Daikin M Series Service And Troubleshooting page 42

SERVICING
L2
LOW
T1
K4
Q3
FS
T2
C9
U6
5
4
U7
3
U4
2
1 U3
U5
180
SPEED UP
150 NONE F1
120 5 MIN
SW1 90 10MIN
FAULT BLOWER STAGE
ECON
RECALL OFF DELAY DELAY
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.
INDUCER L1
OD F
PARK
LOW HIGH
HIGH
K6
K3 K5
K7
P2
U2
U1
K2
K1
R C W1W2 G Y1 Y2
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
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