Tales from the helpline: When they don’t know, what they don’t know!
By Richard Hawkins, MACS Technical Contributor
Last week, my topic of discussion for the MACS blog was a tech call about an A/C system which was plagued by a huge oil overcharge. The interaction with the technician illustrates some issues which tend to be encountered frequently with inexperienced techs.
Note: This was a single system with a 1.8 lb. refrigerant charge and 8 ounces of oil. With the 22 ounces of oil that was estimated to be in the system, that was about 2 3/4 times too much.
When I asked why he thought the compressor needed to be warranted and replaced, his reply was that “… it wasn’t controlling the pressures properly.” (The system was running about 365 to 375 psi with an ambient temperature of 80 F.)
I explained that this system utilized a fixed displacement compressor with no mechanism to control any pressures. It’s just a pump that circulates refrigerant through the system. His reply was something along the lines of “No disrespect to you, but I’ve talked to several guys around here that do A/C work and they all think it is the compressor. I don’t see how a few extra ounces of oil are going to cause the pressures to skyrocket like that.” To which I replied, “That system doesn’t have just a few extra ounces of oil in it.It has overtwo and a half times as much oil as it is supposed to have.”
That must have gotten his attention, because his next question was, “So what do you suggest that I do?” My answer was,” You need to get the correct amount of oil in that system. So. you need to remove all of it and install 8 ounces. That’s going to involve draining the compressor, flushing the system, replacing the accumulator (because it can’t be flushed and it acts like a sponge and should have been replaced anyway), and replace the orifice tube because it still has the original one in it. His reply was: “Man that’s a lot of work you’re talking about. I’m going to have to think about it. Why can’t I just remove enough oil to get it down to 8 ounces?” To which I replied, “We don’t know for sure how much is in the system. Our math has involved some speculation. It’s best to get it exactly right and to install a new accumulator and orifice tube”.
I was curious how things went, so I called a few days later. He said he decided to just remove some oil and see if that made a difference and he was able to get it to cool much better. That wasn’t the best way to do it, but at least he learned that the compressor wasn’t the problem and hopefully used the experience as a reminder to be more careful about condemning compressors and how much oil he installed in systems he worked on in the future.
Learn more about the Mobile Air Conditioning Society (MACS) at www.macsw.org
