Changing an A/C Compressor – What Year Did They Stop Using R12?
DennisB WiseAutoTools.com © Summary: What are the common steps in changing an AC compressor? What year was the last for R12 before the switch to R134A? This and many other AC questions answered by a Master Tech with 30 years hands on experience working on cars in Florida.
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Whenever any compressor is locked up there are things that need to be done. A locked compressor many times will contaminate the system putting debris from the failed pump into the lines. For this reason a system flush should be performed. Some components cannot be flushed. The expansion valve or tube cannot be flushed. The dryer or accumulator cannot be flushed. These items are replaced only. The amount of oil for a system is partially determined by what’s being done and which components are being replaced. Also taking into consideration that if flushing ALL of the old oil will be removed as opposed to just replacing a dryer and expansion valve; by just replacing components there may be some oil in the rest of the system. If the old compressor was locked up (siezed) then flusuhing is recommended. If the old compressor just leaked and the oil in the system doesn’t look dark or burnt, a flush may not be necessary. I would notice if oil is present when taking a line off to get an idea of whether the system is properly oiled or not. Typically, it’s common for refrigerant to be added over the years. If oil wasn’t also added in the system, it could be dry because the oil circulates with the refrigerant and when there’s a leak both leak out. On the other hand it’s possible that somewhere along the line too much oil could have been added.
How much oil should be added to an AC system?
Specifications for oil amounts may be different so that needs to be looked up for each particular vehicle. Viscosity (thickness) also varies. A rule of thumb is 1 ounce per component. The compressor may need more. For instance the 1994 Ford Ranger specs say that 7 oz of oil is needed for the entire system. Repair procedures will have you draining the oil out of old components that have been removed so you know how much to put back in with the replacement part. It’s not that simple, due to the different scenarios I mentioned above. When intstalling a replacement AC compressor, you always put the oil directly into the suction side of the compresssor and you don’t rely on just adding some with the charge. The lubrication it needs may not get to the compressor before damage starts to occur from friction and from heat. Also before running the system, the compressor should be manually turned 10 revolutions by using a socket and ratchet on the nut on the compressor shaft located in the center of the clutch plate. This will prevent oil from damaging the compressor on start up. The compressor cannot compress liquid so this helps disperse the oil. Once the oil is mixed with the refrigerant and circulates with it there will not be an accumulation of liquid from pooled oil. It’s also a good idea to use oil with UV dye or to add some dye if the oil does not already have it in it. This will assist in finding leaks if and when there is one. It’s much easier to go ahead and put it in when working on the system than to have to add it later and then wait for it to circulate through the system to reveal the leak. PAG oil is used with R134A. Make sure to clean up any excess UV dye after the job is completed to help avoid a mis-diagnosis alter. Read on the bottle to make sure the oil being used is PAG or at least compatible with 134A systems. The wrong oil can cause problems like clumping and restriction of proper flow. This leads me to a question when working on an older vehicle’s air conditioning sysetm. Read on for more information on servicing an AC system.
What year did they stop using R12 and switch to 134A?
When was the was the last year car manufacturer’s used R12 in the United States? The year was 1993. In 1994 R134A was implemented. Car manufacturer’s starting using R134A in 1994 on vehicles sold in the USA. R12 refrigerant was still used because stock piles were made in anticipation of the stop of production. Also shops were able to capture some R12 for awhile with their recovery and recycle machines. This made the cost of R12 refrigerant spike because most car owners did not want to go to the extra expense of converting their air conditioning systems over to 134A when they only needed a system top off. Over time the use of R12 became less and less. Shops ended up converting their older R12 machines over to 134A so they could agian be used.
So now what?
OK so you’ve got the new compressor on. What do the gauge readings mean? See our article on AC Gauge Readings Explained. Be sure to check out both pages because the images of gauge readings are on the second page. Knowing what both high and low readings are necessary to really know what’s going on with a system. If after doing an AC job the it’s stops blowing cold, there could be a refrigerant leak. Remember the UV dye mentioned earlier? This is where the dye can come in handy. Also use an electronic refrigerant leak detector to help pinpoint leaks and help avoid replacing parts that aren’t really faulty. Beware that some Freon leak detectors are notorious for false alarms so double check to be sure there’s really a leak. As already mentioned, the use of UV dye is a good way to verify there’s really a leak. See our article on Finding Refrigerant Leaks for more information.
Want to learn more about car AC? See the Air Conditioning Repair section here at Wise and also check out even more Car A/C Articles at DenLors Tools. Need the right tools for car AC repair? We’ve got you covered.