20
INSTALLER’S GUIDE
18-HE39D8-13A-EN
Is a 2-stage
Compressor will not
energize when
space conditions
rise.
thermostat
applied?
Is thermostat's Y2
connected to unit's YL
Yes
Is 24V present at YL
Troubleshoot unit. Problem
is not in economizer.
Troubleshoot why
thermostat is not calling
for 2
nd
stage.
Wire per Installer's
Guide.
Install a 2 stage thermostat and
wire according to economizer
Installer's Guide
No
No
No
Yes
Honeywell W7459 Only - Troubleshooting - 2nd Stage Inoperable