Car AC recharge

  • Posted by a hidden member.
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    Jul 13, 2013 4:47 PM GMT
    Are you a DIY or "shop" guy?
    I have never done it before but watched a few youtube videos and it looks pretty easy...
    AC is weak right now and if I do it myself the worst that will happen is I have to go to the shop....if it works....save time and money.....still not the most mechanically inclined, so mixed feelings...icon_confused.gif
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    Jul 13, 2013 5:16 PM GMT
    How old is the car? Does it take R-12 or R-134 regrigerant? You only find R-134 on US shelves due to ozone concerns, and if you add it to an older R-12 system you can damage it.

    The actual process is fairly easy, but the steps must be followed exactly, with no rushing, or you can get a "slug" in the line that can damage the compressor. You also need to be able to differentiate the valve for the suction (low) side of the system, versus the valve on the compressed (high) side, when present. If your AC is still working a little then that's easy: low side lines will be cold, high side hot when running (watch your hands & loose clothing). You add refrigerant on the low side.

    I was trained as a Master Auto Mechanic, still sometimes recharge car ACs for friends.
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    Jul 13, 2013 9:14 PM GMT
    ART_DECO saidHow old is the car? Does it take R-12 or R-134 regrigerant? You only find R-134 on US shelves due to ozone concerns, and if you add it to an older R-12 system you can damage it.

    The actual process is fairly easy, but the steps must be followed exactly, with no rushing, or you can get a "slug" in the line that can damage the compressor. You also need to be able to differentiate the valve for the suction (low) side of the system, versus the valve on the compressed (high) side, when present. If your AC is still working a little then that's easy: low side lines will be cold, high side hot when running (watch your hands & loose clothing). You add refrigerant on the low side.

    I was trained as a Master Auto Mechanic, still sometimes recharge car ACs for friends.



    I'm pretty sure it ain't R-12.....

    There's only ONE reason anything would need freon and it is because it has a freon leak somewhere. First find the leak.
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    Jul 13, 2013 9:32 PM GMT
    JUST did mine last week, total cost, $15. I returned the gauge afterward. The dealership and even places like AMACO wanted $150 plus.

    1. Buy R-134a refrigerant (check to see if that is what your car uses).

    2. Turn the car on and put the AC on full.

    3. Find the Low pressure cap for your AC unit under the hood. Many times it will have an L on it. Remove the cap.

    4. The gauge that comes with the refrigerant can (or if you buy it separated) needs to be calibrated to the current ambient temperature. It will tell you what range of pressure you aim for while adding refrigerant.

    5. Attach gauge to can (if not already attached) and place other end on the L nozzle of your AC unit with car still running on full AC. Tilt the can up and down as you squeeze the trigger to add refrigerant. Every now and then release the trigger to see if the pressure has increased to the range it needs to be in. Don't overadd.

    6. Remove from L, cap the L, and do not remove the gauge from the can unless you are certain it is empty.

    7. To be safe, wear goggles and gloves.
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    Jul 13, 2013 9:46 PM GMT
    all of the above info is correct but you should also be aware of what it means when a car's A/C system "needs a recharge." Because the refrigerant system is sealed there is no way (when in good condition) for refrigerant to leak out. As a car ages or if there is damage, the metal hardlines that carry the refrigerant between the A/C core, condenser, compressor, etc. can develop tiny leaks at the joints or even in itty-bitty splits in the tubing itself, allowing refrigerant to leak out. In all likelihood, unless the car is literally an antique that you found in a barn somewhere, untouched for 50 years, your car's A/C system has a leak somewhere. If you plan on keeping the car for a few years you might want to have a reputable shop take a look at the hardlines.
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    Jul 13, 2013 9:49 PM GMT
    I miss the old days of freon a/c. My first car was a little 4-cylinder compact. Didn't have a lot of power, but it churned out ice cold a/c. So nice in the summer.
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    Jul 14, 2013 2:48 AM GMT
    Clarification: "Freon" is a registered trade name of DuPont for a number of halocarbon refrigerant products. It's more accurate, and definitely critical when recharging an AC system, to use the correct industry identification, like R-134a as used in modern cars, or R-12 as used in earlier cars.

