AC R12 system oil

[Q45tech]

The system contains approximately 8.3 ounces of oil and whenever a component is replaced oil should be added based on the amount that was in each component.Evap 2.9 oz.;condenser 1.5 oz.; dryer 0.2 oz., low press hose 0.2 oz., compressor 3.2 oz,.R134a are different in type of oil and amount!After replacing the compressor, hose, dryer, and condenser last summer I thought I got it right.............somewhere along the way I miscalculated and used 2.0 ounces [?] too little.

I have been chasing a 3-4F higher than spec condition all summer finally on a guess I added 2 ounces of oil to the system, guess what...........the temp dropped 4F [meeting spec].

What I forgot is each time you vacuum the system, about 0.4 oz. gets sucked out and nothing gets added unless you manually add oil. I probably have vacuumed the system 6 times without adding compensating oil over the last few years.

Now I have to gingerly add in 0.25 ounce increments till the temp rises from too much oil then vacuum it out.

My guess is the exact sensivity to too much oil is probably 0.4 ounces more than spec [5%] as -25% = 4F plus who knows how much life I took of the compressor operating with low oil?

The spec is 45-47F after 20 minutes of cruising. Summer is over.

The problem is you have to dissassemble every part of the system and weigh the oil to get it right or my temp method.

It has always amazed me that my evaporator has lasted since the car was built!.....Jan 04 will be 14 years but same with heater core and lots of things.

[TechGizmo]

Very good info Q45.My mechanic checked the AC operation on my J30 and said it was a bit noisy, because of a lack of lubricating oil. I am planning to have the AC serviced next spring.