Q3 & Qht Controls for Direct Expansion Systems General System Troubleshooting
L-2516 ENGLISH 17
5. Check for a steady solid stream of water from the overboard discharge. If more than one unit is installed, then check all
such discharges.
6. Verify that there is steady airflow out of the supply-air grille.
7. Allow unit to run for ten minutes at high fan speed. Check the temperature differential between discharge and return air
by placing an accurate thermometer in front of the discharge grill and then in front of the return air grill.
In Cool Mode the difference between the discharge and return should be 15 - 20°F (8.3 - 11.1°C), with normal ambient
air and water temperatures.
In Heat Mode the differential can be as high as 25°F (13.9°C).
If the unit does not appear to be operating properly, refer to the guidelines in “TROUBLESHOOTING” on page 17.
TROUBLESHOOTING
GENERAL SYSTEM TROUBLESHOOTING
Before you call for service, review this list. It may save you time and expense. This list contains common occurrences that are
not a result of defective workmanship or materials. If you need service after trying these procedures, call your nearest Dometic
dealer.
See additional troubleshooting information in the manual for your specific air conditioning system. See also “Digital-Controls
Troubleshooting” on page 20.
IMPORTANT
Do not turn the unit off then immediately turn it back on. Allow at least 30 seconds for refrigerant pressure to equalize.
Table 6: General System Troubleshooting
PROBLEM POSSIBLE REASON/SOLUTION
System will not start. 1. Air conditioner circuit breaker is off. Turn circuit breaker on at ship’s panel.
2. Digital control is not turned on. Press the Power button.
3. Wrong wiring at terminal strip. Check wiring diagram; correct if necessary.
4. Input-line voltage is insufficient. Check power source (shore/generator) for proper
voltage. Check wiring and terminals for proper sizes and connections. Verify with a
volt-meter that the power at the unit is the same as the power source.
5. Push-on connectors or butt splices became disconnected during installation.
Disconnect power supply and open electric box, check wiring diagram, correct if
necessary.
System runs continuously. 1. Set point temperature is improperly set: too low for cooling or too high for
heating. Raise or lower set point.
2. Porthole or hatches open. Close all port holes and hatches.
3. Improper air sensor location. Check your specific control troubleshooting section.
4. Seawater temperature too high for cooling or too low for heating. Seawater
temperature will directly affect the air conditioning unit’s efficiency. This air
conditioning unit can effectively cool your boat in water temperatures up to 90°F
(32.2°C) and heat (if reverse cycle option is installed) in water as low as 40°F (4.4°C).
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