ClimateMaster DC Series Installation Manual download pdf (Page 45)

Residential H&V - 60Hz R22 &R410A

Rev.: 22 Dec, 2008

climatemaster.com

General

If operational difﬁ 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 “CXM Troubleshooting Process

Flowchart” or “Functional Troubleshooting Chart.”

CXM Board

CXM board troubleshooting in general is best summarized

as simply verifying inputs and outputs. After inputs and

outputs have been veriﬁ ed, board operation is conﬁ rmed and

the problem must be elsewhere. Below are some general

guidelines for troubleshooting the CXM control.

Field Inputs

All inputs are 24VAC from the thermostat and can be veriﬁ ed

using a volt meter between C and Y, G, O, W. 24VAC will be

present at the terminal (for example, between “Y” and “C”) if

the thermostat is sending an input to the CXM board.

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

the CXM AOM manual. An ice bath can be used to check

calibration of the thermistor.

Outputs

The compressor relay is 24VAC and can be veriﬁ ed using a

voltmeter. The fan signal is passed through the board to the

external fan relay (units with PSC motors only). 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 volt meter

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 CXM 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 CXM board

is NOT sending an output signal to the electric heat board.

Test Mode

Test mode can be entered for 20 minutes by shorting the test

pins. The CXM board will automatically exit test mode after

20 minutes.

CXM Troubleshooting Process Flowchart/Functional

Troubleshooting Chart

The “CXM Troubleshooting Process Flowchart” is a quick

overview of how to start diagnosing a suspected problem,

using the fault recognition features of the CXM 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

CXM 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 likey to

occur, heating or cooling.

• The “Possible Cause column” identiﬁ 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! 

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ClimateMaster DC Series Installation Manual Page 45

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