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The first technician that came over thought the problem was the condenser capacitor, which was old, I replaced that but didn't fix the problem. All the components were running, including the compressor and both fans inside and outside but no cooling. He said the refrigerant pressure was OK but...

The second guy said the refrigerant was completely gone (which means the first guy was lying and will never call him again) and thought the leak must be withing the evaporator coils based on a known problem with Lennox that even has a class action lawsuit. But that was a red flag to me because he just wanted to replace the coils on a mere suspicion and no definitive leak find. So I won't be calling that guy anymore either.

I brought a third guy who did a nitrogen test but could not find any leaks. We sprayed all the brazed connections with microleak detection fluid, no bubbles anywhere, no hissing noise, no nothing. Both on the condenser side as well as in the coils. He said basically just recharge the system. Here is the pressure gauge readings that held for like 45 min.

enter image description here

I have enough leftover 410a in a tank from last time the compressor was changed, so it would not be expensive to just wing it and recharge to see what happens. But the test results are not consistent with the incident of losing all the refrigerant in the system. So is there anything else that could explain this mysterious loss of refrigerant?

amphibient
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  • That, (which should cause them to lose their US-EPA license to handle refrigerants) Or the leak is from where the gauges are connected to. – Ecnerwal May 12 '23 at 18:42
  • I only have the guy's phone #, I regret not having him show his license and taking a picture. I have his phone number but he is ignoring me now – amphibient May 12 '23 at 18:45
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    @Ecnerwal, I assume you refer to the last sentence, which I deleted as paranoid, as your "that" – amphibient May 12 '23 at 18:46
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    If it isn't the lineset then you're pretty much sol. It's in one of the coils. I guess you could try some leak stop, but that's new system time. Pressure testing with an analogue meter? Don't call them back either. Nitrogen test is if it holds pressure (because it's benign and what you have on hand to do the soldering), and when to crack the vales open for the first time, not to *find* a leak. Need to put some in the system and use a sniffer. Leak stop is BS though. You either fill this system every year or replace it. – Mazura May 12 '23 at 20:13
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    "I have enough leftover 410a in a tank from last time the compressor was changed" Just a note : *you* can put *your* refrigerant back in the unit. *They* can't w/o having it "recovered". .... Also, what? "from last time the compressor was changed".... it's done, bro. Finito. New unit time. – Mazura May 12 '23 at 20:23
  • `having it "recovered"` there is nothing in the system to recover – amphibient May 12 '23 at 20:25
  • With "the last time it was changed", I was assuming it was a recovery tank. *They're* not supposed to be charging a system with a leak. But *you* don't have any certification to jeopardize.... using a little bit to find a leak is better than just arbitrarily charging a system every year. Hooking a gauge set to it shouldn't completely drain the system, unless the schrader vales are bad. If they didn't remove them when they soldered then they're compromised. – Mazura May 12 '23 at 20:34
  • https://www.amazon.com/freon-leak-detector/s?k=freon+leak+detector - Smokey the Bear says if you're not going to try to sniff it after you fill it again, then that's kinda a dick move. "just wanted to replace the coils on a mere suspicion and no definitive leak find" assume you found the leak in the coil, now what? Replace the coil? On a system that already has parts replaced? With known red flags? "not finding leak in HVAC system" using a sniffer? Nitrogen is how you know there's a leak, not how to find it. – Mazura May 12 '23 at 20:47
  • @Mazura i really have a hard time following what you are saying -- are you one of those people who say just buy new everything because it is irrepairable ? – amphibient May 12 '23 at 22:52
  • the leftover refrigerant has never been used, brand new leftover in a tank. i think you make some baseless assumptions and then go off of them – amphibient May 12 '23 at 22:54
  • "parts-swapper". Parts that I don't are evaporator coils, condenser coils, sealed units (compressors, so pretty much the entire condenser other than contractors, capacitors and the fan), and anything on a fridge that has to do with its cooling. All in all, just saying that if they didn't have a nitrogen sniffer... then what they doing? "We sprayed all the brazed connections with microleak detection fluid" that's the lineset : 50/50 chance that works. 0% chance on the coils. Never heard of anyone ever having actually fixed a coil. All a sniffer will tell you is the coil is bad somewhere. – Mazura May 12 '23 at 23:45
  • Kinda disappointing that the best we have for [Is it possible to detect and repair a refrigerant leak in my HVAC system?](https://diy.stackexchange.com/questions/21101/is-it-possible-to-detect-and-repair-a-refrigerant-leak-in-my-hvac-system) is 'call a guy'. *How do I find the leak in an HVAC system if all the refrigerant leaked out and a nitrogen test didn't work?* +1 – Mazura May 13 '23 at 00:10
  • [Should I replace whole system or just leaky component? {closed}](https://diy.stackexchange.com/questions/195314/should-i-replace-whole-system-or-just-leaky-component) *on a 17yo system?* – Mazura May 13 '23 at 00:17
  • [If an AC guy checks a system and finds it 100% out of refrigerant, what is the correct next step?](https://diy.stackexchange.com/questions/113916/if-an-ac-guy-checks-a-system-and-finds-it-100-out-of-refrigerant-what-is-the-c) "The HVAC service came out and this time found the (king?) valve was leaking; sealed *the cap* with teflon tape; worked 2 y" ... check the schrader valves, the valve seats of the shut offs on the condenser (that they didn't heat shield properly?), and the nut holding in the orifice at the evaporator coil. You ever get hissed at taking off any of those nut covers? – Mazura May 13 '23 at 00:29
  • @Mazura not anymore. It's illegal to service your own refrigerant system without licensure *and* recovery equipment, unless you use certain exempt refrigerants, which is a good reason for a DIYer to select systems which use such refrigerants. I'm sure the licensure prohibits you from dumping refrigerant into a known-broken system. – Harper - Reinstate Monica May 13 '23 at 00:56

1 Answers1

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This doesn't explain the loss of refrigerant, but is another troubleshooting tool.

There's another type of leak test that may be better than the N2 test. You need to have a running system to use this. They add a pound or so of some sort of dye to the system, and let the system run - the longer the better. Then the tech comes back with a UV (I think) light and looks for any signs of the dye (that fluoresces under UV).

Only shortcoming with this test is that if the leak is outside in a place exposed to rain, any precipitation will tend to wash any dye off.

SteveSh
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  • You have to sniff or look for something, and it isn't nitrogen, +1. – Mazura May 13 '23 at 00:00
  • Have you checked the compressor and the service valves, they can leak as well. Be sure to check the compressor terminals where they come out of the can. – Gil May 13 '23 at 00:22