    As for leakage, a car AC system undergoes much greater shock & stress than a static residential AC installation, or in refrigeration units like freezers and refrigerators. A car AC must contend with:

    - very high underhood temperatures
    - engine vibrations and road jolts
    - multiple disconnect joints in the lines, to enable car services
    - a rotational seal at the compressor input shaft to deliver engine power

    Static residential and refrigeration systems are largely sealed permanently, by weld or solder, with fewer disconnect sites prone to seepage. Therefore some slight leakage over the life of a car AC system can be expected.

    Hence my first question to Sporty: how old is the car? Not only to know what refrigerant to add, but whether he needs a leak check with a detector, indicated if this is a newer car (4 years or less). Anything over 4 years then a partial recharge wouldn't surprise me (he says it still cools). If it loses cooling again soon after the recharge, then yeah, he's got a leak.
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    Jul 14, 2013 3:03 AM GMT
    ART_DECO saidI was trained as a Master Auto Mechanic, still sometimes recharge car ACs for friends.


    I'm on my way over with the parts. Are we still friends? icon_wink.gif

    Seriously, though, I'll be performing this service soon. I was under the impression that the minute leaks in the system would be taken care of by additives in the refrigerant. Am I mistaken?

    I recall replacing all the [swaged, the bastards!] power-steering hoses in my car only to find the fluid continued to leak. Only now I couldn't see where it was leaking from. Added some leak stopper, and no more leaks.
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    Jul 14, 2013 3:08 AM GMT
    Im a automotive techniton of over 20 yrs and i work in a shop. If its still blowing "cool" at least you now its still working and just needs a "tuneup". If its not working at all, like blowing "hot" or same temp as outside, it either has a large leak or has bad clutch/coil on the compressor or other problems like the condensor fan not working. (some vehicles have a seperate condensor fan just for the a/c).
    Anyhow. Lets assume it still working. LIke others have said, you want to find the "low" pressure side which is normally the larger dia hose or lines and yes those lines get cold with condensation while its running but you will only see that if its working properly. The newer systems (non R-12) have 2 sized fittings on them and you cant screw it up as far as hooking gauges to them. on the gauge or service hose is blue in color and the High side is red. Attatch the hose to the low side before starting the engine. Once atatched, start car, put a/c on high "recirc" and charge from the can. If it has a gauge it needs to be around 35-45 (low side)and 150-200 on (high side) when fully charged. Those readings will only show that when your not charging, the pressure will shoot up on low side when adding freion, so you need to close the valve on the can and let it stable out to get the final reading. Usually a vehicle with just low on freon will take a whole can anyhow.
    Whatever you do, if your using a gauge manifold that has both hi and low gauges and a center hose (usually yellow) in color for attatching to freon source, DO NOT open the HIGH SIDE valve when charging. The pressure will go to the can of freon and blow it up in your hand...
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    Jul 14, 2013 3:26 AM GMT
    shortbutsweet said
    ART_DECO saidI was trained as a Master Auto Mechanic, still sometimes recharge car ACs for friends.

    I'm on my way over with the parts. Are we still friends? icon_wink.gif

    Seriously, though, I'll be performing this service soon. I was under the impression that the minute leaks in the system would be taken care of by additives in the refrigerant. Am I mistaken?

    I recall replacing all the [swaged, the bastards!] power-steering hoses in my car only to find the fluid continued to leak. Only now I couldn't see where it was leaking from. Added some leak stopper, and no more leaks.

    Partly true, IF you use a refrigerant that has optional leak-stop additives. The pure refrigerant itself will not plug leaks.

