2021 Tahoe RST Duramax LOUD ticking sound before starting car, “climate system defogging reduced” notification

[msnyder724]

I just got our Tahoe a year ago. It has been serviced back in May. This sound has been on and off since then, but now is very consistent. It is so loud and will last from 30 seconds to 2 minutes. It will stop after driving a certain speed. I’ve noticed a slow oil leak for the last two days. The sound is more prominent on passenger side. A “service climate system defogging reduced” notification popped up yesterday. Anyone know what this may be? AC unit?

 

[Doubeleive]

sounds like ac pump, you can take the belt off and see if the noise is gone, take it to the dealer it should be under warranty.

 

[steiny93]

loud ticking before you start? does it always happen or just when you get into the vehicle? where is it coming from? seems like the dealer should be able to find the source if it lasts for a couple minutes

 

[suterusu]

Loud ticking combined with defogging/climate error would lead me to believe their is an issue with the A/C compressor clutch. The clicking is probably the clutch/solenoid that engages the compressor going through a pre-startup check.