57
R e s i d e n t i a l D i g i t a l H & V - Tr a n q u i l i t y
®
2 2 D i g i t a l ( T Z ) S e r i e s - 6 0 H z H F C - 4 1 0 A
C r e a t e d : 2 6 O c t . , 2 0 1 1 B
c l i m a t e m a s t e r. c o m
General
If operational dif
fi
culties are encountered, perform
the preliminary checks below before referring to the
troubleshooting charts.
• Verify that the unit is receiving electrical supply power.
• Make sure the fuses in the fused disconnect switches are
intact.
After completing the preliminary checks described above,
inspect for other obvious problems such as leaking
connections, broken or disconnected wires, etc. If everything
appears to be in order, but the unit still fails to operate
properly, refer to the “DXM2 Troubleshooting Process
Flowchart” or “Functional Troubleshooting Chart.”
DXM2 Board
DXM2 board troubleshooting in general is best summarized
as verifying inputs and outputs. After inputs and outputs
have been veri
fi
ed, board operation is con
fi
rmed and the
problem must be elsewhere. Below are some general
guidelines for troubleshooting the DXM2 control.
Field Inputs
Conventional thermostat inputs are 24VAC from the
thermostat and can be veri
fi
ed using a voltmeter between C
and Y1, Y2, W, O, G. 24VAC will be present at the terminal
(for example, between “Y1” and “C”) if the thermostat is
sending an input to the DXM2 board.
Proper communications with a thermostat can be veri
fi
ed
using the Fault LED on the DXM2. If the control is NOT
in the Test mode and is NOT currently locked out or in
a retry delay, the Fault LED on the DXM2 will
fl
ash very
slowly (1 second on, 5 seconds off), if the DXM2 is properly
communicating with the thermostat.
Sensor Inputs
All sensor inputs are ‘paired wires’ connecting each
component to the board. Therefore, continuity on pressure
switches, for example can be checked at the board
connector. The thermistor resistance should be measured
with the connector removed so that only the impedance of
the thermistor is measured. If desired, this reading can be
compared to the thermistor resistance chart shown in Table
8. An ice bath can be used to check the calibration of the
thermistor.
Outputs
The compressor and reversing valve relays are 24VAC
and can be veri
fi
ed using a voltmeter. For units with ECM
blower motors, the DXM2 controls the motor using serial
communications, and troubleshooting should be done with
a communicating thermostat or diagnostic tool. The alarm
relay can either be 24VAC as shipped or dry contacts for use
with DDC controls by clipping the JW1 jumper. Electric heat
outputs are 24VDC “ground sinking” and require a voltmeter
set for DC to verify operation. The terminal marked “24VDC”
is the 24VDC supply to the electric heat board; terminal
“EH1” is stage 1 electric heat; terminal “EH2” is stage 2
electric heat. When electric heat is energized (thermostat
is sending a “W” input to the DXM2 controller), there will
be 24VDC between terminal “24VDC” and “EH1” (stage 1
electric heat) and/or “EH2” (stage 2 electric heat). A reading
of 0VDC between “24VDC” and “EH1” or “EH2” will indicate
that the DXM2 board is NOT sending an output signal to the
electric heat board.
Test Mode
Test mode can be entered for 20 minutes by pressing the
Test pushbutton. The DXM2 board will automatically exit test
mode after 20 minutes.
Advanced Diagnostics
If a communicating thermostat or diagnostic tool is
connected to the DXM2, additional diagnostic information
and troubleshooting capabilities are available. The current
status of all DXM2 inputs can be veri
fi
ed, including the
current temperature readings of all temperature inputs.
With a communicating thermostat the current status of the
inputs can be accessed from the Service Information menu.
In the manual operating mode, most DXM2 outputs can
be directly controlled for system troubleshooting. With a
communicating thermostat the manual operating mode can
be accessed from the Installer menu. For more detailed
information on the advanced diagnostics of the DXM2, see
the DXM2 Application, Operation and Maintenance (AOM)
manual (part #97B0003N15).
DXM2 Troubleshooting Process Flowchart/Functional
Troubleshooting Chart
The “DXM2 Functional Troubleshooting Process Flowchart”
is a quick overview of how to start diagnosing a suspected
problem, using the fault recognition features of the DXM2
board. The “Functional Troubleshooting Chart” on the
following page is a more comprehensive method for
identifying a number of malfunctions that may occur, and is
not limited to just the DXM2 controls. Within the chart are
fi
ve columns:
• The “Fault” column describes the symptoms.
• Columns 2 and 3 identify in which mode the fault is likely
to occur, heating or cooling.
• The “Possible Cause column” identi
fi
es the most likely
sources of the problem.
• The “Solution” column describes what should be done to
correct the problem.
WARNING!
HAZARDOUS VOLTAGE! DISCONNECT
ALL ELECTRIC POWER INCLUDING REMOTE
DISCONNECTS BEFORE SERVICING.
Failure to disconnect power before servicing can cause
severe personal injury or death.
Troubleshooting
WARNING!
