"UZI" Air compressor sound....
 

So every 11-12 seconds (by my count) there is an air compressor "uzi" sound coming from my engine that lasts for a second each time. At first my reaction was to check the air compressor for the SLS air suspension in the rear...no sound coming from there.
I have no secondary air SAI on the truck, so what could be possible culprits?

A/C compressor cycling on and off due to low refrigerant maybe?

Thanks...Thats a possibility... Have not ran the AC in 6 months or so...
Any ideas on how to check the refrigerant level. I will search, but will more than likely go to the shop for this one.

You need gauges. You can watch AC compressor clutch. Or just turn off and see if it stops the cycle. One trip to the dealer for this will pay for a set of gauges.

SLS compressor and valves are not as noisy, but here's pix of them just in case. Disconnect C0811 for testing, kills pump and three valves.