Proper method of charging air conditioning system

[monteperformanc]

Now that I think I have my leak issue solved, I am going to recharge probably this weekend. The last time I did it, I followed the article on gnttype.org and I had some problems. What is the proper method for our cars? Is it to initially fill through the low side port, or high side port? Liquid or gas? How much? Then after you start the car and run the a/c, I know to charge through only the low side port, but do I do it via liquid or gas? Thanks.

 

[TurboSpeed]

Do it vapor, and every now and then tilt the can for a second or two for some gas, but not to long or you can damage the valves in the compressor. Sometimes you have to bypass the low pres. switch to keep the compressor on while you fill and onyl while you fill.

 

[hesermon]

Turbospeed is correct! I would add that it is very important to vacuum the system down to 30 inches of vacuum for about 20 minutes. Then let is sit for about 10 to 15 minutes under vacuum to make SURE that your leak is fixed. Hook to the low side, start the car and turn the ac on max/high. As speed said, short the compressor by using a paperclip in the pressure switch. Take your time, if you're using can-granades it should hold 3 full cans but will take about 20 minutes to charge properly, tilting to about 3 o'clock every few seconds.

 

[monteperformanc]

Okay then so i should not be filling any while the car is off? I should turn on compressor with the system completely vacuumed down? I didn't know if that was bad. Also forgot to mention I am using a 30 lb tank, not the small cans if that makes a difference. Thanks.

 

[hesermon]

The only difference that the 30# makes is that it is very easy to over charge and damage the compressor. I have to assume that you have gauges if you have a tank. Your system should hold about 48 oz. of r134a (54 oz R12 - 10%) along with 9 ounces of PAG 100 oil. Just watch your gauges and do not let either go into the red. Take your time and slowly add until the low side shows 40psi and the high side is between 225 and 250 psi while the compressor is running. Remember that your low side will increase with the compressor off as the system equalizes. I can't stress enough how important the vacuum is to get the right pressures without overcharging. BTW, if you haven't done it, now is a good time to switch to the red orifice tube. It will drop you temp at the vent by about 8-10 degrees.

 

[Rich Gio]

X2 on the vacuum! I let it run overnight and was able to get it down to 300 microns. (If I remember correctly). Also, if you are having a hard time getting the last can to pull in, put it in a bucket of warm (100 ish) water. That'll keep pressure up in the can and it'll shoot right in. WEIGH IN YOUR CHARGE , TOO!

 

[87 WE2]

The only difference that the 30# makes is that it is very easy to over charge and damage the compressor. I have to assume that you have gauges if you have a tank. Your system should hold about 48 oz. of r134a (54 oz R12 - 10%) along with 9 ounces of PAG 100 oil. Just watch your gauges and do not let either go into the red. Take your time and slowly add until the low side shows 40psi and the high side is between 225 and 250 psi while the compressor is running. Remember that your low side will increase with the compressor off as the system equalizes. I can't stress enough how important the vacuum is to get the right pressures without overcharging. BTW, if you haven't done it, now is a good time to switch to the red orifice tube. It will drop you temp at the vent by about 8-10 degrees.

About the red tube orifice, do you have a part # or info on what vehicle it is from?

 

[driveshaft man]

I'm sure there is a reason that this is not recommended...so chime in !
I usually shoot liquid into a vacuumed system,engine off, from a drum until it equalizes.Wait 10 min or more until liquid has time to boil off into gas then start and check pressures....usually a little to top it off after system stabilizes and its done.

 

[charlief1]

The red orifice tube is out of a mid 90's Ford pickup. Engine ect doesn't matter.

The best way to charge the system is to suck it down for at least an hour with both valves open. Once it's down to 30 inches of vacuum close the valves for 15-20 minutes and check to see if it's lost any vacuum. Turn suction pump on again and let it sit for the rest of the hour at least. Longer is prefered if you can do it. Once you're satisfied and it's holding good close both valves and hook up tank. Purge the yellow hose by loosening it a few times. It has a sealing system built in but will spurt some. YOu will need the tank sitting on the valve side to do this. Leave it this way through the charging.

