My compressor failed so I am replacing it with a new one. I have all the necessary tools - vacuum pump, manifold gauges, flush kit, compressed air. I have read the Haynes Airconditioning manual, but I still have a few questions.
The manual mentions that the whole system can be flushed at once by blowing the solvent through the low-side hose and collecting it at the high-side hose. I don't understand how this will remove the contaminants. Won't the contaminants and the solvents remain trapped at the low points in the system? I do not see how the entire system could be flushed without flushing all the parts and hoses separately.
I am unclear about the oil. My new R134 bottle says the oil is included. Does that mean I won't have to mix any oil to the refrigirent. What about the compressor? Does it need separate oil? I don't see any oil reservoirs on the compressor where I can add oil.
It can't. To do it right you have to take everything apart, and throw away the dryer or accumulator (depending on which one you have) and throw away the orifice tube or expansion valve, depending on what you have, and replace them.
replace ALL o-rings with new ones, and make sure they are the o rings that won't disintegrate in the presence of PAG oil. (get them from an AC shop)
If this was an R12 system, it won't have barrier hose. You can use the existing hose if your a cheapskate (I was) but it will leak at a very low level (ie: you will have to refill the system probably once a year) This trick only works because the existing hose already has a little bit of oil driven deep into the rubber and that helps to seal the hose - brand new non-barrier hose will leak like crazy if you use it in a R134a system.
Also if this was an R12 system it will not be as cool. Where you will really notice this is when airflow through the condensor unit is low, such as at idle. You can replace the condensor with an aftermarket one that is more efficient, like a parallel flow unit, which will restore cooling.
Fush each tube including the flex lines with at least a quart of mineral spirits and run at least a minute of compressed air through to dry out the mineral spirits. There is a flush gun that makes this process much easier, that you can buy. Make absolutely sure that the compressed air your running through this is dry, not oiled. (many people run oilers on their compressed air lines to keep the air tools lubed) Also make sure it's got a water trap.
Return the refrigerant to the store. The pre-mixed stuff is rediculous.
Since this is a new system and your R134a you want to use PAG oil. Ester oil is for retrofits where they are not replacing the compressor or taking anything apart, and crossing their fingers and hoping the works don't blow over the mountain.
There are 3 different PAG oils If your system came from the factory with R134 in it, there will be a sticker somewhere specifing which grade of PAG to use. If yours is previously a R12 system, then it probably doesen't matter much which PAG oil you use.
When you do this, once you have the system completely bone dry, and all the hoses back together, before you put the compressor in, pour a little oil into it's ports and turn the compressor to distribute the oil inside, so the startup isn't dry. Once the compressor is fitted, if you have a system like a GM system where it's got an expansion valve, before you put the valve in you can use a funnel and pour the oil down in there. (since the pipe points up) the oil mostly hangs out in the accumulator or dryer, so you can also pour it in there.
Pull a vacuum on the system for at least 2-3 hours. Overnight if you can, is even better. This will remove residual water as well as boil the water out of the PAG oil (which will suck it up wherever it can get it)
Those are very valuable pieces of information that even the Haynes manual did not mention. Thank you very much. I will be attempting this work in the next few days, and will post the outcome.
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