Vacuuming and AC system. Do I have to?

[Thomas DeBusk]

Question about vacuuming an AC system: it was cracked open for several days with the ends of the hoses covered by electrical tape. No dirt entered, but all the freon evacuated, and I'm sure some atmospheric moisture got in. I've replaced the o-rings and connected it all back together.

Do I have to take it to an AC service center to have the system vacuumed before I re-charge it with freon? Does it matter if I re-charge with one of the newer refrigerants?

Thomas

[xj2fsj]

If your'e going to go thru the effort of getting the AC working again it would be foolish to not protect your investment by properly preparing the system for an upgrade. As far as the r134a goes I have heard mixed messages as to weather it works better that r12 so I'll reserve judgment till later.

[64Trvlr]

You need a new filter/dryer to start with. Then you need to rehook the hoses and evacuate the system. Let the vacuum pump run for at least 45 mins.
:cool:

[Thomas DeBusk]

"Evacuate"? With what? For 45 minutes? Is this an expensive piece of equipment only garages can afford? Or have I just not seen these at the hardware store before? Is it feasible for me to get one?

Thomas

[Stolen76]

Don't waste your money on the system without vacuuming it out. You need to hold a 27 hg vacuum for at least 15 minutes, preferably 30 minutes. What the vacuum does is pull the moisture out of the system and allows for a full charge of freon.
What happens if you don't.... water droplets will accumulate together causing the expansion valve to freeze up periodically (best case) or water droplets which get pulled through the system will hit the pistons in the compressor in liquid form and you will only get 1 season out of your compressor as liquid does not compress.(worst case)

As for the new refrigerants, make sure you empty the compressor of the old oil and refill it with ester oil before charging with 134a. Your new o-rings should also be coated with it. Replacing the filter/drier isn't an option if you change up to 134a. In all of the retrofits I have done, none have ever had a problem using the older expansion valve.

If you have access to an air compressor, pouring some rubbing alcohol in the lines and blowing clean dry air through them is also a big help. It gets all of the old oil deposits and trash out. Also, you can buy a $9.99 vacuum pump from harbor freight ! Check out Autozone, they may have loaner vacuum pumps.

In the long run, if you can't vacuum and charge the right way, you're better off paying to get it done, but they won't give you a warranty.

[64Trvlr]

A vacuum pump is about $200, so you might just want to take it to a shop and have them do it for you. AC needs to be done right and it does take some special tools, so you may be money ahead to have someone do this for you.
:cool:

[Ernzo]

HAd a similar issue. Replaced O rings, wondered if it was really 'fixed'. Took it in, $30.00 bucks to vacume out and check for leaks (holding vacume). At that time, I elected to have the shop add R12 and oil. Cost another 150.

Did you wet the O rings w/ mineral oil? Did you replace them all?

In order to goto r13, the dryer does need changing, although some have told me they did not and it worked.....but.....as '64 says, it is a fairly big deal, and much do-re-me can go down the drain if you skimp.

Plus, bad AC is not kool.

I ended up w R12, and I now add my own, but that is after I had the thing vacumed and tested 2 years ago.

IF the thing holds vacume and the compressor/clutch works, you are 3/4 of the way there, IMHMO