Continuing the saga:

I forgot to describe the exact symptom I have been experiencing. Here goes. After the AC failed suddenly on my '04 Corolla, I was advised to replace the compressor. When I picked it up with the new compressor in place, the AC seemed to be going blazes, but in the next couple of days it became weaker and weaker. I took it back and they recharged it. Again, seemed to be cooling very effectively at first, but it degraded over the next couple of days. When I went back, they recommended replacing the compressor, by process of elimination, and they said they were certain there were no leaks.

I decided to wait until the weather warmed up somewhat so that I'd feel more confidence in my evaluation of new results.

Today the weather started to warm up. I printed out the answers and comments from my other question and took the car back to the shop. Based on advice given at the other thread, I asked what was wrong with the compressor that failed. The manager just shrugged and said it was no good. I asked how they were able to determine that there were no leaks, and he said that when they connect it to the machine for recharging, step one is to suck out the refrigerant that's in the system, converting the gas to a liquid in the process. The manager said that the amount withdrawn was exactly the same amount they had put in the previous week, and that's how he knows there are no leaks.

Is that logic valid? Today they agreed to check the dryer and the expansion valve but in the meantime I would like to understand the situation better.

  • if you have no confidence in them...take it to a different shop ..dont tell them of your previous experience with the other shop have them inspect it ..tell them of the cooling problem your having...just get a second opinion Jun 14, 2018 at 9:06
  • @EdwardEvans - Thanks! Question: Is it fair to the second shop to not tell them that I just had the compressor replaced? Also, won't they see traces of the dye Shop #1 put in? Jun 14, 2018 at 13:11

1 Answer 1


If they are truthful and pulled out as much refrigerant as they put in (by weight), they are spot on. They can weigh what comes out of your system to see how much there was. If it's as much as they put in, then there would be no leak.

  • Thank you. Can you think of another possible explanation for why the cooling ability degrades gradually after a recharge? Basically, I need guidance for walking them through a reasonable diagnostic procedure. Jun 8, 2018 at 21:17
  • 3
    @aparente001 - If they are a reputable shop, you shouldn't have to lead them through anything. Let them do their job. If they are good at what they do, they will still follow what you tell them to do and it will cost you more money. If you go back to them and ask them why they did all of that, they say, "Well, we told you in the first place, but we did what you told us. This is on you." Just let them do their job if you trust them. Jun 8, 2018 at 21:41
  • I don't know them well enough to say that I trust them or I don't trust them. What I've been finding is that they have trouble answering my questions, such as, what's the basis for recommending that I replace the condenser? I did ask them today if they will guarantee that by replacing the condenser the AC will be fully operational, and they didn't want to answer that question -- they said they want to look at it first. That is a bit of a red flag, since previously they said the ONLY thing left to do was replace the condenser. (I moved to this area recently.) Jun 8, 2018 at 22:23
  • Question: if refrigerant amounts can be precisely measured in this way, then why do shops put dye in? I don't understand the reason for the dye. Also, if there is moisture in the system, won't the weight of the liquid water skew the results? Jun 14, 2018 at 13:13
  • @aparente001 - Weighing the refrigerant tells them if there is a leak or not. The dye tells them where it's at. Jun 14, 2018 at 17:20

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