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Recharging AC with R134
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06-28-2011, 08:03 AM | #23 |
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I ended up finding a friend who had the gauge set with both high and low and the service port, and checked the pressures again yesterday afternoon. The high side was too high so I purged a little more out of it and I immediately noticed a difference. The fan slowed back down to how it was before and the system is cooling better now. It would appear that by adding the amount I did from the small recharge can it put in too much, which threw the pressures off.
As far as the hoses go, the low side hose and gauge I got is actually a very nice one. I didn't get one of the cheap ones that came with the can, I bought mine separately. But yes, without being able to see both high and low, it was kind of pointless for me. |
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06-28-2011, 09:20 AM | #24 |
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Glad to hear your ac is back. What is your current pressure reading on the low side now?
Before, I wanted to get my low side pressure up to about 45PSI (thinking higher is better). But now I have second thought. Mine is reading 37-38 PSI on the low side.
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06-28-2011, 12:46 PM | #25 |
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Yeah that's what I was shooting for when I got the kit as well, around 45. (Outside temp was around 86) But now it is around the same as yours at idle. Mid to high 30s. I'm just going to leave it alone for now though since it seems to be back to normal.
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06-28-2011, 04:02 PM | #26 | ||
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A quick rule-of-thumb for pressures: Low side: 30 - 35 psi High side: 2x - 2.5x ambient temperature + 100 e.g., at 100F, high side pressure should be around 300 ~ 350 psi. The low side should be around 30 - 35 regardless of ambient temp because it's a function of evaporator temp, which should be near the freezing point of water (in theory anyway). Total refrigerant charge in my 328 is only 590 g, less than 2 12oz cans. If it's only partially low, one bottle of R134a can easily overcharge the system. See the placard under the hood for your own capacity. Quote:
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06-30-2011, 07:07 AM | #27 |
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I don't understand what it is saying. Translation anyone...
what is Charge 1.10 +- 0.03 lbs means. Is that the maximum pressure for this car's AC system? Time to google. So my car takes 1.1 lbs of refrigerant (18 oz). now here is a good video explaining the proper way to service your auto AC. http://www.youtube.com/watch?index=1...31A7BF5C253909
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06-30-2011, 04:12 PM | #28 |
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That's the right way to do it. Problem is if your system is only partially low, you don't know the amount of refrigerant that is still in it so you wouldn't know how much to add. Therefore you use the gauge set to find the proper pressure on both sides. When the pressure is right the amount is about right.
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07-30-2012, 09:21 PM | #29 |
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with a modern BMW, it's really not possible to charge a system by pressure any more. As one knows, pressure varies by temperature and therefore just charging to a pressure (either the low side or high side) just isn't accurate enough. The issue is compounded on the e90: The tolerance band around a full charge (1.1 pounds) is less than an ounce. In my opinion there just isn't enough 'slop' for a DIYer to add refrigerant to the system. Even if one were to start with a system that had been properly evacuated, it's really hard to calculate how much refrigerant is in the system versus left in the can, the manifold gauge and the lines.
I used to think you might be able to charge an automotive air conditioning system like a home A/C unit: determine the required superheat or subcooling, record the appropriate dry and wet bulb temperatures and charge to a calculated pressure based on the refrigerant type. However, since I don't know that the superheat or subcooling is for an automotive air conditioner, I can't follow the same practice. Likewise, because all cars of a given model/year have the same A/C configuration, the system volume is known, one simply needs to charge to a given volume. I don't mean to totally discourage folks from charging their own A/C unit. I've done many cars myself with satisfactory results. My point is to alert folks that the e90 (and probably other BMWs of the same vintage) have relatively low charges of refrigerant and very tight tolerances around what is considered full. This makes overcharging a definite risk. |
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03-22-2013, 09:26 PM | #30 |
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I recharged my ac and I think I overcharged it. I used the full can and the ac blow cold than hot, so I pushed some of the coolant out and it blows cold but the fan is not as fast as before any help.
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03-30-2013, 11:08 PM | #31 |
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I recently purchased a 335 from NY. When I bought it, it was 20 degrees out so I didnt get to test the ac. I noticed it wasn't blowing cold recently. Compressor is kicking on. Low side read 10 psi so I charged it. Weirdly, it barely took any refrigerant to bring it to 35 psi. Air still didn't blow cold, and later on I checked and the pressure had dropped to 30 psi about 5 hours later.
