Marvair 8AA1024A-1060A & 8AA2036A-2060A I&O Manual
05/2023 Rev.3
47
3.
Motor Winding Resistances:
Using a digital volt-ohm meter (VOM), measure the resistance across
the compressor windings as shown below.
C
S
R
R
2
R
1
R
3
SINGLE
PHASE
R
3
> R
2
> R
1
R
3
= R
2
+ R
1
T
1
T
2
T
3
R
2
R
1
R
3
THREE
PHASE
R
3
= R
2
= R
1
Resistance can be measured as shown above. Any deviation from above values could indicate a
defective compressor.
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.
5. On single phase models, check the capacitor by substitution.
5.4 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.
