How To 'Top Off' Your AC System 

You and me both! I appreciate that he made a detailed video about what to do. Seems like most videos out there are either "hey here is how you add freon with this can from the auto parts store with a gauge already on it!" ... or ... "A/C work is super complex and only trained professionals should ever perform any work on an A/C system."

quick question when using the manifold gauges and you are ready to recharge refrigerant does the high side pressure needs to be open or closed?

@@artgonzalez9706 I keep my High Side pressure knob Closed

What should the running pressures be on the R134a refrigerant in a vehicle? Vapor line 40 psi and Liquid line 200 to 220 psi? I read that the static pressure should be 90 to 100 psi.

​@@coolramoneyou can google r134 gauge readings or something like that and there is low side and high side ranges given multiple outdoor temperatures.

O

next level mama, next level

Hi Trevor, I have no experience with car AC systems but, can you tell me why nobody push the air out of the blue line before filling the system? Thanks!

@@MsLincos You should. Very important. I'm guessing Eric forgot to mention/show that. I'm sure he knows.

A message for all of the "ASE certified master techs" watching a video about how to top off refrigerant, the orientation of the bottle is completely irrelevant. The state of the refrigerant is determined by a few things first pressure second temperature. If you think the orientation of the bottle changes the state of the refrigerant from gas to liquid you have a fundamental misunderstanding of how substances change state and you should avoid telling actual professionals how to do their job because you've made yourself look like a moron in the process. Also consider that the hoses travel UP AND THEN DOWN, this still doesn't matter at all in reality but even in the scope of your ignorant view would still debunk what you're saying. "I copy pasted this so it's not really directed at you but it confirms what you're saying about the orientation of the bottle being irrelevant"

The orientation of the bottle is CRITICAL unless it is 100% full of liquid. As liquid is removed then its level goes down and above it you have a combination of gas and a vacuum, which is not what you want to pull into your system. Liquids are always heavier than their gas counterpart and gravity always sucks. The reason the height of the bottle doesn't matter is because the system pulls the liquid freon from its container (or freon gas, in your case). The same thing is true with filling a lighter with Butane. To get the butane liquid to flow you have to turn the bottle upside down. Propane is different because you actually want to pull out only the gas and not the liquid.

@@kylekoster3432 The orientation of the bottle is CRITICAL unless it is 100% full of liquid. As liquid is removed then its level goes down and above it you have a combination of gas and a vacuum, which is not what you want to pull into your system. Liquids are always heavier than their gas counterpart and gravity always sucks. The reason the height of the bottle doesn't matter is because the system pulls the liquid freon from its container (or freon gas, in your case). The same thing is true with filling a lighter with Butane. To get the butane liquid to flow you have to turn the bottle upside down. Propane is different because you actually want to pull out only the gas and not the liquid.

Does that mean you basically connect the low and high sides to the vehicle and then at the gauge ends of the low and high, you open the valves to let some pressure push the air out and then close the valves? Or are you meaning purge somehow from the charging ends of the hoses where refrigerant is added, allowing it to escape the vehicle side before fully seating the low and high sides to the connection ports? Thanks

@@Roboticdoughbull3k After hooking hoses to car, I crack open the low and high side hose at the a/c gauge manifold to purge a small amount of gas which pushes out air in hose.

@@JT-qf4it I gotcha now, I figured but just wanted to check. I got a set last year and am about to start helping out the family vehicle fleet, little things like that are good to know. Much appreciated, thank you!

I'd connect the high side the purge from high to charge hose. Then hook up charge hose or put back on holder. Then purge high to low. Then hook up low side. Then you're purging possible contaminants and air from the manifold itself.

In addition to the purging, I usually hook up the high side hose to the car before turning on the AC so it's not under high pressure, and hook up the low side with it running, so the valve is at the lowest pressure. After it's all done and when disconnecting the hoses, remove the low side first while the compressor is running, and remove the high side last after shutting down the car, and allowing the pressure to equalize and drop back down. That helps reduce the bit of refrigerant loss from opening the connections under pressure.

Good to know about the Sealant Leak damage potential. As far as leak test, a vacuum is never the way to test for leaks, only nitrogen positive pressure. 134a is available to anyone here off the shelf at most stores in small quantities.

