Troubleshooting; Overview - Toshiba MMU-UP0051MH-E(TR) Service Manual

9. TROUBLESHOOTING

9-1. Overview

(1) Before engaging in troubleshooting
(a) Applicable models
All Super Modular Multi System (SMMS- ) models.
(Indoor units: MM -UP
(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)
N O .
A compressor would not start
1
An indoor fan would not start
2
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
CAUTION
The cooling performance may be declining considerably when total operating capacity of cooling indoor units
is less than 4 HP while ambient temperature is below.
(2) Troubleshooting procedure
When a problem occurs, proceed with troubleshooting in accordance with the procedure shown below.
Problem
Investigate check code
displayed on interface P.C. board
of header unit
NOTE
Rather than a product trouble (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.
, Outdoor units: MMY-M P
B e h a i v r o
• The air conditioner is being controlled by function of residual heat
"E28" check code
)
P
• The air conditioner is being controlled by the 3-minute protective function.
• It is in standby status though the room temperature has reached the setup
temperature.
• It is being operated in timer mode or fan mode.
• It is being in initial communication.
• The air conditioner is being controlled by the cool air discharge preventive
function in "heating"?
• The air conditioner is being operated in "cooling" under the low outside air
temperature.
• It is being operated in defrost operation.
elimination being performed as part of the air conditioner shutdown
process after heating operation.
• The air conditioner is being operated under external or remote controller.
Investigate check code
displayed on interface P.C.
board of relevant follower unit
Any other problem
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o s s b i e l c a u s e
Check the problem
site or problem part