Start Up & Auto A/C

[lelandstanford]

Normally, I leave HVAC in following setting:

Fan: 1
Temp: Coldest
Mode: Vent
Rec: Off
A/C :Off

Maybe I've never noticed before. After performed DEF mod, A/C compressor will engage briefly first engine start of the day. I didn't open hood to verify clutch engagement but I can hear the clutch engages and cool air blowing.

Is this normal for Delphi designed HVAC (with or without DEF mod) or something is going downhill?

A/C not kicked in.

[ASE_Master-Tech]

Normal for the a/c to cycle 'on' in defrost mode regardless of any other setting. This has 2 purposes, in the cold weather it aids in removing moisture from the cabin air, & it assures that the system runs occasionally to keep lubrication flowing around. Hope this was the answer you were looking for.

[lelandstanford]

The HVAC system has DEF mod so A/C compressor will not engage unless "A/C" button is ON.

The question is A/C compressor will engage briefly (like self test) when engine is started in the morning. HVAC default setting is: FAN=1, Mode=VENT, TEMP=COLDEST, AC=OFF and REC=OFF.