Funny noise

[Glen B]

I have a 2019 ram 3500.
From time to time I hear what sounds like a compressor that comes on for about 10 seconds and then goes back off.
I don't have any air suspension on the truck.
The only thing I noticed is afterwards my def gauge looks like it moves.
I'm a converted Ford guy so not familiar the the noises of the Ram.
Any insight will be most appreciated.
Please be kind.
Thanks

 

[Richard320]

You ought to ask over at https://hdrams.com. That's where the big boys hang out. This is 1500s.