R134a is (still) legal for sale to anyone in small quantities per federal guidelines, but states can be more restrictive, although the EPA is trying hard to change that. On the premise that they will eventually do so, getting an EPA 609 certification is pretty easy, and can be done with an online (open book) test for $20-$25. I'd like to know more about the sealant leak detector, I've never heard of such, and I'm currently (casually) shopping for my first recovery machine, so it would be helpful to know what to look for, as I'd hate to have it ruined by someone else's gunk!

F I’ll i ut

Js

If you're charging slowly enough and in small quantities at a time, the liquid will have time to boil into gas before it can adversely impact your compressor because well, the pressure is low enough to boil it. If you're starting from scratch (and the engine is off), you can also charge liquid on the low side (use a scale to know how much you're putting in!), but that tends to work best on fixed orifice tube systems, not on TXVs, because a fixed orifice tube system will tend to equalize much better when the compressor is off. Either way, check the specs for the system and don't overcharge it. I've also graduated to a 4-hose manifold with valves on all of them, so that I don't have to disconnect the tank to pull a vacuum, and I wish I'd done it a long time ago...

I don't typically listen to Kilmer, but I always add refrigerant by weight and add as a gas, not a liquid.

Everyone is belaboring this point, but it can be summed up like this: It can be done either way, but unless you think you know exactly the pros and cons, always charge with the can right side up, charging with a gas. Never charge with the can upside down, trying to charge with a liquid.The only reason to charge upside down is to make faster work of it, and if you're just trying to get the job done on your own car you don't mind taking a few extra minutes. If you see your A/C guy charging upside down, he's reckless. Move on to another guy.

Agree with all you stated but wish to add a bit more. You can not compress a liquid, this is the basics of hydraulics. So why send a liquid in to an air compressor. Chances ate increased of causing premature failure of your compressor. It may work, as Erik has demonstrated. But its not how the compressor ordinarily works. Check out any air conditioning theory of operation. Gas is compressed into a gas. Both sides are gas. High side obviously more pressure than the low side but no liquid near the compressor ever, until beyond the centers of the evaporator or condenser heat exchangers . I am amazed this hasn't caused more troubles for you Erik.

@@deanstuder1775 maybe because he just add tiny amounts quickly?

This is a good point. I heard that before. I was surprised 😮 too.🤜🤛

I have no pressure when I connect my gauges. That means I have a break in the system?

Chris that’s means your system is empty

Depending on the type of AC system you have, these cans with the built in gauge are worthless.. you can get them to work ok on a fixed oriface tube system.. but a newer system with a TX valve that gauge wont be accurate as the TX Valve throttles the refrigerant on the low side depending on the amount of superheat on the vapor line going to the compressor.. It is very easy to overcharge a TXV system with these can setups since the pressure doesn't change much if at all on the low side. These systems are monitored on the high pressure side when charging.

Borrowed mine from O'reilly.

If you DO have too much refrigerant in your system, how do get rid of it?

@@colebennett6424 the official way is to use a recovery machine to remove the refrigerant. The diy way is to release it to the atmosphere. Just make sure you're monitoring the pressure so you don't go overboard and have to add back again afterwards. 😭

Questions.. I changed my compressor, expansion valve, all O-rings, flushed my system and refilled my system with the correct amounts of oil and R134a. There were no leaks, all seems well with 2 exceptions. It takes a few minutes before it starts cooling and once it cools it seems like it isn't cold enough. I made sure the exact amount of R134a & Oil went back in the system. 1) Should I add a little more R134a? 2) Would the new expansion valve cause it to delay cooling maybe due to it opening slowly or something?

Also, the 2-3 minute delay only happens after the car has been off overnight. If I am out using the car during the day, let it sit for an hour or two and then start it again, the cooling happens right away as normal..

@@Conald_isAfalseProphet Year, make, model, engine size of vehicle? Orifice tube or expansion block, or metered line? When you say cooling...what is the duct temp in center vent, max cool and recirculate. What were your final high and low side readings on the manifold guages...and what was the ambient temperature...ie temp in the shade. When you finished the repairs and added the oil, did you evacuate the system...minimum of at least one hour?

