SERVICING
59
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 (S-301
and S-302). 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 thermo-
stat.
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 con-
trol.
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 sole-
noid. If no voltage present, check 6 pin connector
and wires from compressor unloader solenoid to 6
pin connector on board. If connector and wires
check good, replace control.
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 compressor unloader sole-
noid.
c. No voltage - check 6 pin connector and wires from
compressor unloader solenoid to 6 pin connector
on board. If connector and wires check good,
replace control.
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