If RH is your problem I'd work on the exhaust/air flow side.
If the temp drops RH goes up, but if the temp goes up then RH goes down.
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It seems that you're wanting to dehumidify the grow by running the AC, but that you think your RH is high based on temperature fluctuations, so to me it seems you're fighting yourself. Trying to use the tool to dehumidify that is causing high RH, seems you need an additional mechanism to control RH while maintaining temp. I see it as too seperate processes. Temp mgmt, and RH control. Use your AC to get your desired temp but if your air has so much water in it that when you drop temp you have RH issues, then you'll need to either get another deheuy or exhaust better. If your outside climate is humid, then dehuey is your only bet.
If you want to try to use your AC as a dehumidifier, id just exhaust it into your grow room instead of out the window.