    And the use of leak-stop in a car AC is controversial. Some contend it reduces the cooling efficiency, for various chemical and mechanical reasons, and may shorten the overall life of the system. In an older car that you don't intend keeping much longer this debate may be a moot point. In a car that's a "keeper" you should try to find & repair the leak without resorting to additives. And that's true for engine coolant systems as well.
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    Jul 14, 2013 3:39 AM GMT
    davidingeorgia said
    Whatever you do, if your using a gauge manifold that has both hi and low gauges and a center hose (usually yellow) in color for attatching to freon source, DO NOT open the HIGH SIDE valve when charging. The pressure will go to the can of freon and blow it up in your hand...

    If he's using a home charging kit it likely consists of a single hose, valve and fitting, rather than a full professional manifold. And as you say, it should only be able to connect to the low side. But I agree, tapping into the high side with an R-134a can is VERY, VERY bad.

    I miss the days when there was a sight glass on the receiver/dryer, and you could look for bubbles and at least make a ballpark estimate of the charge condition. I understand such things could be more trouble than they were worth in the hands of the untrained, but at the same time I see a trend to make automotive maintenance the exclusive domain of the dealerships, and less accessible to anyone else.
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    Jul 14, 2013 3:50 AM GMT
    Most R-134 recharge kits have a stop leak additive in them. After a while every car needs a recharge. It's quick. Just make sure you've checked out where the location of the valve is, and don't put too much in the system.
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    Jul 14, 2013 4:07 AM GMT
    I did it myself today! Went to the Autozone and got a can of ACPRO and followed the instructions...in the video....WOW it was easy and worked!
    Car is a 2011 VW Jetta TDI Sportwagon, 6 speed with 47000 miles.....
    Decided after that triumph to replace the stock air filter with a K&N air filter...but ran out of daylight. LOL!icon_rolleyes.gif


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    Jul 14, 2013 4:12 AM GMT
    Sporty_g saidI did it myself today! Went to the Autozone and got a can of ACPRO and followed the instructions...in the video....WOW it was easy and worked!
    Car is a 2011 VW Jetta TDI Sportwagon, 6 speed with 47000 miles.....
    Decided after that triumph to replace the stock air filter with a K&N air filter...but ran out of daylight. LOL!icon_rolleyes.gif


    Well great!

    A relatively new car, so maybe does have a leak. And definitely would take R-134a refrigerant. I presume it's out of warranty, including any extended one.

    So is the cooling improved? Keep on eye on it, a little early to have needed an AC recharge if it doesn't have a leak.
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    Jul 14, 2013 5:01 AM GMT
    ART_DECO said
    shortbutsweet said
    ART_DECO saidI was trained as a Master Auto Mechanic, still sometimes recharge car ACs for friends.

    I'm on my way over with the parts. Are we still friends? icon_wink.gif

    Seriously, though, I'll be performing this service soon. I was under the impression that the minute leaks in the system would be taken care of by additives in the refrigerant. Am I mistaken?

    I recall replacing all the [swaged, the bastards!] power-steering hoses in my car only to find the fluid continued to leak. Only now I couldn't see where it was leaking from. Added some leak stopper, and no more leaks.

    Partly true, IF you use a refrigerant that has optional leak-stop additives. The pure refrigerant itself will not plug leaks.

    And the use of leak-stop in a car AC is controversial. Some contend it reduces the cooling efficiency, for various chemical and mechanical reasons, and may shorten the overall life of the system. In an older car that you don't intend keeping much longer this debate may be a moot point. In a car that's a "keeper" you should try to find & repair the leak without resorting to additives. And that's true for engine coolant systems as well.


    This vehicle is a 1995, so the refrigerant will most likely outlast the car. icon_wink.gif I did purchase one with leak-stop; however, it does not appear to come with an integral gauge. Will I be able to duplicate Sporty_g's success without a gauge? The instructions say to add the "correct" amount of refrigerant -- with no further elaboration -- which seems to be a faintly sinister joke. This doesn't seem to be the sort of thing a talented first-timer can eyeball. Or is it? The air is blowing cool, not cold, and I replaced the condenser and dryer a few years back.

    Thanks to all of you who have provided helpful advice.