Once you're satisfied that the line is purged open both valves slowly and charge liquid. yes liquid. The system will equalize the pressures and when it's done close both valves. Wait for a few minutes and start the car. Turn the AC on to max with the windows open and the fan on high. the compressor will cycle on and off at first. Slowly open the low side valve but not all the way. The tank is still sitting on the valve side and it's not a problem, believe me. Get the low side pressure up to around 40-45 PSI and check the high side pressures.

When you crack the valve it acts like an orifice or expansion valve and the liquid will flash to a vapor so don't worry about it, and yes, I'm a ASE Master Tech and do this for a living.

 

[monteperformanc]

Thank you. One thing I'm not sure if it was mentioned but I am using R12. I know the pressures are different vs. R134a.

 

[charlief1]

Low side for both are about the same but the high side will be lower than what was posted above. When you get it done post the pressures and I'll be more than happy to help you if you need it.

 

[monteperformanc]

After I replaced the busted o-ring I vacuumed down (monday night) for 45 min, and then left the gauge hooked up. It loses about 1 psi per day. So it seems I still have a leak somewhere. This is really getting on my nerves.

 

[charlief1]

Do the low side as a R-134 fitting and shoot it up with some dye and refridgerent. This should help you find the leak. Once you've found it then pull the conversion fitting off and go back with R-12. Cheapest way I can think of to do it.

 

[Rich Gio]

I'd vacuum it for longer than 45 minutes. I was still hearing moisture boiling off after an hour. Let it go for a few hours. If you have a micron gauge, use it. Much more accurate than a Vac gauge in a deep vacuum. Mine still leaked about 1 psi per day as well. I used Red angel leak stop with UV dye and it's been holding rock solid for 4 months.

 

[monteperformanc]

Do the low side as a R-134 fitting and shoot it up with some dye and refridgerent. This should help you find the leak. Once you've found it then pull the conversion fitting off and go back with R-12. Cheapest way I can think of to do it.

I had made another post earlier about my leak. http://www.turbobuick.com/forums/general-turbo-buick-tech/322259-trouble-finding-c-leak.html

I thought I had it fixed when I found a broken o-ring. The only place I saw the dye was by this fitting. Apparently it's still leaking somewhere else. This is getting really frustrating because I keep spending money on tools and parts for this, and I get nowhere. By the time I figure it out, it will be winter! I guess the next thing is opening up the airbox and checking out the evaporator.

I'd vacuum it for longer than 45 minutes. I was still hearing moisture boiling off after an hour. Let it go for a few hours. If you have a micron gauge, use it. Much more accurate than a Vac gauge in a deep vacuum. Mine still leaked about 1 psi per day as well. I used Red angel leak stop with UV dye and it's been holding rock solid for 4 months.

Don't have a micron gauge or know what that is?

 

[Rich Gio]

I had made another post earlier about my leak. http://www.turbobuick.com/forums/general-turbo-buick-tech/322259-trouble-finding-c-leak.html

I thought I had it fixed when I found a broken o-ring. The only place I saw the dye was by this fitting. Apparently it's still leaking somewhere else. This is getting really frustrating because I keep spending money on tools and parts for this, and I get nowhere. By the time I figure it out, it will be winter! I guess the next thing is opening up the airbox and checking out the evaporator.



Don't have a micron gauge or know what that is?

Pulling a good vacuum before charging a new system with refrigerant or after a repair is essential for the proper operation of an air conditioning system. Proper operation, its longevity, and the time you spend at the jobsite all relate to dollars in your pocket. In addition to the vacuum pump, a micron gauge is an essential tool. Below is a description of how the gauge works and why it is used in the HVAC industry.


Preventing Problems


A typical micron gauge.