​@@majwor3763 Thanks for the response. - 2010 Nissan Altima 2.5 SL - I made all repairs, flushed, changed drier, closed the system, evacuated for an hour, it held at negative 27 for 12 hours. I then bled the yellow line before opening the low side to begin adding freeon. - Expansion block / valve. - Didn't check the vent temp, will have to check later, but it was obviously not as cool as it should be. - Low side was at 36 PSI, High side was 145 PSI. - Temp was 80 Degrees Fahrenheit and the humidity was 80% as I'm in south Florida. -System called for 0.55 + .025 kg which translates to 575 grams from my calculations. I added exactly that. 1 thing to add.. the 3 minute delay only happens after the car has been off overnight. If I am out using the car during the day, let it sit for an hour or two and then start it again, the cooling happens right away as normal..

@@Conald_isAfalseProphet When you say 27"hg...was that the best that your pump could pull a vacuum or did it leak down to that from 30"hg...most good pumps can pull 29.5 - 30". You want it to pull as high a vacuum so any moisture is able to boil off. Its important to know what the center duct temperature actually is. Go to a grocery store and get a meat thermometer. You would want it around 40-45 degrees F. Low side pressure is good...High side is low...should be around 180-200 degrees F. Both cooling fans {if it has 2) should be running when the compressor is on. According to what you are saying...your system holds approx. 22ounces which is about 2 cans is the US. I am wondering if either there is some kind of restriction...or the charge is still too low. Take your guages and rehook them and see what the static charge is and if they are the same pressure on the low and high side.(A/C NOT engaged) Should be around at least 90psi but more like 125psi. After that crank the engine and turn on the A/C...max blower and recirculate. Use you hands afeel the A/C lines. THe low side lines should be really cold to the touch and even sweating. Put your hand on the condensor (looks like a radiator...located in front of the radiator) feel from one side to the other...it should be hot to the touch all the way acroos and up and down after the system has been running for about 15 min. If its just warm then there is and issue. Anthing after the compressor on the high side should be VERY warm and or hot to the touch till it pass through the expansion valve. once it goes through the evaporator...any low side line should be really cool/cold to the touch. I would try to add one more can...slowly to get the high side pressure up. As you are doing that take your garden hose (with a nozzle) spray across the condensor all the way across side to side...and up and down. The fans will spray water every where...dont worry about it. This will change your guage readings and fool the expansion valve. The compressor may cycle off and the high side readings will come down. Once the condensor dries out the compressor should kick back on...the low side readings will drop and the high side should start to rise. This is a way to get sluggish system working thats being a pain. May have to do this a few times. The high needs to get to around 200 psi, while the low side stays around 35-45 psi. Also see if holding the throttle down around 1800-2000 rpms gets that high side up! These are some things you can try. Hope this heps.

Is that basically on ALL car AC systems, or are some higher, or lower??

@@tscrain8277 all.

If that's a good rule of thumb, then why do they have charts?

@@Matthias53787 charts are the right way to do it. A rule of thumb is just a rough idea. Example: on a customers AC i am looking for around 70 psi low side on an r-22 system. Thats a rule of thumb. But it can be higher or lower depending on other factors. It gives me a starting point

This seems super useful. (Not being sarcastic)

I always go with idle as a base. They should correlate with rpm. If you’re at 30 psi low side and 170 high at idle you’re fine. There are other factors such as ambient temperature to factor in

Idle… ambient temperature and humidity are factors that will affect the pressure readings.

I agree on this, I’m going to do this next time

I remember those 5 cylinder.

It's also illegal to "top off" the AC system to fix the problem, it needs to be evacuated and the leak must be fixed before it's refilled with 134A. This is why every one here cringes when their AC stops working because you're guaranteed to spend hundreds just to fix it. And those refrigerant substitutes may even make the problem worse by contaminating your whole A/C system or damage the compressor.

Any body know the different between 134 R refrigerant from Walmart, about $5.00 a can and other more specific from the auto parts, do they work the same ?

the $5 cans are the ones you want. they are pure HFC-134a and do not have the oil and additives in it. In the case of AC, cheaper cans are the better ones.

Chaddz3 got it right. And, oh yeah, it's only $5.

www Sax

if you opened up the airconditioning system then you need to evacuate it under vacume before recharging

@@PeterShaw-lb9lt right, if i opened it up. But i can just hook up to the lines and add if it hasnt been tampered with

I am not ⅞The