Engine Size: 2.3
Refrigerant Type: R134a
Ambient Temp: 85
Pressure Low: 38
Pressure High: 225
Country of Origin: United States
I attempted to vacuum and recharge my system after reading the guide on this forum. I was wondering if I should use the high/low readings with my AC set to MAX AC or with it turned to Vent with MAX Fan Speed?
With my car set to MAX AC my Low is 38 and my High is 225 at an ambient temp of 85 degrees while the the ac is blowing out of the vent at 52 degrees. When I set my car's AC to Vent with the fan speed on MAX my Low is 52 and my High is 248 with the same ambient temp of 85 degrees while the ac blowing out of the vent is 65 degrees. All of this is while the car is in the driveway idling.
Which reading should I use and why? Why do the pressure readings drop when I switch from vent to max ac?
and what can you interpret from these readings? Is my system too low? or overcharged?
My refrigerant cans came with a guide showing that at 85 degrees my low should be 45-55 psi and my high should be 225-250 psi. My car takes 21 oz of refrigerant and I honestly think that I put in more than 21 oz. After charging with two 12 oz cans my gauges still read much lower then the those numbers from the guide so I decided to hook up another can and see if I could get it closer to those numbers. I really don't know how much refrigerant I have in my system but when I got my number up to where they are now.. as i have described earlier in this post.. i decided to stop and get some opinions and advice...
Thank You for any help or advice you can give a noob!
Edited: Mon July 05, 2010 at 11:12 PM by Strs90
Vent passes raw hot/humid outside air through the evaporator, max A/C recirculates air from inside the car so there is less cooling demand. Do the stress test at 1500 rpm on vent, high fan, and the car doors open so it doesn't cool off at all inside. Recharge after evacuating should be done by weight to the specified amount so you'll know it is properly charged.
Edited: Mon July 05, 2010 at 11:11 PM by mk378
Ok I will do the stress test tomorrow and post it here..
This may sound really dumb but I will ask anyway.. If I set the cans on a postal scale and watch for them to change in weight(oz) would that be an accurate indication of how much refrigerant I have charged the system with?
Edited: Tue July 06, 2010 at 12:17 AM by Strs90
Hi, i agree with your problem.We are generally not aware of the technical things.
Better consult an expert to avoid any risk.
Good Luck !
Definitely not undercharged. Two whole cans is more than enough, the third was a mistake. Unless there's a major mishap and you leaked a lot out by mistake, expect to leave about 1/2 oz behind in each "empty" can. Test at higher rpm will show if maybe the compressor is getting weak.
Thank you for the responses!
I ran the stress test this morning at 80 degrees ambient temp with the car set to 'vent' with fan speed on high and throttle at 1500 rpm. My low was 35 and my high was 250. The temp of the air coming out of the vent was 60 degrees. How would you interpret these numbers?
When i look at the pressure guide that came with my refrigerant I would assume my low is too low and my high is too high. It says when this is the case that there is a "possible blockage of the expansion valve or orifice tube." I researched what an orifice tube or expansion valve is and it seem pretty straight forward and not expensive at all. Would you recommend an orifice tube repair kit or just replace the expansion valve?
BTW would a postal scale work relatively the same as a charging scale? I am thinking of having the system recovered and starting again using a postal scale that measures ounces.
Thanks again for any help or advice.
Edited: Tue July 06, 2010 at 11:16 AM by Strs90
Also, I read on another post that auto manufacturers set the refrigerant capacity based on all climate conditions. If this is true (given that I live in a climate that has hot weather year round) would if be better for me to be a 1/2 oz short of 1/2 oz over the listed recommended capacity?
Some serious advice to help prevent possible compressor failure issues that can result from too little or too much refrigerant....stop this playing with the system and have the system serviced by a knowledgeable technician that will utilize the correct equipment.
My spec book indicates a charge of 1.30 lbs. (21 oz ). This charge rate should be within 5-10% of standard charge to maintain proper lubricant flow. The over charge side which may result in excessive pressure could result in possible clutch overheating problems. The only true method to insure proper charge is to use the proper equipment. Cans and pressures are not an acceptable method to accomplish this very important step of AC repair.
The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Not really looking for politically correct advice. I enjoy "playing with the system" and don't really care if I burn up a compressor. I found what I was looking for elsewhere though. Thanks anyway guys.
Really doesn't make any difference if you are in MAX AC or not if you properly charged your vehicle via pressures following the basic rule. Doors open, engine at 1,500-2000 rpm, AC on, blower at max. With an initial charge, have to be darn careful not to introduce air into the system, almost impossible to do if changing hoses from vacuum to charge.
Really can't comment on your posted pressures, you did not specify ALL the conditions these pressures were taken at, and yes, they do very all over the place.
Thank You for the reply NickD. With the initial charge, after i reconnect the hose from the vacuum to the refrigerant, I crack the hose open a little where it connects at the gauges and let air out till i smell refrigerant. Is there anything else I can do to ensure as little air gets into the system?
And what other conditions are needed?
I had my system recovered today. I have the vacuum on my car right now and am going to recharge using a scale in a little while. I will post all the conditions you can give me if you let me know what else there is.
After having the refrigerant recovered earlier today I vacuumed it for a little over an hour and the gauge was reading about -28. I shut off the manifold gauges and let it sit for 10 minutes and it kept the same vacuum number. So I recharged the system with the help of a friend using a charging scale. I put exactly 21 oz of refrigerant in the system.
