YACT: When you vacuum out a car A/C does the compressor oil get vacuumed out too?

[Shawn]

How are you supposed to determine how much oil to put back in?

 

[Sluggo]

I think the refrigerant has the oil for the compressor in it.

 

[resinboy]

nope, the oil lays in the bottom of all of the components in the system: however when running, SOME of the oil gets circulated in the system. The compressor has a reservoir in the bottom of it, so when changing a compresssor, you need to drain it, measure what you took out and add a couple of ounces more ( due to normal system loss). Too much oil, you slug the system, too little, compressor says "see ya". There are charts as to how much oil to add for a particular component.

 

[Rogeee]

resinboy hit the nail on the head, in my experiance over the years I have concluded that if the AC system has been drawn down (evacuated down to at least 20 inches of mercury) more than twice since the last time fresh oil was introduced, then adding oil will be required.

I own a AC recovery station, typically I do not add oil after a repair requiring a system draw down unless the oil recovery container fills more than 1/2 ounce of oil which I have yet seen.

 

[Shawn]

Originally posted by: resinboy
nope, the oil lays in the bottom of all of the components in the system: however when running, SOME of the oil gets circulated in the system. The compressor has a reservoir in the bottom of it, so when changing a compresssor, you need to drain it, measure what you took out and add a couple of ounces more ( due to normal system loss). Too much oil, you slug the system, too little, compressor says "see ya". There are charts as to how much oil to add for a particular component.

How do you drain the resevoir? Flip it upside down?

 

[Shawn]

If the oil has been exposed to the atmosphere for some time (a few months) should it be replaced? Also I just got a new dryer and I think you are supposed to add some oil anyway correct? Basically I need to reopen the system to replace the expansion valve. I think I am going to buy my own vac and vacuum it myself since it is expensive to keep taking it to a shop. Anyone know where to get a good deal on an ac vac and ac gauges (high and low pressure)?

 

[resinboy]

thanks crustyoldman: 30 years of doing this stuff will learn you a couple of things 🙂

shawn: yup, remove the compressor, some actually have a drain plug: most do not- hold it with the ports pointing down and ( if it's not seized) spin the compressor over slowly by hand to pump out the oil.
Always a good idea to change the dryer when a system is opened.
I remember they made a cheapo air operated vacuum pump: don't know how well they work.

 

[Iron Woode]

I will be upgrading the AC on my 1987 Crown Vic this summer to r134a. I have to replace the evaporator anyway so I am getting the whole thing upgraded. The kit is only $75.00 CDN and includes a new fixed orifice tube. The evaporator R&R is going to cost me big though.