Troubleshooting; Overview - Toshiba MMD-AP0186HP-EU Service Manual

9. TROUBLESHOOTING

9-1. Overview

(1) Before engaging in troubleshooting
(a) Applicable models
All Super Module Multi (SMMS, SHRM, Mini-SMMS, SMMS-i) models.
(Indoor units: MMO-APOOO, Outdoor units: MMY-MAPOOOO*, MCY-MAPOOOHT*)
(b) Tools and measuring devices required
• Screwdrivers (Philips, flat head), spanners, long-nose pliers, nipper, pin to push reset switch, etc.
• Multimeter, thermometer, pressure gauge, etc.
(c) Things to check prior to troubleshooting (behaviors listed below are normal)
NO.
A compressor would not start
1
2 An indoor fan would not start
An outdoor fan would not start or would
3
change speed for no reason
An indoor fan would not stop
4
The air conditioner would not respond to a
5
start / stop command from a remote controller
(2) Troubleshooting procedure
When a fault occurs, proceed with troubleshooting in accordance with the procedure shown below.
Fault Investigate check code displayed
on interface P.C. board of header
unit
NOTE
Rather than a genuine fault (see the List of Check Codes below), the problem could have been caused by a
microprocessor malfunction attributable to a poor quality of the power source or an external noise. Check for
possible noise sources, and shield the remote controller wiring and signal wires as necessary.
Behavior
"E28" error
• Could it just be the 3-minute delay period
(3 minutes after compressor shutdown)?
• Could it just be the air conditioner having gone thermo OFF?
• Could it just be the air conditioner operating in fan mode or put on the timer?
• Could it just be the system going through initial communication?
• Could it just be cold air discharge prevention control, which is part of heating?
• Could it just be cooling operation under low outside temperature conditions?
• Could it just be defrosting operation?
• Could it just be the elimination of residual heat being performed as part of
the air conditioner shutdown process after heating operation?
• Could it just be the air conditioner operation under external or remote
controller?
Investigate check code
displayed on interface P.C.
board of relevant follower unit
Any other fault
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Possible cause
Check fault site or
faulty part