drier capped until just before the R12 charge or can I make all the connections and take it to the garage where it will be charged.

How long is too long for the drier to be open without getting the system charged with refrigerant?

Make all the connections and take it to the garage where it will be charged.

Question: How long is too long for the drier to be open without getting the system charged with refrigerant?

The answer is variable with atmospheric and enviornmental conditions:
* Extreme humidity conditions (99%) require longer vacuum to remove moisture, the reverse is also true.
* Do not allow particles (dust/dirt/etc) into the system.

Do NOT worry yourself into an ulcer, a good vacuum pump will remove the moisture.

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Have a great6 day.