SERVICING
13
The true suction should be the same as the suction line
after the valve. If there is a 4-degree difference, valve is
leaking. When stuck in the mid-position, part of the dis-
charge gas from the compressor is directed back to the
suction side, resulting in excessively high suction pressure.
An increase in the suction line temperature through the
reversing valve can also be measured. Check operation of
the valve by starting the system and switching the opera-
tion from COOLING to HEATING cycle. If the valve fails to
change its position, test the voltage (24V) at the valve coil
terminals (X25A) on outdoor unit PCB while the system is
on the COOLING cycle. If voltage is registered at the coil,
tap the valve body lightly while switching the system from
HEATING to COOLING, etc. If this fails to cause the valve
to switch positions, remove the coil connector cap and test
the continuity of the reversing valve solenoid coil. If the coil
does not test continuous - replace it. If the coil test continu-
ous and 24 volts is present at the coil terminals, the valve is
inoperative - replace it.
AVPEC* HEATER CONTROL (OPTIONAL)
DESCRIPTION
The AVPEC* models utilize an electronic control that pro-
vides ECM blower motor control and control of up to two
electric heat sequencers. The control has thermostat inputs
for variable stage of cooling/heating, two stages of electric
heat, reversing valve, and dehumidification. Control input is
24 VAC.
FEATURES
The new air handler control includes advanced diagnostic
features with fault recall, estimated CFM display via 7
segment display of control board, CoolCloud
TM
ready.
Diagnostics includes heater kit selection diagnostics, open
fuse, internal control fault, data errors, and blower motor
faults. Data errors are not included in the fault recall list.
Diagnostic error codes are displayed on a single red LED.
The estimated CFM is displayed on an on-board 7 segment
display. For example, if the CFM is 1240 CFM, 7 segment
display shows “FC...A...12...40...”.
The AVPEC* air handlers may be used in a fully communi-
cating system when matched with a compatible outdoor unit
and the thermostat. A fully communicating system offers
advanced setup and diagnostic features.
BASIC OPERATION
The air handler control receives operation demand inputs
from the thermostat. The control operates the variable
speed blower motor at the demand as determined from the
thermostat input(s). If a demand for electric heat is re-
ceived, the control will provide a 24VAC output for up to two
electric heat contactors.
TROUBLESHOOTING
MOTOR CONTROL CIRCUITS
WARNING
HIGH VOLTAGE
Disconnect ALL power before servicing or in-
stalling this unit. Multiple power sources may
be present. Failure to do so may cause proper-
ty damage, personal injury or death.
1. Turn on power to air handler or modular.
WARNING
Line voltage now present.
2. Check voltage between pins 1 and 4 at the 4-wire
motor connector on the control board. Voltage should
be between 9 and 15 VDC. Replace control if voltage
is not as specified.
ELECTRIC HEAT SEQUENCER OUTPUTS
WARNING
HIGH VOLTAGE
Disconnect ALL power before servicing or in-
stalling this unit. Multiple power sources may
be present. Failure to do so may cause proper-
ty damage, personal injury or death.
1. Turn on power to air handler or modular blower.
WARNING
Line voltage now present.
2. Disconnect the 3-circuit harness connecting the con-
trol to the electric heater kit.
3. Provide a thermostat demand for low stage auxiliary
heat (W1). Measure the voltage between pins 1 and
3 at the on-board electric heat connector. Voltage
should measure 24VAC. Replace control if no voltage
is present.
NOTE:
Allow for any built-in time delays before making
voltage measurements. Any electric heater faults that are
present may prevent the heater output from energizing. Ver-
ify that no heater faults are present before making voltage
measurements.
