I installed a brand new A/C system in my 91 Mustang (compressor, condenser, accumulator, and all hoses and fittings) and when I began charging it last night the high-pressure side hose from the compressor to the condenser hose blew off.

I quickly realized that the spring fitting connection at the condenser wasn't engaged properly which caused the hose to disconnect in spectacular fashion once under pressure.

I reconnected the hose, ensuring the spring lock fitting was properly engaged this time, pulled vacuum for 30min and then proceeded to charge the system successfully.

My question now is, do I need to worry about the oil level in the system since the hose blew off or should I be ok?

The compressor was pre-oiled with enough for the entire system and I added UV dye to the low pressure fitting on the compressor before attaching the hoses. When the hose blew off, it sprayed dye all over the inside of the engine bay near the condenser connection.

Does this mean that I lost oil along with refrigerant and need to evacuate the system completely to measure and add more oil?

The system cools very well now but I'm just worried that now I'll run the risk of burning up the compressor if too much oil was lost in the hose mishap.

This is my first time tackling any A/C work so any help or guidance you guys could give me would be very much appreciated!

  • Only oil left would be in the evaporator, which would be 1-2 oz, i recommend adding 4oz of compatible oil.
    – Moab
    Jun 19, 2017 at 1:07

1 Answer 1


In short, yes you lost oil.

The question is how much? The purists would drain the system, but in your case that is impractical.

Suggestion. Find out the total oil charge for the system. If you can call the compressor rebuild er and see how much oil they charge it with. Now try to estimate how much oil was sprayed out during the big event. Difficult but you're going to have to use your judgement.

Let's say your capacity is 4.5 oz and you lost 1 oz. Then I would try to add some. If it was 0.5 oz then I might not. The smaller the oil charge the greater the impact of lost oil. Slight over oiling is not a problem so I tend to be conservative.

You won't necessarily need more dye as it is strong stuff.

Your old R12 system which I assume was converted to R134a typically has a larger oil charge, like 4 oz or so.

Generally a blow off will leave 50 percent or more of the oil in the system unless the breech was close to the compressor.

  • Thanks mongo! I really appreciate you taking the time to explain in such detail. Unfortunately I think this is a moot point now because I came home yesterday to dial in the low pressure switch to fine tune when the compressor kicks on and off and saw immediately that the spring lock fitting from the condenser to the evaporator had blown off! It seems crazy since I fully charged the system and drove it with no issues. :( At this point to be safe I think I'm going to just take it in to be evacuated and filled professionally since I don't want to ruin a brand new compressor. Jun 2, 2017 at 13:38
  • It appears that the actual spring is gone from the spring lock fitting that connects to the evaporator so I guess now I'll have to figure out how to get another hose since the system was a packaged R134a conversion kit... Is it at all possible to evacuate the system of all oil myself or is that something I'll need to go to a shop to have done? Thanks again for your help! Jun 2, 2017 at 13:44
  • I might try evacuation of most of the oil with N2 into the access of the system furthest from the compressor, and have it drain out on the side closest (and hopefully down hill from) the compressor. You won't get it all, but i might guess you will leave 0.5 to 0.8 oz in the system. If faced with that task, I figure I might use 2/3 of a 60 cu ft tank of N2. It's not expensive, ($9 for 60 cu ft on my account) but I wanted to give you an idea. As I said, if you have an extra oz or so of oil, it is normally not an issue. A friend with a N2 tank, or a rental, and fittings and regulator.
    – mongo
    Jun 2, 2017 at 13:58
  • It is something you could do yourself. It seems, that you have a beef with the kit provider. Oh, you could use 100% argon instead of N2, if that is any easier for you (and your friends). More often people have 100% argon for TIG and some MIG welding. Do not use a Ar/CO2 mix. N2 is cheaper, though. ALSO, there are AC flush products, which might help get the oil out. A little more expensive per purging, but it might be more doable. AZ and other places have "rental" units, and you buy the expendable. I would urge you to read the instructions first, as I have not investigated the use for this.
    – mongo
    Jun 2, 2017 at 14:02

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