I am concerned though. The first 12 oz can went in fairly fast. The second can started off okay but then stopped about 6 ounces short of 21oz. I tried shaking the can like the directions showed but it still didn't change in weight. The only way I could get the last 6 oz into the system was by dipping the can in warm water like like I saw in a youtube video.
Is it normal for refrigerant to be so stubborn like that? As it was happening I was concerned it was happening because somehow I was overcharging the system. Is there anyway after vacuuming a system that somehow it could still have refrigerant in it?
Also, I checked the gauges and both the high and low seemed a little high to me.
Let me know what all information is needed to evaluate the system and I will run a test and post back.
Two way (two valves) were intended more for diagnosing an AC system, the problem is, you have to move the yellow hose to switch from vacuum to charging, also either the red or blue hose to purge out the lines with some unknown amount of refrigerant. There is no way to maintain a high vacuum when you have to change hoses, system has negative pressure and air will get in.
Would be nice to have a charging station, were hoses are connected only once and the station lets you switch between vacuum and charging without removing hoses. Next best thing s a four way manifold gauge, where you have those extra valves to switch over. Here you draw a vacuum clear up to the refrigerant closed valve, pull a vacuum from all the lines, close off the vacuum source and switch to the charging source. In the FAQ section, can find other means to work around this.
AC systems are not designed for vacuum, that negative pressure pulls the ports open and the lip in on compressor seals, so have to switch from vacuuming to charging in the shortest period of time.
Air in the system not only causes weird pressure readings, very high with poor cooling, and also forms acid that will eat the inside of your system.
Ah I see NickD. I haven't researched the cost of that type of equipment but I doubt I would use it enough to justify the cost. It would be fun to have though.
When you say "so have to switch from vacuuming to charging in the shortest period of time." It seems like the system will vacuum in only a matter of minutes... but everywhere I read it says to vacuum for at least 30 minutes or an hour.. Is this a bad thing to do.. would I be better to vacuum until I reach the desired vacuum and then stop?
I only have a vacuum pump and manifold gauges so far. My next door neighbor owns his own residential HVAC repair business. So I got him to help me the last time I charged the system and we used one of his charging scales. To me it seemed like a normal scale.. only it did math for us.
From iceman: "How much refrigerant of your charge rate of 21 oz was allocated to pre-fill your hose/manifold assembly? " -- We 'zeroed' out the scale after bleeding out the air in the manifold hose.
I have recharged my system twice. The first time I used IDQ's Artic Freeze Ultra Synthetic and this time I used Dupont Suva 134a. I have read on different forums that anything with leak sealer is bad news.. so I decided to try the Dupont the second time. I haven't had time to check the temps at the same ambient temp yet.. But I am fairly sure my car is at least 5 degrees warmer with the Dupont refrigerant over the Arctic Freeze. Does that sound normal? Is there a preferred type or brand of refrigerant?
I know based on my earlier posts it sounds like I overcharged my system. Honestly I am doubtful that I did so as severely as you probably think though. I should have specified but the first time I charged the system I was having a hard time getting the second can of refrigerant to empty. So I purchased another can and "tap" and had the same problem with that can. I wasn't sure how much was still left in the cans until I had the scale to weight them. I weighed the other two cans and I only used approximately a little more than half the first can and about a .25 of the second can. So all together something like 12 oz + 7 oz + 3 oz = 22 oz............ My point of this rambling.. Is it normal for cans to stop emptying or the system to not want to charge? For instance the second time I charged the system.. I was about 6 oz short of my goal of 21 oz.. and the system stopped charging and the scale had the same reading for at least ten minutes. It wasn't until I would dip the can in warm water that I got it to finally charge all the way.
I think I am going to leave the system as is for now and see how it goes.. but I am fairly confident it is charged to the correct amount now. I actually work in an auto repair shop but we don't do AC work. Several of the technicians have worked in shops that did though so I have been getting advice from them also. I can get parts really cheap through the shop so I am not too worried if it breaks. It probably needs some of the parts replaced anyways. Plus if I really need to I can get one of the techs with AC experience to help me.
Also, I hope my "asinine statement" wasn't offensive. I just like tinkering around and will probably replace the compressor anyway. I just purchased the car used and so far I have replaced the struts, coolant, transmission fluid and screen, brake fluid, power steering fluid, spark plugs, belt and tensioner, brake pads, and changed out the grease in the cv axles.... I ran out of things to do.. and I wasn't and still am not happy with the performance of the cars AC.... If I break it and can't fix it then I might take it to a shop.. but for me this is a fun way to learn about the AC system.
Just thought of something else.. i could ask questions forever i think.. Why do the DIY cans of refrigerant with the built in gauge not cause more problems?
Edited: Fri July 09, 2010 at 1:50 AM by Strs90
Didn't say anything about how long to run a vacuum, I personally prefer about three hours, but stated switching from vacuum to charging, like the the instant you valve off the pump, valve in the charge.
Recommended refrigerant weights are mean values, with skill, knowledge, experience, ability to read both PT and RH charts, can custom charge a system as all have production tolerances, and your equipment has to be accurate.
We've updated our forums!
Click here to visit the new forum
Copyright © 2016 Arizona Mobile Air Inc.