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38MGRBQ: Service Manual
TROUBLESHOOTING
This section provides the required flow charts to troubleshoot problems.
NOTE: Information required in the diagnoses can be found either on
the wiring diagrams or in the appendix.
Required Tools:
The following tools are needed when diagnosing the units:
• Digital multimeter
• Screw drivers (Phillips and straight head)
• Needle-nose pliers
• Refrigeration gauges
Recommended Steps
1. Refer to the diagnostic hierarchy charts below and determine the
problem at hand.
2. Go to the chart listed in the diagnostic hierarchy and follow the steps
in the chart for the selected problem.
For the ease of service, the systems are equipped with diagnostic code
display LED's on both the indoor and outdoor units. The outdoor
diagnostic display is on the outdoor unit board and is limited to very
few errors. Refer to the Indoor Unit's Service Manual to determine the
error code display method. If possible always check the diagnostic codes
displayed on the indoor unit first.
Problems may occur that are not covered by a diagnostic code, but are
covered by the diagnostic flow charts. These problems are typical air
conditioning mechanical or electrical issues that can be corrected using
standard air conditioning repair techniques.
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
For problems requiring measurements at the control boards, note the
following:
1. Always disconnect the main power.
2. When possible check the outdoor board first.
3. Start by removing the outdoor unit top cover.
4. Reconnect the main power.
5. Probe the outdoor board inputs and outputs with a digital multi-
meter referring to the wiring diagrams.
6. Connect the red probe to hot signal and the black probe to the ground
or negative.
7. Note that some of the DC voltage signals are pulsating voltages for
signal. This pulse should be rapidly moving at all times when there
is a signal present.
8. If it is necessary to check the indoor unit board, you must start by
disconnecting the main power.
9. Remove the front cover of the unit and then control box cover.
10. Carefully remove the indoor board from the control box. Place it
face up on a plastic surface (not metal).
11. Reconnect the main power and repeat steps 5, 6, and 7.
12. Disconnect the main power before reinstalling the board to avoid
shock hazard and board damage.
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