I've got this problem as well. Funnily enough mine is only a problem when the phone is flat and I try to charge it while it's off. But after trying to charge the phone when it's off and it says there is moisture in the port I try turning it on and plugging it in straight away and now it thinks there is moisture in the port when the phone is on as well. Obviously I try my best to never let the phone go flat but it always seems to be unable to charge when I need it the most! As most people with the issue say, the phone has never been wet. I had the error come up on a rainy day about two weeks ago while it was in my pocket (still didn't get wet at all) obviously the humidity set it off. I've owned plenty of phones and none of them have ever blown up or died from allowing me to charge them on a rainy day. It's just crazy that a $1400 phone (Galaxy S9+) can have such a critical flaw, clearly the design whether it's hardware or software that is supposed to detect a wet charge port is very prone to breaking. I think this is plain unnacceptable to add such a flawed feature to a critical component of a phone.
This is a fairly well documented problem ranging from the S7 all the way to the newest S20 and Samsung seem to have absolutely no intention of actually fixing the problem and keep bringing out new phones exhibiting the same issues. I've read a bunch of threads from frustrated users about the issue and the advice they get is to factory reset the phone (pretty well never works) or to just side-step the issue and buy a wireless charger. Seems like they have no way to fix the problem... how about giving users an option to disable the feature entirely I'm not a fool I can tell when my charger port is wet and dry it before charging it, I would gladly give up my warranty to download a patch that removed this useless "safety feature".
Sent Samsung an email through their support page about a week ago and have not heard anything back. I honestly can't believe the phone manufacturer with literally the BIGGEST market share in the entire world up until last year has such a critical flaw in their flagship phones. I've owned nothing but Galaxy's since the S2 but probably won't buy another until they sort this rubbish out. <edit> Rant over.
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