44
ST 5220
QM 1336.rev.01
CAUSE
SOLUTION
PROBLEM
The display
shows sudden
variations in the
room or outside
temperature.
A variation in resist-
ance is induced on a
probe.
Be sure the probes are dry.
Locate them away from drafts
and sources of radiant heating.
Be sure the outside probe is
installed correctly. Refer to
"Installing the outside probe"
There is electrical
noise near a probe
cable.
Isolate the probe cables from all
high voltage sources. Do not
route probe cables and other
power cables through the same
electrical knockout. Do not run
probe cables next to other
power cables. When crossing
other power cables, cross at
90°.
The stage 1 or 2
variable speed
cooling fans are
not running.
Correct the wiring. Be sure two
different lines are connected to
each fan motor: line L1 modu-
lated by the controller should be
combined with another line (N
for 115V or L2 for 230V) to
activate the motor. Also, be sure
the stage 1 COMMON is supplied
by line L1.
The wiring is incor-
rect.
Correct the problem and replace
the fuse.
The stage 1 fuse is
open.
The display board
interconnect cable is
not properly plugged
into the power supply
board.
Be sure the cable is firmly
plugged in.
