Engine bay - High pitch whining noise

[Dub1796]

Anyone else ever notice a high pitch whining noise from their engine bay while washing the exterior of the truck or when it rains? My truck is off and in complete rest mode, and I use a standard pressure garden house. 

 

It sounds like a computer is in pain lol

[Dub1796]

20190406_205149_1.mp4

 

This is the sound it is making

[B R A D]

Mine did the exact thing last weekend. Had ran it through the local tunnel wash. When I got home I was gonna check oil level and wipe clean and spent 5 minutes looking up in the trees for the noise before realizing it was coming from the engine bay. After about 10 more minutes or so had passed it finally went away. No earthly idea what it was or could be.

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[Bama14Z71]

My 2014 Silverado was doing this today while I was washing it with garden hose. Any idea why?