37
ComPac 9/04-12
1. Obstruction in condensate line.
2. Obstruction or leak in conden-
sate pan.
3. Unit is not level.
1. Check for clog or restriction.
2. Check pan for leak or blockage.
3. Level unit.
E. Water on floor near unit.
PROBLEM / SYMPTOM
LIKELY CAUSE(S)
CORRECTION
1. Check resistance element(s) for
continuity.
2. Check continuity across thermal
limit switch.
3. Check relay for proper operation.
Replace if defective.
4. Check across TCO (adjacent to
element(s)) for continuity. It is
normally closed.
1. Defective heating element(s).
2. Thermal limit open.
3. Defective heater relay.
4. Open thermal cut-out (TCO).
F. No space heating or reduced
heating (units equipped with
resistance elements)
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 Table 5, section
2.2, 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. Any deviation from above
values could indicate a defective compressor.
4. High Voltage/Insulation Test: Test internal leakage with a megohmeter.
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.
4.3 C
OMPRESSOR
T
ROUBLESHOOTING
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
