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2.3
Compressor Troubleshooting
NOTE: It is important to rule out other component failures before condemning the compressor.
The following electrical tests will aid diagnosis:
1. Start-Up Voltage: Measure the voltage at the compressor terminals during start-up. The voltage
must exceed the minimum shown in chart below, or compressor failure is likely. A low voltage
condition must be corrected.
2. Running Amperage: Connect a clip-on type ammeter to the (common) lead to the compressor.
Turn on the supply voltage and energize the unit. The compressor will initially draw high amperage;
it should soon drop to the RLA value or less. If the amperage stays high, check the motor winding
resistances.
NOTE: Feel the top of the compressor to see if it has overheated. If it is hot, the internal overload
may be open. You may have to wait several hours for it to reset.
3. Motor Winding Resistances: Using a digital volt-ohm meter (VOM), measure the resistance
across the compressor windings as shown below.
Resistance can be measured as shown above.
4. High Voltage/Insulation Test: Test internal leakage with a megoh meter. Attach one lead to the
compressor case on a bare metal tube and to each compressor terminal to test the motor windings.
A short circuit at high voltages indicates a motor defect. Do not do this test under vacuum.
2.4
Control Board Diagnosis
The control board (see section 1.6a for a complete description of the control board) has a red diagnostic
LED which indicates the lockout fault. The control board will enter into and indicate lockout if either
of the fault conditions (LPS or HPS) occur twice.
The contactor must be closed before the first fault condition can be recognized by the control board.
The contactor will be closed 3 minutes after the unit is energized and only if cooling is required. The
first fault condition will open the contactor and shutdown the unit. The contactor on the unit that has
the fault condition must be closed before the second fault condition can be recognized by the control
board. The contactor on the unit with the fault condition will close after 3 minutes if the unit is still
calling for cooling and if the fault condition no longer exists. If you get a second fault condition, the
contactor will open and shutdown the unit. The "red" led will have one blink if the high pressure switch
has opened twice and will have two blinks if the low pressure switch has opened twice. The unit must
be in the cooling mode (compressor contactor Closed) before a fault condition can occur.
Electrical Rating Designations*
Nominal Voltage
Phase
Minimum Voltage
Maximum Voltage
* Letters refer to model number code designations
Refer to page 10.
SINGLE
PHASE
R
2
S
23
208/230
197
253
C
R
> R
> R
R
3
2
1
1
R
= R
+ R
3
2
1
R
R
3
A
1
ECUA06 7/2014 new
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Table of Contents
Troubleshooting
