25

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:
SDigital multimeter
SScrew drivers (Phillips and straight head)
SNeedle--nose pliers
Recommended Steps
1. Refer to the diagnostic hierarchy chart 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.

DIAGNOSTIC HIERARCHY

Unit has a problem
Unit displays a
diagnostic code
Unit not running and
no diagnostic code
Unit running but not
optimally
Refer to page ---
appropriate diagnostic chart
Go to chart # 7 Go to chart # 8 & 9
* For EEROM error, replace the indoor microprocessor board
Unit has a problem
Unit displays a
diagnostic code
Unit not running and
no diagnostic code
Unit running but not
optimally
Refer to page A8 & A9
identify error code* and use Go to chart Go to chart #
* For EEROM error, replace the indoor microprocessor board
A08165
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 an LED on the outdoor unit board
and is limited to very few errors. However, it is useful in
identifying special error codes like a failure of the outdoor coil
sensor on heat pumps. 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
appendix A8 and A9.
Problems may occur that are not covered by a diagnostic code, but
are covered by the diagnostic flow charts starting with the
diagnostic hierarchy. These problems will be 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 please
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 and
input/output charts found in the appendix.
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 pulse will give
continuously variable readings.
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.
38/40MVC, MVQ