Replacing my Receiver/Dryer and have a question regarding the Pag oil Several years ago i replaced the compressor, condenser, and receiver dry and placed about 4 ounces of oil in the receiver dryer. It appears that one of my hoses is bad so this weekend I plan on replacing the hose and Receiver Dryer. Question. I do not know how much Pag oil to replace. What is the rule for replacing oil. Thank you.

 

I would like to know this also because I've got some A/C work to do.

 

I can measure the oil that comes out of the Receiver/Dryer that will give me a measurement. However, is it true when the system is evacuated all the moisture and oil will be removed? If that is the case I would need to add 7.75 ounces of oil to the closed system. What is the best method of doing that. The freon sticker states 2lbs or 32 ounces of freon. Any help would be much appreciated.

 

Little or no oil is removed when you pull vacuum. Somewhere I have a chart with the rule of thumb for adding oil when replacing different components but I can't find it right now. As I recall when replacing a hose it called for adding 1 oz. of oil. (Maybe even just 1/2 ounce.)

It's basically estimation and guesswork. The only way to really know how much oil is in the system is to flush out the old oil then add the proper amount. It's probably better to have a little too much tan too little. (Not enough oil and you can damage the compressor which will make a real mess out of things.)

 

Put the system under 30lbs of pressure and used water and soap to see if I could find a leak after 20 minutes of that no bubbles. Its been pressurized for about an hour now the gauge has not moved a bit. Should I inject freon with dye to see if the leak shows. Any next steps would be great.

 

If I remember correctly the you should pour about 2 to 3oz PAG directly into the receiver drier when replacing it. Balancing the oil can also work well (pouring out the oil form the old dryer and adding that much to the new).

Not enough oil will ruin the compressor. To much and the system will not (cool) work properly.

Refrigerant with dye is helpful for future leak detection.

You can actually pressurize the system with up to 200 psi dry nitrogen and soap connections, components, lines and check for leaks. Also the dry nitrogen will help remove moisture.

Before charging it with refrigerant pull a good vacuum 27inHg on it for at least 30 minutes to get out the rest of the moisture.

Charge it up and enjoy a cool cabin!

 

Just evacuated the system down to -29 waited two hours no movement on the guages. Tomorrow will replace the receiver/dryer, add oi, dye, evacuate, and replace freon. How can the system hold pressure and not have freon.

 

At the shop we would connect a dry nitrogen tank to the system using a welding regulator gauge set when the system is discharged. You can then pressurize the system to whatever pressure you want to soap connections and look for a leak.

If it holds vacuum overnight you are most likely sealed. Some leaks appear though under pressure, usually hard to find slow leaks.

 

System charged working good for now. Will report back in a couple of day. Thanks to all for your help.