I have a Dell 90W AC power adapter, DP/N 0C9HYX, apparently good for any of 3 Dell laptops that I own. It's wrapped in clear plastic, but rather tightly, not like packaging used only for shipping. Am I supposed to leave the clear plastic in place (in case it's protective or something) or remove it before using the adapter (like to prevent overheating)?
Yes it is just a protective clear plastic cover for shipping.
You can remove it if you want.
If not it should not produce any added temperature to the AC.
Microsoft Registered Refurbisher Microsoft Registered Partner Windows Operating System lifecycle fact sheet Lifecycle begins when released and ends when no longer supported HP EliteBook 8770w i7-3630QM 32GB HP ZBook 17 G2 i5-4310M 16GB