A micron gauge measures the amount of air or “noncondensables” and moisture in a system. The unit of measurement used is a “micron.” The gauge is placed between the vacuum pump and the middle port of your manifold set. The lower the micron reading, the deeper the vacuum. The deeper the vacuum, the lower the amount of air and moisture in any given system. Why is this tool necessary? It can help you prevent problems like the following.


Potential Problem #1

If moisture is left in the system, some of it will turn to ice when refrigerant is introduced into the system. If enough moisture is left, larger ice particles will form and can block the cap tube or piston, causing a restriction in the metering device.


Potential Problem #2

If moisture and air are left in the system, they can form acids when combined with chlorine (which comes from CFC or HCFC refrigerants such as R-12 and R-22) and oils (from the compressor). Over time, these acids eat away at the compressor’s motor windings and cause premature compressor failure.


Potential Problem #3

If moisture and air are left in the system, they can cause higher than normal head pressures. These pressures can mislead a technician and cause higher discharge valve temperatures, which again can cause premature compressor failure.


Potential Problem #4

If a micron gauge is not used, a small leak will never be detected using conventional gauges. Conventional gauges use inches of mercury (Hg) to measure vacuum. Most gauges go down to 30 inches of Hg. If one inch of Hg (at 32 degrees F) is approximately equal to 25,400 microns of Hg (at 32 degrees F), you can see how much more accurate using the micron gauge tool can be. It is recommended pulling new systems down to 400 microns or even less if time allows. If a leak is left in the system, first you will experience indoor coil freeze-up, then no cooling and/or compressor damage.

 

[monteperformanc]

Thank you Rich. Just looking up the Red Angel product as well. Did you use the aerosol-type can, or the bottle along with the separate injector adapter?

 

[Rich Gio]

Thank you Rich. Just looking up the Red Angel product as well. Did you use the aerosol-type can, or the bottle along with the separate injector adapter?

I used the Oil injector. If you were closer, I'd loan it to ya. Mastercool make a nice one. Thing I like about red Angel is it's not supposed to clog up the recovery equipment if you ever have to pump your system down again. I know it's not the "right way" to fix a leak , but I spent hours trying to find that tiny leak with no luck. I think my leak is thru a porous spot in the hoses. I don't see any dye!

 

[charlief1]

I've considered red Angel it before and my old boss tried it, but didn't follow the directions. He only used 1/2 of the bottle and suprise, it still leaked. He called it junk and now that I know it works it's great. Thanks.

 

[monteperformanc]

This is getting beyond frustrating. After locating and purchasing the red angel stop-leak, an oil injector, a digital scale, and a new set of Mastercool gauges, I attempted to recharge my system.

My first disaster was I apparently had the low-side hose situated in the opposite direction, as the red angel was only going into the hose, not the accumulator. It would not take it all in so when I undid the hose to see what was going on, it shot it all over the car and the garage, like a volcano erupting! What a mess and a waste of $37.

So then I attempted to go ahead with the recharge anyway. I filled in about 1.7 lb of r-12 with the car off. I then started the car, turned on the a/c, and it would not cycle the compressor at all. I had to jump the pressure cycling switch connector to turn on the comp. and draw in the rest of the charge. I stopped at 3 lb. However, I then discovered that it was really 3.9 lb because the scale was reading differently with the yellow charge hose attached! Pressures on the gauge were about 45-50 low side, and 210 high.

So now I have too much charge in there, and I still have no a/c becuase the compressor refuses to run AT ALL unless I jump out that switch. I am assuming I have a bad switch, even though it was working last time I charged back in June. Now I am thinking that maybe I never lost and charge last time, perhaps the switch went bad.

I have spent over $500 on this already and this does not even include the R-12 which I got for free. Still no a/c. This may be the trickiest thing I ever dealt with on any car!

Is there a way to reduce my charge without having to completely evacuate and start over? I think I am getting low on how much freon I have left in the tank. Does anyone know how much those 30lb tanks weigh empty?