So any ideas? If I have a leak, I thought the air should still blow cold. And why does the pressure rise with just a few seconds of refrigerant? And the compressor is kicking on. |
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03-31-2013, 04:12 PM | #32 |
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As an update, I checked this morning after a 20 minute drive and the pressure was still at 35 psi. So at least no massive leaks. Compressor still kicks on. The weird thing I discovered is that the passenger vents blow colder air than drivers side. Neither one is cold, but the passenger side is colder than ambient. Tomorrow I'm going to get some gauges so I can read high side as well. Im just curious now to see if I can fix this.
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04-01-2013, 09:52 PM | #33 | |
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Dumb question, but I just bought the Harbor Freight gauge set. Is it supposed to come with the proper fittings? Because the ones included don't fit (they're screw on vs. quick connect).
Also, to anyone, how can I confirm the compressor is working? I was going off the fact that when I hit the AC switch, the rpm's rise from 600 at idle to 700. This happened every time and dropped every time AC is switched off. But if the compressor is out, would the rpm's still rise? I wasn't sure if the ECU compensated automatically when the button is hit. Quote:
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04-02-2013, 09:22 PM | #34 |
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Alright, final post about this since I've been talking to myself. But I finally resolved the issue so hopefully it'll be of some use to someone. After getting the gauge swapped out, I was able to get some readings. High side and low side with the car off was 30 psi which was far too low. And then when I turned the car on, the gauges were both at 30 psi which meant the compressor wasn't turning on.
The confusing part was that every time I hit the AC button, the idle would rise indicating the compressor was kicking on and once in a while I was getting a little cold air. As it turns out, the pressure seemed to be just enough for the compressor to start, but then would shut off immediately due to low pressure. So I basically hooked up the refrigerant and pulled the trigger. At first, the pressure started rising immediately like it did before and nothing would happen. Then after about a while of nothing, a long blast of refrigerant finally got the compressor cranked up and as I pumped refrigerant in, the pressure would rise, then immediately drop indicating the refrigerant was moving. After probably 2/3's of an 18 ounce can, the system read 30 psi low side and about 160psi high side (it was 45 degrees out). This is roughly in the correct range and the best part is, the system is blowing ice cold air. |
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06-19-2013, 02:13 PM | #35 |
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Thanks for the follow through. Your post did help me.
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08-29-2013, 12:03 PM | #36 | |
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Got the gauge kit at Harbor freight ($59) and read high/low 75f ambient High= 210psi Low= 29psi Even though I seem to have gone full circle, it seems to cool better now, without obviously overworking the compressor? Still though, I am probably going to go ahead and evacuate the freon, run suction on it for an hour or two and re-service with straight up r134a +PAG oil(stuff I used had fix a leak shit in it). Have everything I need minus the r134a. Suction pump is just this little $15 thing http://www.harborfreight.com/air-vac...ors-96677.html . Just need a really good compressor which my work has. Tag on hood says 1.3lbs +/- .2 Bently says 590grams +/- 10 (20.8oz +/-.4) I guess there is not a gauge that meters out how much is going in by weight Maybe after completely using one 12oz can, I can weigh (using a food scale) an empty can compared to a full can and then expel a little off the full can till it drops enough to get me in range and then fully empty that can into the a/c system. Last edited by Casca; 08-29-2013 at 12:15 PM.. |
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08-29-2013, 02:20 PM | #37 | |
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Your high side is way too high. Either the expansion valve is stuck (stop leak can do this), the condensor is clogged with debris, one of your lines is clogged, or your AC fan isn't working which means the condensor stays hot and pressure stays high. Moisture can cause this too or too much oil. So hopefully it will be fixed once you vacuum the system out.
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09-03-2013, 10:55 PM | #39 |
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It says you need 1.1 pounds of refrigerant plus or minus 0.03 pounds.
