receiver dryer "reuse" question

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receiver dryer "reuse" question

Postby Jeffrey3000 » Tue Oct 04, 2005 10:09 pm

Is it possible to pull enough vacuum on a "closed" A/C systems receiver dryer to dry the desiccant out enough for reuse? This should be feasible - has anyone calculated or attempted this? Also, can the receiver dryer be removed (cartridge type) and heated in an oven to dry it out?

I am using an "extra strength" Vacuum Pump (a Varian 2 stage used to rough Turbo & Cryo pumps) to evacuate the A/C system on my 1989 Toyota pickup truck (340kmiles). I had the evaporator out for a few days while leak testing it, and covered the suction/liquid lines at the firewall with tinfoil (should've done better job capping it). Finally found a failed O-ring, replaced it and other O-rings, re-assembled system, and pulled an 8-hour vacuum. Back filled with Nitrogen (dry, high purity), and after 8 hours have lost 4 pounds of pressure. Plan on pulling another 8-hour vacuum, re-charging with R-12, and hoping that the UV dye I have added will find the "undetectable" leak. Possibly the R-12 molecule will be too big to leak as the Nitrogen has slowly done. Can I do a few more "fill/pump" cycles with the Nitrogen to dry out the receiver?

Any useful information is greatly appreciated. Thanks!
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re-using driers

Postby Nacho » Tue Oct 04, 2005 11:59 pm

Most of them are so cheap, is not worth the risk. You can look up your Toyota's drier at http://www.acsource.net.
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Postby Jeffrey3000 » Wed Oct 05, 2005 12:33 am

Already purchased a new one from the dealer at $38.00- (with tax). The one I have on presently is only a few years old - hoping to maybe reuse it. I wonder if the one you recommended at "acsource.net" for ~ $14.00- is an OEM cartridge type that will fit my OEM billet aluminum mounting block with sight glass? Anyhow, will probably install a new one. What do ya thing about my 2 pound per hour Nitrogen leak - do you think it will hold R-12, being that R-12 molecules are much larger and denser than Nitrogen? Thanks!
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Toyota drier

Postby Nacho » Wed Oct 05, 2005 2:18 am

Yep, it is exactly the same.

About the loss, never trust a loss rate based on molecule size. To me a leak is a leak and you should have it throughly checked before pouring some precious R12 in there.

Dealer items are generally the same as most independant retailers but generally much more expensive. Dealer is our last resource.
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Postby DNT » Wed Oct 05, 2005 2:24 am

The only reliable and easy way I have found to identify tiny leaks is to add a few ounces of R22 along with your nitrogen and pressurize to around 150 psig then use a Electronic Heated Pentode refrigerant leak detector such as a TIF ZX1 you can easily pinpoint the leak in this manner reliabally and without delay. Some people prefer other methods I am just relaying what works for me.
Timing has a lot to do with the outcome of a rain dance.
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Re: receiver dryer "reuse" question

Postby test specimen » Wed Oct 05, 2005 2:51 pm

Jeffrey3000 wrote:Is it possible to pull enough vacuum on a "closed" A/C systems receiver dryer to dry the desiccant out enough for reuse? This should be feasible - has anyone calculated or attempted this? Also, can the receiver dryer be removed (cartridge type) and heated in an oven to dry it out?

I am using an "extra strength" Vacuum Pump (a Varian 2 stage used to rough Turbo & Cryo pumps) to evacuate the A/C system on my 1989 Toyota pickup truck (340kmiles).

Any useful information is greatly appreciated. Thanks!


The short answer is NO.

You don't have enough vacuum, even with the two stage pump. You would need the turbo pump to remove the moisture from the desiccant. The molecular sieve desiccant will release water when the partial pressure of water vapor above the desiccant is lower than the partial pressure of moisture inside the desiccant. To reactivate the desiccant you would need to reduce the pressure to less than 10 microns for as long as it takes for the water to migrate out of the sieve (hours / days?). The recommended procedure from UOP (who makes the sieve) to regenerate the desiccant is to heat to 600 degrees F and pass dry nitrogen through the drier for four hours. If you overheat the sieve, you will destroy the crystalline structure of the sieve and ruin it.

Buy a new drier and toss the old one in the garbage.
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Postby Jeffrey3000 » Thu Oct 06, 2005 1:14 am

Thanks "test specimen" and all other for your responses. Hate to toss a few year old receiver dryer, but what the heck! Your info is pretty much what I believed would be the case.
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