[eyknough]

Karl, thanks for that info.

I'm among the majority of vehicle owners with a/c who have to top off their systems regularly. I have a couple of suggestions, however.

When the a/c system leaks refrigerant, oil leaks as well. The exact formula for how much and when to add oil is not exact (since all leaks aren't in the same place and same size). But continually adding ONLY refrigerant will eventually leave your compressor starved for oil.

I have heard that approximately 1 ounce of oil per "pound" of refrigerant replaced is about right. That sounds like a bit much (especially for an evap leak). But I suppose it's better to have too much than too little. At least, I'd pay close attention to how the compressor sounds. If it starts making any noise (mine is virtually silent on my '94 caravan) I'd add an oil charge in short order. (The little cans add 2 oz. of oil and 2 oz of r-134a).

I strongly suggest getting a pressure gauge that hooks up to the high side ($16 at Meijers here in town). While it's good to monitor low-side pressures for best cooling, it's critical to monitor high-side pressure as well. Factory r-134 systems and legal r-12 to r-134 conversions will have a high side safety cutoff switch (that shuts the compressor off at a little under 400 PSI!!!). Any higher and you're going to blow the safety relief valve in the compressor.

Keeping the low side in the green while charging is not necessary (that gauge is more accurately interpreted while there is no refrigerant being transferred from the can to the system). The gauge that's in-line with the charge can will experience higher pressures while the hose is transferring refrigerant. The low-side of the a/c system is designed to handle way more pressure than you will produce with charging (as gas) with the valve wide opened.

Since it's recommended to only charge r-134 as a gas (can upright) it will take much longer to charge. Be patient. If you want to hurry the process, shake the can a few good shakes about once a minute while charging.

I maintain several a/c systems for myself and family and friends and I actually charge r-134 as a liquid. Never had one bit of trouble. I always have a gauge on the high side and I hold the can in my hand while charging. Monitor the high pressure while you (basically) pour the liquid in. Just watch the pressure on the high side and stop pouring when the pressure approaches about 320-340 psi (but continue to charge as gas) When the pressure drops, 'pour' in some more liquid. It dramatically shortens the length of time for the can to be empty. (Plus you end up with nice cool hands when you're done).

Get r-134a while you can.... By about 2020 I'm sure the epa (along with money from DuPont) will have r-134 determined to be too dangerous for our planet to endure. Oh... and the patent will have run out too for DuPont. :lol:

 

[eyknough]

Oh. I forgot... lol

If you absolutely can't get it to charge as a gas, and you're nervous about charging as a liquid with the system running.....

I have gotten entire cans of refrigerant in to a system that was not even running at all. It took about 5 or more minutes, but if you leave the can upside down, the liquid will work it's way into the system. A good shake about once every 30 seconds will help the process.

I'd be sure to measure the high side pressure (with the system running) before you add refrigerant like this. You want to make sure it's actually low since you're probably going to put in an entire can without monitoring any useful pressure readings (since the system won't be running).

 

[eyknough]

Shawn, if your system is cooling fine then don't add a thing. Some times when the system has not needed to be charged you might cause a small leak to start if you hook up the can tap (or even pressure gauge) Well... If it was going to leak, it'd be after you removed the charge hose. Not all systems need topping off every year. My brother has a 12 year old truck with original r-12 system that he hasn't touched at all and it'll freeze you out.

Thanks for supplementing my post, 94grand. I am not the most experienced person in the world and it sounds like you know more about what you're talking about.

However I do have a question about the oil compatibility issue you bring up. AFAIK, the oils can be mixed in any combination, but r-134a will only carry PAG or POE. The harm comes when r-12 (from a "converted" system) mixes with PAG oil. You do not want r-12 mixing with pag. Other than that, the POE oil says it's compatible with both retro-fitted and original r-134a systems (which come with pag from the factory).

I understand that auto a/c systems are supposed to be charged as a gas. R-12 cans say they are to be charged as liquid, though. Sure, r-134a is higher pressure than r-12, but I think if you pay enough attention to the high side pressure you will not hurt the compressor any. For a couple of years I used to charge r-134a as straight liquid, with my hand opening the throttle some to suck it in REALLY fast. The systems are still working now over 8 years later.

Most people who charge their own a/c systems are using about a 1 foot long hose. Not much room for a container of water under the hood. It's worth a try if it's faster than shaking the can, but I'm happy with the speed of charging as a liquid while monitoring pressure on the high side.

Stay cool!

 

[eyknough]

a 1989 will have come with r-12 from the factory.

An r-12 system properly converted to r-134a will have adapter fittings screwed to the charge ports. An r-12 system's charge ports look like tire valves. An r-134a system has quick-connect fittings just like those used for shop air compressor hoses. (where the air hose connects to the air supply line... not where it connects to the tire valve!)

If you are considering converting your system you should check out www.aircondition.com . They have a discussion forum where you can read up on the do's and don'ts of converting. The conversion kits sold at Wal-Mart have misleading directions. Many r-12 systems have a substance in their dryers / accumulators that disintegrates in the presence of r-134a, which will make your system stop working and will make it MUCH more expensive to get up and running again.

 

[eyknough]

94Caravan.... I believe you've just changed my mind.

I figured the liquid would just be squirted out the "out" valve with no harm done. (I swear the r-12 can I just bought said to charge as a liquid... which I thought was weird knowing that it's recomended to charge as a gas only).

Guess I'll look for a longer charge hose (or build in a nice can holder on to the hot tank on the radiator).

Thanks (says my a/c systems and myself)!

 

[eyknough]

Nope. It was r-12. Had to whip out my certification and all.

I'm pretty sure the can is still hanging around. I'll just have to take a look at it the next time. Heh. It was probably freeze-12 with an r-12 label put over it.

I know it's easy to be blas? about venting refrigerant. But just don't get caught or turned in. It's a HUGE gigantic humongous no-no in the a/c profession.

One violation is a career breaker if you're busted. It's probably harder to prosecute a non-certified person, but I bet the epa would make your life unhappy if not fine you outrageously even if you are not certified to make an example out of you.

The power of the DuPont lobby.

$100 for a top off? Yes... you were paying too much.

Hang in there.... unless you're in the southern hemisphere, it's ALMOST over...... Soon it'll be ice scrapers and kicking slush buildup off the wheel wells.

A one... a two....

ohhhhhhh the weather outside is frightful... but the fire is sooo delightful..... And since we've no place to go.... let it snow let it snow let it snow.

(Hey, nice new site setup! It's been a few days since I've been around)