A/C Work Recommendation/Tip

Post by **Legacy777** » Sun May 31, 2009 6:52 am

I just thought I'd reitterate this to anyone looking to do any A/C work on their car. Make sure you have a deep vacuum pulled on the system for a minimum of 30 minutes. This will boil off any moisture that is in the system. It is also a good idea to replace the drier if you have the system open.

Moisture combines with the refrigerent to produce an acid. Besides that nastiness, the moisture can play havoc with the expansion valve and cause the compressor to cycle a lot.

I did this work today on the Impreza; replaced the drier, pulled a vacuum on the system, and charged it back up because the damn compressor was cycling every few seconds.

93forestpearl · Post by **93forestpearl** » Sun May 31, 2009 7:14 am

I need to do something about my beater wagon. It is holding refrigerant, but the relay goes clickclicklcikclcikclcikclcikc, clicklcikclcikc, etc. I'm thinking the relay wight be bad since I charged my sisters '95L and it clicked on right away without issue as soon as a lick of refrigerant entered the system. It will be a serious PITA though, without cracking open the system. There is a thermistor of sorts in the evaporator core that is wired as part of the relay. Damn....

Skruyd · Post by **Skruyd** » Sun May 31, 2009 11:00 am

Another thing on pulling vacuum on the A/C. After the 30 minutes of pulling vacuum. Leave a gauge on the system for at least 15 minutes while the system is still under vacuum. If you start to lose vacuum you are going to have to check for leaks. Also if you are still on R-12, it's a good time to change over to R-134a considering R-12 sells for about $50 a pint, or if you want a rolling ice box I suggest R-404a or R-507.

Note: R-404a and R-507 are not automotive grade freon. Use at own risk

Post by **Legacy777** » Sun May 31, 2009 3:07 pm

Good point Skruyd. I forgot to mention that. I have found though, that if there is a small leak, you won't be able to pull a deep vacuum. Found this out with a buddy's Mitsubishi Eclipse.

ericem · Post by **ericem** » Sun May 31, 2009 4:08 pm

With my 93 legacy had a tiny leak. Only leaked every couple of months. What my dad did was pull a nice vacuum as suggested and then we recharged the system with r12A refrigerant bottles you get at a automotive store and there stop leak additive. After 2 years the pressures are still the same and the compessor cycles as it should. The car has been sitting for 3-4 months and I started it up on a hot day recently, still blows ice cold and the compressor cycles normal still!

Skruyd · Post by **Skruyd** » Sun May 31, 2009 9:02 pm

ericem wrote:With my 93 legacy had a tiny leak. Only leaked every couple of months. What my dad did was pull a nice vacuum as suggested and then we recharged the system with r12A refrigerant bottles you get at a automotive store and there stop leak additive. After 2 years the pressures are still the same and the compressor cycles as it should. The car has been sitting for 3-4 months and I started it up on a hot day recently, still blows ice cold and the compressor cycles normal still!

You sure it had a leak? Not saying it didn't. Just saying because the A/C system is allowed to loose 1 oz. of freon a year. The capacity of the legacy for R12 is 1.8-2 lbs of freon. So that is about half the system is emptied giving it's age. Also make sure there are caps on the fittings. Those act as seals for the schrader valves if they ever start to leak.

Post by **Legacy777** » Mon Jun 01, 2009 1:49 am

Yeah, the schrader valves do leak over time, the Impreza definitely exhibited this.

n2x4 · Post by **n2x4** » Mon Jun 01, 2009 3:54 am

How are you "pulling a vacuum" on the system?

I ask because I just took my first crack at repairing an AC system from my usual approach of just yanking the entire thing out of the car..

Bought a recharge kit for my 99 Forester. Was able to identify a leak on the high side fitting at the compressor. Replaced the O-ring and recharged through the low side. AC works great now, but I'm wondering if there's something else I should have done before recharging it. It's been fine for a week now. I've been running the system a lot and checked the pressure and it hasn't dropped at all. I got it charged to around 30psi.

Post by **Legacy777** » Mon Jun 01, 2009 4:16 am

You need to pull a vacuum with a vacuum pump.

Doing you're own AC work is not a cheap endeavor. The air compressor venturi vacuum pumps don't pull a strong enough vacuum, and the electric vacuum pumps run around $200+. A good set of gauges will run around $150 - $200 from what I recall. I tried to get by with a cheap set, and the fittings caused me issues. Anyway, it's been worth spending the money on the vacuum pump & gauges. I've done my cars a couple different times, and a friends. The only real way to ensure a proper amount of refrigerent is to evacuate & recharge the system.

Anyway, if you opened the system up and have not pulled a vacuum, you will have air and moisture in there that will degrade the performance of the system, and as mentioned above, moisture and refrigerent mix to create an acid.

I'm not saying it won't work for a period of time....but you will probably have issues in the long run.

n2x4 · Post by **n2x4** » Mon Jun 01, 2009 4:39 am

Legacy777 wrote: Anyway, if you opened the system up and have not pulled a vacuum, you will have air and moisture in there that will degrade the performance of the system, and as mentioned above, moisture and refrigerent mix to create an acid.

I'm not saying it won't work for a period of time....but you will probably have issues in the long run.

I don't disagree at all. It was blowing hot air before, so I figured it couldn't get any worse. I don't think I introduced any more air to the system than it already had (who knows how long it's been broken) I'll have to see if I can find anyone with a vac pump. Where did you get yours from?

I tried searching online before I went to do the job and didn't find any decent info beyond "take to a trained professional". That's never stopped me before though

Post by **Legacy777** » Mon Jun 01, 2009 6:31 pm

I got mine from JC Whitney.

Here's the one I got

Vacuum pump

You also need a set of gauges. I got some similar to these.

http://www.sjdiscounttools.com/cpsma1234.html

vrg3 · Post by **vrg3** » Tue Jun 02, 2009 1:03 pm

Good advice, Josh. Another thing that I do is I run the engine and keep the hood nearly closed (just open enough to allow the manifold gauge hoses out) while I'm pulling the vacuum. I figure the extra heat will help boil the moisture out.

I built a vacuum pump out of two scrap refrigerator compressors plumbed in series. It's a decent way to pull a vacuum on the cheap.

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A/C Work Recommendation/Tip

A/C Work Recommendation/Tip