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I recently bought a 2009 Honda Fit for my daughter. The A/C system has a major leak in it which I plan on fixing. As part of the fix, I want to clean out all of the oil which is in the system and replace it with new. As part of this, I want to understand the following:

  • How do I properly clean out the A/C lines of old oil? Are there certain solvents which I should or shouldn't use to ensure the lines are cleaned properly?
  • How much oil do I need to put back into the system once cleaned?
  • What type of oil is required for the Honda Fit A/C system (I understand there are several types and want to get the correct one)?

EDITORIAL NOTE: My intent is to do the work myself. I will not be taking this to a professional A/C person. I'm not looking for advice which tells me I should seek one out, because it isn't going to happen. I can appreciate this type of thinking, but telling me to "go to a professional" is not what I'm looking for here.

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Getting all the oil out of an A/C system is quite an undertaking. I do many A/C repairs and will take on the project of cleaning the system only if forced to do so. Debris from a failed compressor or other comtaminaties such as sealers are the most common reasons. The systems do just fine with the old oil if it is still clear. The best flush solvents and tools are made by Hecat inc. Hecat. I have not found a method that flushes the whole system in one pass. The method I use is to disconnect all the connections and flush each part or line one at at time. About half of the oil is usually in the compressor, it is removed and drained. The filter drier is replaced as oil is absorbed into the filter media and cannot be fully cleaned.

The oil is PAG, viscosty rating is 46, amount is 120ml, Sanden type SP-10.

Refrigant: 15oz of R134a

To install the oil put 1/2 in the compressor and turn it 10 times to make sure it gets distributed and does not lock up in the compression chambers. The rest of the oil gets distributed into the other parts. It gets moved around by the refrigerant so exactly were is goes does not matter that much.

Put it all together with new seals. Pull a near zero vacuum for 30 minutes, test for leaks. Feed in 15ozs of R134a then check the vent temp. About 40 deg F is usual.

  • This is a great write up and exactly what I was looking for ... I've seen videos which state exactly what you are saying: piece-by-piece cleaning. I don't know if, considering what you said, if I'll need to do a complete cleaning. There are two things which I'm worried about: 1) the amount of oil currently in the system (not having enough or putting in too much); 2) presence of contaminants in the system. I still have to check the compressor to ensure there's no issues there (lock up, etc). If none, I'll check the condition of the oil. If still clear, I may just roll as is. – Pᴀᴜʟsᴛᴇʀ2 Apr 2 '18 at 13:26
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1) The lines and every system component must be flushed so that the lubricant oil can be removed (except the compressor, receiver dryer and expansion valve: the compressor must be removed from the car and all oil should be drained from it, and that oil must be measured; the receiver dryer needs to be replaced whenever the system is opened for a long time, and the expansion valve, if clean, can be put back, otherwise replacing it surely won't hurt; never flush these parts). Since you didn't mention a compressor seizure and that the lubricant oil is designed to be soluble in the refrigerant, a closed loop liquid refrigerant flush (one where the machine maintains a steady flow of liquid refrigerant through a part for a certain amount of time, separating any oil that dissolved into the liquid refrigerant in the meanwhile) might be the answer (a compatible RRR station or dedicated flush machine is required for the job, along with the required adapters so that each system part can be flushed away). Your best option is to ask a licensed AC professional for an oil removal to be done through a system closed loop liquid refrigerant flush.

2,3) For this, look for the compressor in the engine bay and check the compressor's label. The oil type and quantity is usually written there, especially if it's a Sanden compressor (some Googling yields me what looks like a Sanden TRS scroll compressor for that car). Unfortunately, i don't know them. But, always begin by having a look at the compressor's label and identifying the car's compressor's model. Then, putting the oil back in is a procedure specific to each compressor. With some, you just put the whole system charge back in the compressor and then turn the clutch hub a number of times by hand so that it won't slug itself to death during startup; with others, you need to insert a precise quantity of oil in each part of the system and then let the engine idle with the AC on on max cooling for some minutes so that nothing would seize up. Again, a licensed AC technician is the best option.

  • I appreciate the attempt at an answer here. Unfortunately neither part of your answer really answers my questions, so maybe I need to clarify what I'm asking. Please take a look at my editorial note and additions in the question. – Pᴀᴜʟsᴛᴇʀ2 Mar 30 '18 at 14:56
  • The problem is, flushing the AC system needs dedicated equipment to maintain a constant flow of flushing agent (a solvent or liquid refrigerant) through the part that should be flushed, one part at a time. This equipment (a flushing-able RRR station for example) is expensive, there are many risks of messing things up and, in most countries, venting refrigerant to the atmosphere is illegal so that a license is required to handle refrigerants in any way. That's why, after explaining what needs to be done, i told you that it would be best to seek help from an AC professional for this. – Al_ Mar 30 '18 at 15:04
  • Well, venting isn't an issue, since it's a "well vented" system already. There's no refrigerant in the lines whatsoever and will not maintain a vacuum for more than four seconds. I have to find the source of the leak, first, though. – Pᴀᴜʟsᴛᴇʀ2 Mar 30 '18 at 15:19
  • To find the source of the leak, you have to charge the system up with refrigerant and inject dye (which seems to be usually put inside within the standard oil charge or during AC services anyways; the best thing you can do at the moment without even injecting anything yet is obtain a blacklight, turn it on and scan any system part until you see something glowing; another tell tale sign is any oily part, colored with a green hue or not; remember that PAG compressor lubricant oil is VERY different in viscosity, appearance and smell from motor oil, being very different in its chemistry). – Al_ Mar 30 '18 at 15:28
  • The system won't charge, so I'm going to have to take a different route. – Pᴀᴜʟsᴛᴇʀ2 Mar 30 '18 at 17:40

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