19
INSTALLER’S GUIDE
18-HE39D8-13A-EN
Is OD ambient
Dampers will not open
beyond minimum
position during 1
st
stage cooling.
below 70F?
Wires are
Ensure wires from
"1" and "TR1" are
correctly wired to
unit's low voltage
leads.
correctly
applied?
Remove wires
from "T" and "T1"
Replace MAS
Correct wiring.
Ambient must be below 70F to activate
economizer beyond minimum position fresh
air opening.
Is OAS closed?
Is 24V present
between
terminals "1" and
"TR1"
Is resistance
Remove OAS
wire from "S0"
and "+" terminals
on the Logic
module
What is
620 ohms?
No
Replace the 620 ohm
1 watt resistor.
resistance of
MAS
2-4 ohms
Replace Actuator and Logic
Module
Measure
resistance across
wire leads
Jumper across the
OAS terminals to
close circuit
Does economizer
now operate?
Replace OAS
Yes
Yes
Yes
Yes
No
No
No
No
No
Yes
Honeywell W7459 Only - Troubleshooting - Unit Will Not Economize
