Troubleshooting - Carrier 38MBR series Service Manual

TROUBLESHOOTING

This section provides the required flow charts to troubleshoot
problems that may arise.
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:
S Digital multimeter
S Screw drivers (Phillips and straight head)
S Needle−nose pliers
S 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. The indoor diagnostic display is a
combination of flashing LED's on the display panel on the front of
the unit. If possible always check the diagnostic codes displayed on
the indoor unit first.
The diagnostic codes for the indoor and outdoor units are listed in
the appendix.
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.
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 Next 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 main power before reinstalling board to avoid
shock hazard and board damage.
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