DIY A/C repair, compressor replacement, flushing, and amount of oil added
 

With all the Sanden mounting kits I have been selling, I can't help but think that some are being installed and charged by someone other than an experienced A/C shop technician. There are strict procedures that have to be followed in order to have a quality, long lasting Sanden conversion. I will share the things that I know are important, and I am asking the experienced A/C techs here to add to/edit the list if needed. These are not in any particular order.

1) It is important that before installing a new compressor, that the evaporator and condenser (along with any existing hoses) be flushed out with a good quality solvent made for that purpose. The use of nitrogen (or other dry gas such as C02) is recommended over shop air. However, dry shop air can be used as a last resort if that is all that is available (no need for debate about this, as it is covered on other threads). The evacuation should boil out all the moisture in the system.

2) Receiver/drier replaced with a new one, and installed after flushing is done.

3) Compressor oil should be drained and measured. The proper total amount of oil should be distributed between 2+ units (compressor, drier, evaporator etc.), or just injected in the high side during the charging process. The new compressor should be turned (center hub, not the pulley) 10+ revolutions to distribute the oil within the crankcase of the compressor before installing it (much easier before than after).

4) Leak check performed. I use a dry gas with soap and water in a spray bottle. There are other methods for leak checking described on other threads.

5) As far as the proper amount of oil, I believe that the standard is 3.5 oz per pound of refrigerant. Because of the smaller volume of the Sanden compressor (separate oil sump), less refrigerant and oil is required. Six to eight ounces of oil/dye total for a 123 with a Sanden and 134a should be adequate.

I am sure there is other things that should/could be done, but the above are the important ones. Please feel free to add to or correct anything. I just want to share the experience with these systems that I have gained by working with my local A/C shop. I/we have done almost a dozen in the last few years. In the beginning they were R4 jobs, but those compressors turned out to be a bad investment.....Rich

you should change the recommendation to 2 oz per pound of refrigerant capacity.

6 oz per pound would equate to 18oz for the 123... kinda overkill for sure.

I have started using CO2 for my flush gas. it's plentiful, and affordable. the tank is about 120, the regulator is around 35. if you purchase a smaller refillable tank, you don't need to buy a separate regulator, as one comes with the small tank.

I talked at length to my A/C tech (Chris) today. I made a mistake in what I heard from him about the amount of oil required for my system. I thought I heard 6 oz per pound, but it was 6 oz total for my system. His book (and what he was taught) says 3.5 oz per pound. Based on amount of refrigerant required on sticker for the 123 chassis, 6 oz would be the proper amount (all things considered) for a 123 with a Sanden using 134a. The stock R4 does not have a sump, so all the oil recirculates with the refrigerant (larger volume than a Sanden). The Sanden would require less oil for the entire system. It is also recommended that the entire oil charge NOT be in the compressor at start up. It is recommended that the oil be put in 2+ parts of the system (compressor, drier, condenser, evaporator etc.). I believe it is easier to just drain out as much of the oil as possible from the compressor, and just inject the proper total amount in the high side during the charging process. However, oil could be added to the drier easily. I have heard others say that the 6 oz of oil supplied with a new compressor (in it's sump) is adequate, and no more oil needs to be added. I would feel better having some oil in the compressor, and some mixed with the refrigerant. Please feel free to dialog on this subject, as I am always willing to learn.....Rich