Daikin M Series, Service And Troubleshooting

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SERVICING
42
L2
INDUCER
LOW HIGH
L1
OD F
LOW HIGH
T1
Q3
K4
K3 K5
K6
T2
K7
FS
U1
U2
U6
U7
U4
U5
U3
P2
K2
K1
ECON
STAGE
DELAY
C9
SPEED UP
SW1
FAULT
RECALL
BLOWER
OFF DELAY
F1
R C W1W2 G Y2
90
120
150
180
10MIN
5 MIN
NONE
PARK
1
2
3
4
5
Y1
PCBAG127 DSI Control Board
Testing Direct Spark Ignition (DSI) Systems
PCBAG127 Board
Heating Mode
Indoor thermostat calling for heat (15 second prepurge time
and 7 second trial for ignition).
1. Check for 230 volts from L1 terminal of control
module to L2. No voltage - check wire connections,
continuity, etc.
2. Check for 24 volts at “R” to “C” thermostat terminals.
A. No voltage - check 3 amp automotive type fuse
on control board. A blown fuse could indicate
a short in the 24 volt circuit (thermostat or limit
circuit).
B. Voltage Present - check limit and rollout. If limit
and rollout are closed, then check for 24 VAC at
the gas valve terminals.
C. No 24 VAC at gas valve - check 9 pin connector
and wires from ignition control to gas valve. If
wires and connections at 9 pin connector check
good, replace ignition control.
D. Voltage present at gas valve - replace gas
valve.
Testing High Stage Heat Operation with Low Stage
Heat Operating:
1. Board set for 2 stage thermostat:
A. Check for 24 Volts at thermostat terminals W2
and C on the control board.
B. No voltage - check thermostat and thermostat
wiring.
C. Voltage present - check for 24 volts at gas valve
terminals C and HI.
D. No voltage present at valve - check 9 pin
connector and wires from ignition control to gas
valve. If wires and connections at 9 pin connector
check good, replace ignition control.
E. Voltage present at gas valve - replace gas
valve.
2. Board set for 1 stage thermostat:
A. Wait the selected delay time (either 5 or 10
minutes, depending on jumper setting).
B. Check for 24 volts at gas valve terminals C and
HI.
C. No voltage present - check 9 pin connector and
wires from ignition control to gas valve. If wires
and connections at 9 pin connector check good,
replace ignition control.
D. Voltage present at gas valve terminals C and HI -
replace valve.
Cooling Mode
Indoor thermostat calling for cool.
1. Check for 230 volts from L1 terminal of control
module to L2. No voltage - check wire connections,
continuity, etc.
2. Check for 24 volts at R and C thermostat terminals
on ignition control.
A. No voltage - check 3 amp automotive type fuse
on control board. A blown fuse could indicate a
short in the 24 volt circuit.
B. Voltage present - proceed to step 3.
3. Check for 24 volts at thermostat terminals C and Y1.
A. No voltage - check thermostat wiring and
thermostat.
B. Voltage present - check pressure switch circuit.
If pressure switch circuit checks closed, proceed
to step 4.
4. Check for 24 volts at contactor coil.
A. No voltage - check 6 pin connector and wires
from contactor coil to 6 pin connector on control
board. If wires and connector check good,
replace control.
B. Voltage present - replace contactor.
Testing High Stage Cooling Operation with Low
Stage Cooling Operating:
1. Board set for 2 stage thermostat:
A. Check for 24 volts at thermostat terminals C and
Y2 on control board.
B. No voltage - check thermostat and thermostat
wiring.
C. Voltage present - check pressure switch circuit. If
pressure switch circuit checks closed, proceed to
next step.
D. Check for 24 volts to compressor unloader
solenoid. If no voltage present, check 6