OK, so I finally recieved my AC guage set and vacuum pump. I drained and evacuated the system, put the Ester oil in the compressor, then evacuated the system again. It would create a vacuum of about 20 hg-ins or whatever the units are, and it would hold that pressure for a while after the pump had been disconnected.

I thought that things were going well until I tried to recharge the system. It took some freon, but not very much and very slowly. It seemed to be cooling just a tad bit, but only about 10 degrees when compared to the vent temp with AC off. When idling with max AC on, the gauge reading on the low side was about 90, while the high side read about 150. While the engine was revved up to about 1400 rpm, the low side read 70, while the low side read 175.

Any ideas about what I should do next? Thanks!

 

That vacuum should hold without dropping any for 24 hours. If it don't, it's leaking air back into the system. You should weigh the freon that goes into the system. It takes a certain amount and t is pretty important to be around that figure (i.e 2.2lbs) I don't know the exact amount off hand but you need a digital scale to be accurate. The amount should be on a sticker under the hood.

 

Thanks for the advice, rockfoot! I guess that the primary question that I have is why isn't the system taking any freon. Oh, I should add that the system did not los any pressure while I was testing it. I guess that I could evacuate it again and leave the pressure on for a day.

 

The gas goes in slow. Turn the bottle upsidedown, you get liquid. If you turn it upside down, it could cause problems as you are going in on the suction side and the compressor likes to compress gas not liquid... much like an internal combustion engine....

 

If the cutout switch that feels the superheat coming back to the compressor from the evaporator does not engage the clutch on the compressor or the low pressure cutout switch does not engage the compressor clutch, then the freon will not go into the system.... is the clutch engaging on the compressor?

 

The pressure in the system where the freon goes into the system has to be lower than the pressure at the source of the freon that you are adding....

 

I first hooked up a freon can that was about 1/2 full. It took this can fairly quicky, but when I hooked up a full can, it slowed down quite a bit. I had it hooked up for 15 minutes or more, and it only took about 1/2 of that can. Unfortunately, I do not have a hose that I can use to connect the freon can to the guage set, so I use a small quick-charge hose and cannot monitor low-side pressures. BTW, the tag on the vehicle calls for a 38 oz charge of R-12, so I need about 32 oz of R-134.

The compressor kicks in and stays on, which is kind of odd, because it was running with only a small amount of freon in it.

Oh, yeah, the system has been opened up and exposed to outside air. From what I understand, this can be harmful to the dryer and exp. valve. As you can see, I am still learning about AC systems, so sorry about all of the dumb questions!

 

ALL Air needs to be evacuated. That's what you are doing with the vacuum pump. Big problem with air is the moisture it brings with it when it enters the system. If the system was completely open to the atmosphere, then the vacuum should be pulled down to at least 28" and held there with the pump running for 4-8 hours......at least. The air and moisture gets entrained into the oil and it takes a while to get it out... but it will get it out of there if its left running long enough. 8 hours should be plenty.
The compressor will continue to run as long as there is pressure in the system above the low cutout AND the superheat is below the cutout. Either one of them will disengage the clutch if there set point is reached. I am pretty sure the two switches are wired in series.... that's just off the top of my head.... whether or not it cools depends on the condition of the compressor and the condenser and the evaporator and the expasion valve. I have seen expansion valve orfices clog up with nasty oil. When that happens, the high side (discharge) goes really stupid high...like 300psi+ and the low side kinda don't do nothing except stay steady. when you shut off the engine, it will still eqalize across the compressor....

 

I'm thinking that the reason that second can slowed down was the the suction pressure was coming up and eqalized with the can. Let it run awhile with the can valve shut untill the suction pressure starts going back down, then open the valve on the can. The gas should then go into the system.

 

If your system has been opened you should consider replacing the dryer and if it has an orifice tube replace it also.

 

If you have a FSM, there is a good guide in there about charging you A/C. One thing that they recommended and I can see where it would really help, is to place the cans of freon in a pan with 125 degree (F) water while you are charging the system. This would increase the pressure in the can over the suction pressure and cause the freon to go into the system a lot quicker.

 

Rule #1 in a/c work, if its been opened more than a few minutes it needs a drier. If you open a system thats charged the freon will expand for 15 minutes or so, this keeps moisture from entering, but only for a bit. You can also run the engine at 1000 rpms while charging, pressures drop as you increase rpm's. Why did you change over to 134 ? was it empty or low or was there a problem in the system, Also take a reading on your gauges with it not running, the pressures should be close to the same on both sides as they equalize. If thier close start it and take note of them, those pressures will tell ppl here what the problem is. Last thing you said you drained and evacuated the system, how did you get the old oil out ? If you just drained the freon out the old mineral oil is still there, this wont work, you cant mix oils and it only uses 4 or 6 ounces depending on compressor, if you just added it, its way to full.

 

A service manual might be nice, but I never have gotten into a hurry about getting one! I might have to try the water thing. Today, I tried again to get a charge in it. It took a little more and the air was actually slightly cool, but the AC is still far from working. One thing that I noticed is that there is oil squirting out of the low side when I disconnect the freon or gauge. Is this normal, or maybe an indication of a problem?

I will try the water idea, but if that is not successful, I will probably get a hold of my mechanic buddy and see if he can get it figured out.

BTW, thanks for the advice!

 

If your system requires R-12 refrigerant thats what you have to use. Using a R134 (1,1,1,2 Tetrafluoroethane) you have to use a different orifice tube in the system. R-134 is at a lower working pressure than R12. I make R134 and R125, AZ-50, R141b, R22, etc. I'm also certified to buy and work with these materials. You cannot no longer purchase R12 without an EPA approval card.
Im curious about you compressor have you checked your seals on the compressor shaft? They can wear out some of all of these refrigerants are made from HF acid and can wear these seals out. Next time when you get ready to place some refrigerant in there get some leak check and it should show you the pace where the leak is. Hope that I helped. Oh, and you never add liquid to the low side (the suction) of the compressor, it WILL damage it.

 

In response to loch's post, I have gotten a reading when the thing was not running. I will have to do it again to refresh my memory, but I know that the low side reading was very high (like 2-300, past where the guage registers), and I think that the low side was 150 or less.

I changed to 134, because the thing did not work and 134 is cheap! The compressor did not engage, so my guess is that it had a slow leak (didn't work too well last summer), and I should add that I have put a sealer in it. I tried that Freeze 12 stuff, but it did not work, which seemed kind of odd. A bigger problem maybe???

I did get some oil out of the system here and there, but probably not too much. I tried to remove the compressor to drain it, but after breaking a few wrenches and gettting angry, I decided that thing aint coming off unless it needs to! Is there any good way to get oil out of the system without draining the compressor? I added, well, too much of the ester oil.

One question: If I do not replace the dryer right away, will the system still work so I can do some troubleshooting for other problems? For the time being, I am not looking for a clean, prefect system recharge.