So BMW says you want between 1.07 and 1.13 pounds of coolant in your car. Remember that 1 pound is equal to 16 ounces. So converting the recommended pounds to ounces gives you a full charge between 17.2 (16 * 1.07)and 18.08 (16 * 1.13) ounces. (That is actually lower than I'm used to. I've worked on cars that want 3 or 4 pounds). Most r134a is sold in 12 ounce cans. Therefore, you want a TOTAL of no more than 1.5 cans in your system. That's if your system is at a complete vacuum when you start. Do you need to add oil? Most likely not. If you remove your compressor, drain it of oil, and flush the lines, then yes you should add more oil. If you're not doing that (and your compressor doesn't make a grinding noise when it comes on) then you probably shouldn't add oil. Get ready for a long explanation / DIY rant.... How a Air Conditioning works (and how I get my cars to blow 38 to 42 degree air in the summer). Air conditioning is just physics and chemistry and is based on a simple principle: when an liquid evaporates, it absorbs heat (and gets cold). At room temperature and pressure, R134A is a gas. But if you put it under pressure, you raise the boiling point and it becomes a liquid. Suddenly release the pressure and it becomes a gas and becomes cold. So how does a car use this? The AC system is a closed circuit: the refrigerant can't escape. It's just a long tube that makes a loop. In the middle of the system is a compressor. It pressurizes the system (to ~200 - 300 psi) and forces the refrigerant to become a liquid. This makes it very hot, so it runs that hot liquid through a condenser (a small radiator) under the hood. Now this hot liquid travels through a tube until it reaches an expansion valve (also called on orifice tube). This valve lowers the pressure (to about 30 or 40 psi). When it does this, the liquid evaporates, becomes a gas and the temperature drops. This cold gas is blown throw an evaporator that is inside the cabin. The car blows air across this cold evaporator (the opposite of a radiator) to cool the air and then blow that cold air into your face. Now this cold gas flows back into the compressor where it raises the pressure and re-condenses a liquid. If you do not like to do things yourself, or are not mechanically inclined then stop reading. This is a great forum. Read another great article. The following can be VERY dangerous if you do not know what you're doing. Only attempt this if you are comfortable working in a running engine, handling dangerous chemicals, working with high pressure systems, and are not afraid of breaking things or getting hurt. How do you use this knowledge to your advantage. The greater the difference between the low pressure PSI and the high pressure PSI the colder the air will get in the evaporator. Steps to work on your A/C: 1) If you don't know what you're doing, then stop now. This stuff is under pressure and can explode. Pay a professional to do any work you're not comfortable with. I don't want anyone to get hurt. Stop now. I'm just a stranger on the internet. Why would you take my advice when making a mistake could cause bodily harm? DO NOT DO ANYTHING YOU"RE NOT COMFORTABLE WITH. I make no promises and accept no responsibility. Your car, your hand, your eyes... 2) Still here? ok. First you need your system to be completely empty. Go to a shop and have them evacuate all of the refrigerant. Venting R134A into the air is illegal. http://www.epa.gov/ozone/title6/608/faq.html You can be fined. 3) hook a vacuum pump to the low or high side access port. Pull a vacuum on the system. You really want 28 mmhg if you can get it. You want to get every ounce of fluid out. AND under a vacuum the regular moisture will boil out. 4) Let it sit for 12 or 24 hours. This is to check for leaks. 5) If the vacuum held, proceed. If it leaked, then you have to find and fix the leak. 6) Hook a manifold to the high and low access ports. 7) Pull a vacuum again to get the air out of the manifold. 8) Turn on the car. Turn the AC to maximum. The compressor will NOT engage because there is no pressure in the system and the low-pressure cutoff will prevent the compressor from working. This is ok. 9) Place a large box fan or similar in front of the radiator and blow air across the radiator. You want to simulate normal driving and have air flowing over the condenser. 10) Close the high pressure valve on the manifold. DO NOT OPEN IT AGAIN DURING THE ENTIRE PROCESS OR YOU WILL BLOW UP THE CAN OF REFRIGERANT IN YOUR HAND!!!!!!!! 11) Hook up the first can of refrigerant and open the low pressure valve. The can will start to get cold. Both the low and high pressure numbers on the gauge will start to go up. 12) When the pressure gets to around 35 psi you will hear a click and the low pressure will drop and the high pressure will climb. Then it will click again and the numbers will go back to 35psi. What happened? You had enough pressure that the low-pressure sensor was activated and the compressor kicked in. That's good. 13) As you add more refrigerant, the compressor should kick on more often and for longer durations. This is the compressor cycling. Eventually it should come on and stay on. 14) At some point, you'll notice the can of refrigerant is very light and the numbers on the gauge aren't moving any more. The can is empty. DO NOT UNHOOK IT YET. 15) Get a bucket of HOT water. As hot as you can get (without burning yourself when you stick your hand in it). 