mini split blowing tepid air no matter mode or settings
My 6-year-old Fujitsu is blowing room temperature air. I’m not sure how long it’s been doing this, because I have another unit on the floor above that is picking up some of the slack, and my wife likes a hotter house so has a habit of turning the suspect unit off any time I am not around (and usually even if I am). Bur we just came back from camping, and it was making an odd sound in dry mode, something I’d describe as half hiss, half buzzing. I tried switching to cooling mode, and the sound went away (or I couldn’t hear it over the higher fan speed), but still no cold air. I switched to heating mode, and the air coming out didn’t change temperature. My first thought was a leak and low refrigerant, but on the energy monitor I can see it does ramp up in power when adjusting the temp setting. Usually if the refrigerant is low enough to cause a lack of cooling or heating, that means the compressor isn’t running.
I know it’s impossible to diagnose remotely, but any suggestions of things to check? The filters were cleaned fairly recently and look ok. How about how to find a competent HVAC company? The company that installed it wired it wrong, and took them five separate visits to fix it, and even then they didn’t actually figure it out but had it told to the service guy by Fujitsu support, which he initially argued with. I heard the one side of the conversation and it was cringeworthy. So I’m not inclined to ask them for help.
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Replies
Sounds like you lost the refrigerant. Sometimes these develop pin holes in either the line set or the indoor coil over time. These are not easy to find and replace, sometimes it is simply cheaper to get a new unit.
If you are adventurous and have access to high pressure inert gas (I use the argon tank from my TIG) you can leak test yourself and try to locate the leak. All you need is a gauge set and the proper high pressure regulator, both are a couple of bucks from your favorite on-line retailer.
Most minisplits have a pump down procedure where you can reclaim the refrigerant in the outdoor unit and close the service valve ports to keep it there. Once the service valves are closed, the line set and indoor unit are isolated and you can pressure test to find the leak. If you are lucky, it is just a loose fitting, if not you'll have to replace the line set or the indoor head. If still can't find the leak, then it is in the outdoor unit at which point might as well get a new unit installed.