You didn’t provide much information about your crawlspace – you have to check / determine its condition, try to find the source of that moisture and eliminate or at least minimize moisture penetration (high water table, poor grading on exterior, foundation cracks, leaking plumbing, etc.).
Solution could be as easy as plumbing leak repair or more complicated; involving foundation repairs, drain tile and sump pump installation and / or improvement of an existing drainage system, moisture barrier (plastic foil) installation on the crawlspace floor and / or floor framing, sealing of all floor penetrations, air ducts, etc. Additionally you should consider mechanical vent installation in one of the two openings, which would force air circulation.
If you’re in Michigan, passive (non mechanical) vents allow more humid air into the crawlspace instead of discharging it beyond the crawlspace – they simply don’t perform well in a high humidity environment.
Somebody has to evaluate your crawlspace / crawlspace ventilation and then pick the right solution for it.
Let me know.