16) Place the can of refrigerant in the bucket of water. What are we doing? We're increasing the pressure in the can and forcing the coolant into the AC system. The can should feel cold at first, and then get warm as it absorbs the heat from the water. 17) When the can is the same temperature as the water, close the valve on the can. 18) Close the low-pressure valve on the manifold. 19) Remove the can from the valve and attach a new can. 20) Open the valve on the can. Open the LOW-PRESSURE valve on the manifold. 21) Have an assistant rev the car to ~1900 RPM and hold it there. This is to simulate cruising speed. It will speed up the compressor and pull more coolant into the system. 22) How do you know when you're done? Good question. There's no good way to measure how much refrigerant you've let out of the can. You can try to weigh the can and stop when it weighs 6 ounces, but that will be hard with the charging hose attached. If you think you can do that, then that's great. Go for it. When you have about 1/2 a can left stop. If you can't do that, then see below. 23) Shut off the low pressure valve on the manifold. Close the valve on the can. 24) Shut off the car. 25) Remove the manifold from the low and high pressure ports. 26) DO NOT REMOVE THE CAN FROM THE VALVE. You still have 1/2 a can of refrigerant in the can. Remove the valve and it will empty. The valve is also a seal. Put the can in your garage and save it for another time. If you can't measure how much is left in the can, then how do you know when you're done? When the compressor stops cycling and stays on, you should see that the high pressure value continues to go up as more refrigerant is sucked in, but the low pressure remains fairly flat. As long as the low side remains fairly flat but the high pressure goes up, then you're ok. We want as great of a difference between the low side and the high side. When you see the low-pressure side start to go up and the high side stays the same, STOP YOU"RE OVER CHARGING THE SYSTEM!!!!! If you do this right (and it can take a few tries before you get the feel of when to stop) you can get air coming out of the vents that is between 38 and 42 degrees F. Good luck and don't hurt yourself!!! Last edited by minifridge1138; 09-03-2013 at 11:09 PM.. |
09-08-2013, 11:29 PM | #40 |
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FWIW, I just did a recharge on my '06 330. I used the information in this thread, so thank you all for posting what you did. The A/C was very "not cold" when ambient temp was in the 90s, really not even "cool" air, more like about 10 degrees cooler than ambient, and passenger side was a little bit cooler than driver side.
I bought the Harbor Freight gauge set. First, the PSI numbers: Before the recharge: High Side: 190psi Low Side: 25psi After the recharge: High Side: 226psi Low Side: 35psi I used about 9oz from an 18oz Arctic Freeze can from Autozone. problems: The gauge set does not come with an r134a connection for the supply line (the yellow middle port on the gauge manifold), so there's no way to connect the Autozone canister to the manifold supply line. There's a way to "build" a connection by buying an R12-to-R134a conversion kit, which has an r134a connector in it, and then buying the proper threaded adapters to go from that r12-to-r134a connector into the yellow supply line to the manifold. I got tired of driving around looking for the parts so I decided just to use the manifold to measure the high-side pressure and then just use the gauge that comes on the arctic freeze recharge bottle to measure the low side. Not ideal I know, but that's what I did. After I was done, the A/C is definitely much colder, the compressor is not exhibiting any issues like cutting-off due to too much pressure, and overall so far so good. Ideally would have liked to do the vacuum thing...maybe next summer. Ironic part of my day: while driving around in my truck collecting the stuff to do the recharge....the A/C went out! Unbelievable! |
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09-10-2013, 11:53 AM | #41 |
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Just take it somewhere for 115 bucks. Not worth messing with it.
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08-25-2014, 09:14 AM | #42 |
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I know this thread is old. But I just used it to vacuum my system and recharge since it wasn't working well. Thanks for posting up how to do it. I got my system to start blowing about 40 degrees less than outside temp. Sometimes you gotta love harbor freight tools.
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05-18-2015, 08:50 PM | #43 |
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Great thread!! It was very helpful for me. My '07 335I, which my mom drives, was blowing hot air the other day. Bought a kit called AC Pro, with the gauge. The gauge read 0. Tried pumping 134A in, but it blew straight out of somewhere in the engine bay. Went to midas, and got a blown AC condenser diagnosis. Brand new oem costs $630! Behr makes one new, for $250, but couldn't confirm fitment, so I went with a low mileage oem off ebay. Installed today, and pumped in the gas using the instructions on this page. Voila! ICE cold AC!! Thanks to OP, and good luck to all who try this very easy DIY.
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05-26-2015, 12:38 PM | #44 |
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Did you have to add PAG oil back in? I'm curious.....
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