Johnson Controls METASYS VAV110 Technical Manual page 84

84 VAV Controller—Variable Air Volume Controller
The green LED on the VAV110/111 and VAV140/141 Series Controllers
may be used to troubleshoot problems with the Zone Bus.
Table 37: Zone Bus LED Indications
LED Status
Off
On
Blinking
Indication
There is no power to the ASC.
The Zone Bus is shorted to Common or 24 VAC.
Normal communication is taking place.