Electronic sounding clicking noise from motor when idle 99 denali

[Genn15]

Whenever I'm sitting idle my denali makes a strange clicking noise from the front end for about five or six seconds and then stops and then it will do it again a few moments later. It's not metal on metal or grinding gear or axles or anything like that it's an electronic type noise and its a clicking for about 6 seconds at a time???

 

[McFizzl]

Running the a/c? Could be the a/c clutch broke?

 

[SunlitComet]

sound more the the emissions air pump if you have one installed.