Troubleshooting; Overview - Toshiba MMU-UP0091HP-E 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 the 3-minute protective function.
• It is in standby status though the room temperature has reached the setup
• 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
• The air conditioner is being operated in "cooling" under the low outside air
• It is being operated in defrost operation.
• The air conditioner is being controlled by function of residual heat
• The air conditioner is being operated under external or remote controller.
"E28" check code
)
P o s
temperature.
function in "heating"?
temperature.
elimination being performed as part of the air conditioner shutdown
process after heating operation.
Investigate check code
displayed on interface P.C.
board of relevant follower unit
Any other problem
- 124 -
s b i e l c a u s e
Check the problem
site or problem part